GB2274299A

GB2274299A - Cage for reinforcing a concrete pile

Info

Publication number: GB2274299A
Application number: GB9300995A
Authority: GB
Inventors: Stephen Render
Original assignee: GRAY PREFABRICATION SERVICES L
Current assignee: GRAY PREFABRICATION SERVICES L
Priority date: 1993-01-16
Filing date: 1993-01-16
Publication date: 1994-07-20
Also published as: DE69405255T2; EP0608068B1; EP0608068A1; GB9300995D0; DE69405255D1

Description

2274299 Title CAGE FOR REINFORCING A CONCRETE PILE.

Field of the invention

The present invention relates to a cage for reinforcing a concrete pile.

Background of the invention

It is known to use, for the purpose of reinforcing a concrete pile, a cage having longitudinally extending bars arranged at the corners of a polygon and secured to transverse rods. These transverse rods act to keep the longitudinal bars apart and to add structural strength to the cage.

It is important that the cage should be correctly located within the concrete so that an adequate thickness of concrete should surround all parts of the cage. In order to achieve this aim, it is known to place plastics spacer wheels on the transverse rods of the cage. These spacers are split wheels that can be pushed onto the transverse rods and they are intended to roll on the walls of the bore into which the cage is lowered to centre the cage within the bore.

It is also known to form a cage by first producing support structures which comprise transverse frames, that may be formed by a rod bent into a circle or a polygon, and longitudinal rods that are secured to the frames to keep the frames at the correct distance apart and in planes that are correctly inclined relative to the longitudinal axis of the cage. To form a cage, two or more such support structures are placed in line with one another and the longitudinal cage bars are positioned on the frames and secured to the support structures.

2 The use of spacer wheels has certain associated disadvantages. In particular, because of the cost of the spacer wheels and the labour involved in mounting them on the cage, they add considerably to the expense. Furthermore, they can be dislodged while the cage is being lowered into the bore, for example if they meet an obstruction or if they received a knock during rough handling of the cage. If this should occur, there is no way of knowing that they have come away and this may lead to cage misalignment. A still further problem is that they can interfere with the flow of concrete in the bore.

Obiect of the invention The invention therefore seeks to provide a support structure that can enable a cage to be constructed in such a manner that its correct alignment in a concrete pile can be ensured without the need for plastics spacers wheels.

Summary of the invention

According to the present invention, there is provided a support structure for use in the production of a cage for reinforcing a concrete pile, the support structure comprising at least two transverse frames and a plurality of metal rods secured to and extending between the transverse frames, wherein at least three of the rods extending between the frames have radially outwardly offset guide portions that lie outside the volume bounded by the frames and are coated with a plastics material.

Preferably one of the two transverse frames is of larger area than the other whereby support structures may be stacked one partly inside during storage and transportation.

The metal rods are preferably evenly distributed about the circumference of the transverse frames, the optimum number of rods being dependent upon the size of the frames.

3 Brief description of the drawings

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

Figure 1 is a side view of a support structure for use in producing a cage, Figure 2 is a side view of a cage produced using two support structures as shown in Figure 1, Figure 3 is an end view of the cage shown in Figure 2, and Figure 4 is a section through an alternative form of plastics sleeve fitted over the guide portions of the metal rods in a further embodiment of the invention.

Detailed description of the drawings

Figure 1 shows a support structure 10 formed of two circular frames or rings 12, 14 connected to one another by four longitudinal metal rods 16. The frames 12, 14 need not be circular and the number of metal rods may be three or more.

Each of the metal rods 16 has a radially outwardly offset guide portion 18 that lies outside the volume bounded by the frames 12, 14. The guide portions 18 are covered with a plastics material 20 which may be a preformed plastics sleeve fitted over the metal rods prior to their being bent to form the cranked portions.

Figure 4 shows an alternative form of sleeve 201 having a flat outer surface, defined by flanges 20a and 20b that extend laterally from both sides of the sleeve.

4 The frame 12 is of smaller diameter than the frame 14 as a result of which the support structure is conically tapered and one can stack several support structures 10 partly one inside the other. The frames 12 and 14 are sized such that the inner diameter of the larger frame exceeds the outer diameter of the smaller frame by an amount corresponding to the diameter of the longitudinal bars 22 secured to the support structures 10 to form the finished cage, as shown in Figure 2.

Figure 2 shows a complete cage formed of two support structures 10 arranged at opposite ends of the cage. Four bars 24 are secured to the support structures 10 and pass inside the larger frames 14 but outside the smaller frames 12 of the structures. This configuration helps to retain the bars 24 in position even prior to the bars being secured in position by ties or welding and makes for a stronger cage.

In the finished cage, the plastics covered guide portions 18 lie outside the volume bounded by the cage bars 24 and act to guide the cage as it is being lowered into a bore and to centre the cage within the bore. These guide portions therefore act in place of spacer wheels but offer the considerable advantage of being integral with the cage so that they cannot be dislodged away while the cage is being lowered into a bore. Furthermore, the cost of a cage incorporating such guide portions is less than a cage fitted with spacer wheels, there being both material and labour savings to be achieved by the construction of the invention.

The above description of a preferred embodiment is given only by way of non-limiting example and various modifications may be made without departing from the scope of the invention as set out in the appended claims.

For example, as the guide portions are used for centring the cage, there need only be three. In larger cages, on the other hand, it may be desirable to use more than four. It is not essential for all the rods of the support structure to include offset guide portions nor is it necessary for the number of longitudinal bars in the cage to match the rods in the support structures.

It will also be clear that when making longer cages, more than two support structures may be needed along the length of the cage and these support structures may taper in same or opposite directions.

6

Claims

1. A support structure for use in the production of a cage for reinforcing a concrete pile, the support structure comprising at least two transverse frames and a plurality of metal rods secured to and extending between the transverse frames, wherein at least three of the rods extending between the frames have radially outwardly offset guide portions that lie outside the volume bounded by the frames and are coated with a plastics material.

2. A support structure as claimed in claim 1, wherein one of the two transverse frames is of larger area than the other whereby support structures may be stacked one partly inside during storage and transportation.

3. A support structure as claimed in claim 1 or 2, wherein the metal rods are evenly distributed about the circumference of the transverse frames.

4. A support structure as claimed in any preceding claim, wherein the plastics material coating on the guide portions are formed as plastics sleeves fitted over the rods.

5. A support structure as claimed in claim 4, wherein the plastics sleeve has a flat outer surface defined by flanges extending laterally from both sides of a cylindrical tube.

6. A support structure constructed, arranged and adapted to operate substantially as herein described with reference to and as illustrated in the accompanying drawings.

7. A cage comprising a plurality of longitudinal bars secured to two or more support structures as claimed in any preceding claim.