EP1179106B1

EP1179106B1 - Cage former and clamp therefor

Info

Publication number: EP1179106B1
Application number: EP00901826A
Authority: EP
Inventors: Stephen Render
Original assignee: Rom Ltd
Current assignee: Rom Ltd
Priority date: 1999-01-27
Filing date: 2000-01-26
Publication date: 2006-04-05
Anticipated expiration: 2020-01-26
Also published as: DE60027150D1; AU2312500A; GB9901746D0; EP1179106A1; WO2000045008A1

Description

FIELD OF THE INVENTION

This invention relates to a cage former and clamp therefor, and in particular to a cage former for use in assembling and maintaining a pile cage for a reinforced concrete pile.

BACKGROUND TO THE INVENTION

Reinforced concrete piles are known for use in the foundations of roadway bridges and the like. The piles are sunk deep into the ground and can for example provide a link between the bridge supports and the underlying rocks.
The cage typically comprises a number of cage bars which in use are arranged to lie substantially along the longitudinal axis (usually a vertical axis) of the pile. The bars are interconnected so as to maintain their separation and alignment. The bars can be interconnected by a helical wire, by one or more frames arranged at intervals along the length of the cage bars, or both.
The cage acts both as a reinforcement for the concrete and also as a means to tie the bridge support or the like to the pile. To achieve the latter purpose, it is common-place for the cage bars to project beyond the end or top of the pile.
In order to maintain the integrity of the pile it is necessary to ensure that the metal cage bars (and also the metal of the frames or interconnecting wire) do not encroach too near the surface of the concrete, and it is recognised that a "cover zone" is required within which either no metal, or only metal which is protected against corrosion, should be present. The cover zone will typically comprise a layer several centimeters thick adjacent the surface of the concrete.
Should unprotected metal encroach into the cover zone there is a risk that over time water and other agents will contact the metal and cause it to corrode, eventually breaking down parts of the pile. It is usually uneconomic to manufacture the whole pile cage from protected metal such as stainless steel or otherwise corrosion resistant metal, and so the manufacturers of piles and pile cages therefore seek to ensure that any metal which is present in the cover zone is protected, usually by a plastic coating or sheathing.

DESCRIPTION OF THE PRIOR ART

It is known to provide a rigid structure comprising one or more polygonal or substantially circular frames to which the cage bars can be secured, the rigid structure being referred to herein as a cage former. It is known to affix cage formers at predetermined locations along the length of the cage, and to use these in combination with a helical interconnecting wire.
European patent application 0 608 068 discloses a cage former having two frames which are joined rigidly together by a number of outwardly-flared rods. This cage former can serve to interconnect and locate the cage bars relative to one another. The cage former also has integral spacer means to ensure that the assembled cage is kept out of the cover zone, the spacer means being provided by the outwardly flared portions of the rods interconnecting the two frames, each of which carries a plastic sleeve.
Typically, a cage will be assembled on site prior to insertion into the hole prepared for the pile. During the assembly, the cage bars are secured to the helical wire and/or to the cage former(s). US Patent 4,463,538 discloses a reinforcement cage having circular frames which act as cage formers, which frames are secured to the cage bars by way of spring clips. Alternatively, the cage bars are secured to the helical wire or cage former(s) by way of wire ties located at the junctions therebetween, the wire ties being sufficiently strong and sufficiently numerous to maintain the structural integrity of most of the cage as it is moved about the site.
However, the cage must usually be lifted in order to move it about the site, and also to lower it into the prepared hole. Since an assembled cage can be of considerable weight, the spring clips or wire ties are not always sufficiently strong to provide lifting points for the cage. Thus, to lift the cage it is necessary to affix a line or cable to the cage, typically to a pair of junctions of a particular cage former and the corresponding cage bars. If the chosen junctions are maintained only by a spring clip or wire tie they will usually be unable to support the weight of the cage, and the cage bars will be forced to slide relative to the cage former, and vice versa, so that the structural integrity of the cage is lost.
To overcome this problem, it is known to secure a frame of a cage former to the cage bars by way of U-bolts at certain junctions, those junctions subsequently being used as the lifting points for the cage. The U-bolts are able to maintain the structural integrity of the particular junctions, and the wire ties can maintain the structural integrity of the remaining junctions since these are not required to support the weight of the cage.
However, the use of such U-bolts has significant disadvantages. Firstly, since a fitted U-bolt surrounds both of the frame and cage bar part of the U-bolt may lie within the cover zone. Secondly, the bolts which are required to be tightened typically lie within the cage, and so may be difficult to access with a spanner or the like. Thus, an assembled pile cage comprises a matrix of longitudinal cage bars and transverse frames (and a helical wire), and access through a gap in the matrix to tighten a nut upon the U-bolt can be very awkward and may not always be achieved satisfactorily, resulting in a junction which cannot support the weight of the cage when this is lifted. It is of course possible to fit the U-bolt with the free ends of the bolts projecting outwardly so that access to the nuts is substantially unhindered, but this is seldom preferred since the likelihood of metal entering the cover zone is considerably increased by such practice. A third disadvantage of such an arrangement is that the U-bolts are supplied separately from the remainder of the cage components, and perhaps from a different supplier; the failure of the U-bolt supplier to deliver the U-bolts in time, or the loss of those U-bolts on site, will result in a delay to the pile construction.
European patent application 0 881 337 discloses a clamping device for use with reinforcing bar. It is disclosed that the clamping device can be used in a reinforcing cage by welding the device to a reinforcing bar or to a part of a cage former.
GB patent application 2,310,875 discloses a cage former having two frames which are rigidly joined together. Two clamps, such as scaffolding clamps, are secured to the inside surface of one of the frames. Accordingly, this cage former overcomes the third disadvantage mentioned above in that the clamp is supplied with and secured to the cage former. The clamps are secured to the frame and have a pivotable flap which can surround the cage bar and secure this to the frame by way of a tightenable bolt.
Notwithstanding its advantages over the prior art U-bolts, this cage former also has a number of disadvantages. With this cage former also, the free end of the bolt projects towards the centre of the cage, and so it shares the second disadvantage of a U-bolt arrangement as outlined above. In addition, whilst the drawings of this document show a clamp in which the cage bar lies against a part of the frame, in practice a scaffolding clamp is used having a body which is welded to the inside surface of the frame; in the assembled cage the cage bar lies against the body and does not directly engage the frame at all.
With the practical embodiment described above, in which the body of the clamp lies between the cage bar and the frame, the cage bar is spaced from the frame by as much as 15 mm. Since it is customary for the clamps to be fitted to radially opposite cage bars, the cage bars to which the clamps are fitted can therefore be up to 30 mm closer together than would be necessary without the clamps.
It is understood by those skilled in the art that the separation of the cage bars on opposite sides of the cage should ideally be maximised, since this provides the maximum lever arm and so the maximum transverse loading which the cage and thus the assembled pile can withstand. The designer of the pile will usually design the cage to meet its specification when all of the cage bars lie within but in engagement with the frame(s), and the reduced separation of opposed cage bars at one or more locations along the length of the cage might reduce the cage's ability to withstand transverse loading.
In addition, the use of clamps is usually only required at certain positions along the length of the cage, the number of clamping positions being determined by the size of the cage. Only a single clamping position (providing two opposed lifting points) may be required for a small cage, for example. Away from this position (or these positions, as applicable) the cage bars will be secured to the frame(s) and helical wire by wire ties. It is thus necessary for the cage bars which are clamped to bend to accommodate the fact that for the majority of their length they are at the specified position (in contact with the frame and/or helical wire), but at the particular position or positions are forced to deviate towards the centre of the cage by as much as 15 mm. This can of course make it difficult effectively to tie the cage bar to the frames or helical wire close to the clamps, so that the structural integrity of the cage might be impaired.
Furthermore, if the clamp position is chosen to be at one end of the cage, the cage bars which engage the clamps will converge towards the end of the cage, i.e. there is no facility to force them to diverge back towards the specified position; if the cage bars extend beyond the end of the cage, for example for securement to a bridge support or the like, then the convergence of certain of the cage bars can be a significant disadvantage.

STATEMENT OF THE INVENTION

It is the object of the present invention to seek to reduce or avoid the disadvantages with the known cage formers, and in particular with the form and arrangement of the clamps which are fitted thereto.
According to the invention therefore, there is provided a cage former for use in a pile cage, the cage former including a frame and a clamping means for clamping a cage bar to the frame so as to provide a secure junction between the frame and the cage bar, the junction being secure enough to act as a lifting point for the pile cage, characterised in that the clamping means lies to the side of the frame.
Since the clamping means lies to the side of the frame no part of it lies between the frame and the cage bar in use, so that the cage bar can engage the frame and is not forced to deviate away from its specified position. Thus, the transverse loading which the assembled pile can withstand is not artificially reduced from its design loading.
With a substantially planar frame the clamping means lies outside the plane and outside the enclosed volume of the frame.
Preferably, there are two clamping means arranged at opposed positions on the frame. In such an embodiment, the separation between the cage bars secured to the clamps is maintained as specified.
Usefully, the clamping means comprises a body, a flap, a bolt and a nut. Usefully also the flap is pivotably connected to the body. Desirably, the flap has an aperture through which a part of the bolt can pass, the head of the bolt being retained by the flap. Desirably also, the body has a bifurcated section which can receive the free end of the bolt and against which the nut can be tightened to reduce the area enclosed by the clamping means, and in use to clamp a cage bar to the frame.
Preferably, the body of the clamp is secured to the side of the frame, as by welding. With the body secured to the frame, and the flap retaining the head of the bolt, it can be arranged that in the assembled cage the free end of the bolt projects towards the outside of the cage. In this way, the nut can be applied to the bolt and tightened thereon from outside the cage, without requiring access to the inside of the cage. In addition, the arm preferably surrounds a smaller sector of the cage bar than does the body. Preferably, the bolt is angled at a acute angle to the radius of the cage and neither the nut nor the free end of the bolt will enter the cover zone, even when the nut is fully tightened.
The inventor has therefore realised that placing the clamp alongside the frame allows considerable design freedom in the positioning of the bolt and nut, so that these components can be positioned to provide maximum ease of tightening whilst ensuring that no metal enters the cover zone.
Desirably, connected to the body of the clamping means is one or more support members which can overlie a part of the frame for the purpose of adding rigidity to the assembled frame and clamping means. Part of the support means may overlie a part of the inside surface of the frame (i.e. lie within the enclosed volume of a substantially planar frame), but this is of no detriment since the support means will not lie between the frame and the cage bar in use.
Usefully, at least part of the body and/or flap are of curved or substantially circular cross-section. As will readily be understood by those skilled in the art, the cage bars are typically of a construction known as reinforcing bar, in which the surface is "roughened" by way of raised longitudinal and transverse ribs. The provision of a curved or substantially circular body and/or flap permits the parts of the clamp which engage the cage bar to lie between adjacent ribs, and in particular to lie between adjacent transverse ribs, so increasing the effectiveness of the clamp thereon.
There is also provided a clamp for securement to a frame so as to provide a cage former as herein defined.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Fig.1: is a plan view of a cage former according to the invention;
Fig.2: is a view of part of the frame, and the body of the clamping means having two support members connected thereto;
Fig.3: is a plan view of the flap of the clamping means; and
Fig.4: is a sectional view along the lines IV-IV of Fig.2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The cage former 10 comprises a substantially circular frame 12, two clamps 14 and two locator bars 16. In this embodiment, the cage former has only a single substantially planar frame 12, and does not include provision for spacer means. Accordingly, and for ease of understanding, the cage former 10 is adapted: {i} to interconnect and locate the cage bars 18a, 18b, 18c and 18d relative to one another, and {ii} to provide two secure junctions suitable as lifting points for the assembled cage.
It will be understood that in alternative embodiments the cage former can comprise two (or perhaps more) substantially planar frames interconnected by linear rods, or by outwardly-flared rods which carry plastic-sleeves such as those of European patent application 0 608 068. The latter of these embodiments would also serve to locate the assembled cage within the pile. The frame could also be of non-planar form, e.g helical. Clearly, many if not all of the available designs of cage former could similarly be utilised with the present invention, or readily be adapted to be utilised with the present invention, if desired.
The cage former 10 is designed for use on a relatively small cage having four cage bars 18, as shown in dotted outline in Fig.1. Two of the cage bars 18a and 18c are securely clamped to the frame 12 by clamps 14, as described in more detail below. The other two cage bars 18b,18d lie alongside the locator bars 16, which bars comprise substantially linear rods to which the cage bars 18a,b are respectively tied by wire ties in known fashion. The locator bars are welded to the frame 12 at 20.
It is understood that two clamps 14 are typically used with a cage, the lifting load being directed to the left or right as drawn in Fig.1, so that the load is shared substantially equally between the clamps 14. The clamps 14 are designed to provide a secure junction between the frame 12 and the cage bars 18a,c, which junctions can act as lifting points for the assembled cage. There may be one pair of clamps for a smaller cage, and perhaps two or more pairs for larger cages. It is of course possible to provide only one clamp, and so only a single lifting point on a particular frame or cage, but this is not in general preferred by those skilled in this art.
The frame 12 comprises a length of bar bent into a number of overlying rings 28 (Figs.2,4). As is not uncommon in single-frame cage formers, the frame comprises at least two complete rings 28, the rings being welded together at spaced locations 22 (Fig.2). One end 24 of the bar can be seen in Fig.1; the other end 26 is shown in dotted outline only. It will be understood that for the small region of overlap of the ends 24,26 the frame 12 comprises three adjacent rings, whilst for the remainder the frame comprises two adjacent rings. Clearly, single-ring frames in which the ends overlap or abut, or frames with three or more complete rings can be used, as desired.
In addition, whilst the frame 12 is substantially circular in plan view, this is not necessary, i.e. a square or substantially square frame could be used with the four cage bars 18 shown. Thus, whilst it is often desirable for the frame or frames to be substantially circular, this is not always the case, and the frame may instead be polygonal to conform closely to the outer periphery of the cage.
The clamps 14 each comprise a body 30, a flap 32, a bolt 34 and a nut 36. As shown in more detail in Fig.2, the body 30 is secured to the side 40 of the frame 12 (rather than to its inside surface 42 as in the prior art document GB 2,310,875). In this way, the cage bars 18a,c can lie against the frame 12 (see Figs. 1 and 4), as do the bars 18b,d, so that the cage bars 18a,c are separated by the maximum distance permitted by the frame 12 (i.e. as the designer intended), and by substantially the same distance as the bars 18b,d.
The body 30 is welded to the frame 12 along the joint line 44 - the line of welding is not shown in Fig.2, but is shown at 46 in Fig.4. In addition, these components are welded together along the joint line facing towards the outside of the frame, i.e. the underside of the paper in Fig.2 - weld line 48 in Fig.4. The body 30 is therefore securely connected to the frame 12, the connection being designed to be sufficient to carry the weight of the entire cage if this is necessary or desired.
In this embodiment, in order to increase the load capacity of the cage former by strengthening the connection between the clamps 14 and the frame 12, connected to the body of each of the clamps 14 are two support members 50, which comprise lugs adapted to engage and overlie a part of the surface 42 of the frame. Notwithstanding that these parts lie within the enclosed volume of the frame 12 they are spaced away from the part of the surface 42 which is engaged by the cage bar 18 in use, i.e. in use the lugs 50 lie to either side of the clamped cage bar 18. The cage bar 18 can lie against the lugs 50 in use, if this is desired.
Fig.4 shows that the weld line 46 continues around the support lugs 50. In this way, the welding between the clamp body 30 and the frame 12 is spread over a larger area, and in particular does not lie in a single plane; accordingly, the clamp 14 is particularly secure, and is not likely to become separated from the frame 12 during rough handling of the cage former or cage on site, for example.
The lugs 50 do not take part in the clamping function, and so are not considered to be a part of the clamping means itself; however, the lugs 50 are beneficial in increasing the strength of the connection between the clamp body 30 and the frame 12, so increasing the load which the cage former 10 can support in use.
The flap 32 is pivotably secured to the body 30 by way of a pivot pin 52, the pivot pin 52 passing through apertures in the bifurcated arms 54 at the end 56 of the flap 32 (Fig.3) as well as aperture 58 adjacent the end 60 of the body 30 (Fig.2). It is desirable that the flap be permanently retained in connection with the body, so that the flap does not become lost in transit or on site. However, in alternative embodiments it is possible that the flap could be secured to the body by a removable pin or nut and bolt assembly, for example.
In an alternative embodiment, the body carries the bifurcated arms, and the flap has a flattened end adapted to lie between the bifurcated arms, the flattened end and bifurcated arms being apertured to receive a pivot pin or the like; such an alternative embodiment reverses the constructions of the ends 56 and 60.
As shown in Fig.3, the end 62 of the arm has an elongated recess 64 and a through-aperture 66. The recess 64 is adapted to receive the T-shaped head (not shown) of the bolt 34, and the aperture 66 to receive the shank of the bolt. When the T-shaped head of the bolt 34 is received in the recess 64 it is not able to rotate about its longitudinal axis, so that the nut 36 may be tightened thereupon without requiring separate means to prevent rotation of the bolt.
There is sufficient freedom between the aperture 66 and the shank of the fitted bolt 34 to permit the bolt to pivot within the plane of the clamping means sufficiently so that the free end of the bolt, and the nut 36 carried thereby, can pass around the end 70 of the body 30.
As shown in Fig.2, the end 70 of the body 30 has a pair of bifurcated arms 72 which can receive therebetween the shank of the bolt 34. The nut 36, when secured to the shank of the bolt 34, can be tightened against the surface of the arms 72 so as to reduce the area enclosed by the body, flap and bolt, and clamp a cage bar 18 located therewithin. The arms 72 terminate in a raised lip 74 which is adapted to prevent the nut sliding out from between the arms 72. Though not shown in the drawings, there can be a washer or washers located between the nut 36 and the arms 72, if desired. The provision of bifurcated arms 72 allows the clamp to be provided complete, i.e. with the nut 36 already located upon the shank of the bolt 34, the user merely having to swing the flap 32 around the cage bar 18, and swing the bolt 34 so that the shank enters between the arms 72. In some embodiments the extreme end of the threads of the shank of the bolt 34 might be deformed so as to prevent the inadvertent removal of the nut therefrom, which serves to ensure that all of the components of the clamp are maintained together until required.
It will be appreciated from the drawings that the provision of the clamping means alongside the frame 12 rather than within it, i.e. outside the area enclosed by the frame 12, results in a cage former 10 in which the orientation of the bolt 34, and the position of the nut 36, can be chosen without any significant encumbrance from the frame 12. Thus, in many cages it is highly desirable for the bolt to project outwardly of the assembled cage, and for the nut(s) to be accessible from outside the cage. It is also desirable that neither the bolt nor the nut project into the cover zone, and the design of the relative lengths and positions of the body, flap and bolt can be chosen to ensure that this will not occur, i.e. be chosen to ensure that the bolt and nut will always lie within the overall projected area of the frame 12. Typically, as shown in Fig. 1, the bolt will project at an acute angle α to the radial direction R, the angle α being predetermined by the designer having prior knowledge of the diameter of the cage bar 18 needing to be clamped.
As shown in Figs. 1 and 4, it is also a feature of the invention that the body 30 does not itself project into the cover zone, i.e. the body 30 does not extend beyond the overall projected area of the frame 12.
As shown in Figs. 1 and 3, the central region 76 of the flap 32 is narrowed. This is partly to save weight, but is predominantly to permit the central region to be of curved or substantially circular cross-section. As shown in Fig.4, the central region of the body also has a curved surface 80. In use, it is the central region 76 of the flap 32, and the surface 80 of the body 30, which engage the cage bar 18. It has been found that a curved surface is more able to locate between adjacent raised transverse ribs which as above described are a typical feature of the cage bars used in pile cages, and so provide a more secure connection therewith. On the contrary, a large-area flat surface would tend to sit upon the ribs, rather than locate between them.
It will also be observed from Fig.4 that the surface 80 of the body 30 is flush with the surface 42 of the frame 12; it is therefore intended that in this embodiment the rings 28 will also lie between the ribs of the cage bar 18. If, however, it is found that the particular arrangement and sizes of the rings 28, and the particular size and spacing of the ribs on the cage bar 18 will cause the ribs of the cage bar 18 to lie upon the surface 42, then the body 30 can be secured to the frame so that its surface 80 stands proud of the surface 42 by a distance substantially equal to the height of the ribs (perhaps by as much as 3 mm), ensuring that the surface 80 can engage the cage bar directly.

Claims

A cage former (10) for use in a pile cage, the cage former including a frame (12) and a clamping means (14) for clamping a cage bar (18) to the frame so as to provide a secure junction between the frame (12) and the cage bar (18a, 18c) the junction being secure enough to act as a lifting point for the pile cage, characterised in that the clamping means (14) lies to the side of the frame (12).
A cage former according to claim 1 in which the clamping means has a body member and one or more support members are connected to the body member, the or each support member overlying a part of the inside surface of the frame which will not be engaged by a cage bar.
A cage former according to claim 2 in which there are two spaced apart support members, and in use a cage bar lies between the support members.
A cage former according to claim 2 in which the clamping means is secured to the frame by welding, the or each support member also being welded to the frame.
A cage former according to claim 1 in which the clamping means comprises a body member (30), a flap member (32), and securement means (34,36).
A cage former according to claim 5 in which the body member is secured to the frame and the flap member is pivotably connected to the body member, in which the securement means comprises a bolt (34) and a nut (36), the flap member having an aperture through which a part of the bolt can pass, the head of the bolt being retained by the flap member, and in which the body member has a bifurcated section which can receive the free end of the bolt and against which the nut can be tightened to reduce the area enclosed by the clamping means.
A cage former according to claim 6 adapted so that in the assembled cage the free end of the bolt projects towards the outside of the cage.
A cage former according to claim 7 in which the free end of the bolt is angled at a acute angle (α) to the radius (R) of the cage.
A cage former according to claim 1 in which at least part of the body member and/or flap member are of curved or substantially circular cross-section.