GB2433912A

GB2433912A - A concrete keyway former

Info

Publication number: GB2433912A
Application number: GB0519776A
Authority: GB
Inventors: Peter Dew; Marc Clement
Original assignee: Laing Orourke PLC
Current assignee: Laing Orourke PLC
Priority date: 2005-09-28
Filing date: 2005-09-28
Publication date: 2007-07-11
Anticipated expiration: 2025-09-28
Also published as: GB2433912B; GB0519776D0

Abstract

A variable keyway 55 is formed along a longitudinal side of a concrete paving 402 by a controllably movable former 50, 50b of a mould 10, as a paving machine (1) (figure 8 - not shown), carrying the mould 10, is driven over unformed concrete (e.g. for airfield paving). The output of sensors (220, 240) (figure 6 - not shown), which sensors determine the height of paving 402 to be laid at a specified location, and that of the substrate, upon which the paving is to be laid, are used to determine the desired keyway position and size. Sensor 260 measures whether the current keyway position matches the desired one and microcontroller 200 adjusts hydraulic rams to move one or both (60, 80) (figure 5b - not shown) of the keyway former 50.

Description

I

A KEY WAY FORMER

The present invention concerns a keyway former, a paving apparatus and a method of laying a paving slab, and more particularly but not exclusively relates to a keyway former, paving apparatus and method for laying variable thickness airfield paving. The inventions also relates to paving.

Airfield paving is commonly laid by a slip form paving machine, which typically consists of a tracked vehicle fitted with a hydraulically controlled concrete mould. Raw concrete of suitable width and depth is roughly laid onto the substrate to be paved and the slip form paver moves along the desired direction.

A hydraulic mould forms the concrete into the required shape and thickness in a continuous operation.

is A need for thick airfield paving has arisen due to the increase in the physical weight of commercial aircraft. However, with increased thickness comes increased cost. It is known to form variable thickness paving but differential movement as a load moves from one slab to the next can be a significant problem.

It is known to provide a keyway 7 in the longitudinal joints of paving to allow adjacent paving slabs 8, 9 to be interlocked, as shown schematically in Figure 2, thereby minimising any movement when under load conditions. By interlocking the slabs, differential movement is eliminated. Under current practice for laying concrete slabs of a uniform depth, a typical method for producing the keyway in the side of the concrete slab is to fix a suitable rigid former to the side of the concrete mould thereby forming the keyway as the concrete is paved. Such a concrete mould is shown in Figure 3a, and consists essentially of a top plate 11 and side plates I 3a, 1 3b having a fixed size keyway mould. The paving 17 is laid on a substrate 19. This method produces a paving 17 of a uniform thickness with a uniform keyway throughout the paving as shown schematically in Figures 3b and 3c.

However, this practice has drawbacks in that it cannot be used where variable thickness paving is desired. Typically when constructing large areas of concrete paving, many hundreds of metres of paving slab may be laid in a single operation.

With known keyway formers, each change to the former would take a few hours to complete, rendering the use of a keyway economically unviable.

It is an aim of the present invention to alleviate the problems of the prior art and to provide a means of enabling the production of a variable thickness paving having a keyway formed in the longitudinal joint.

According to a first aspect of the present invention, there is provided a keyway former for forming a keyway in a longitudinal side of a concrete paving as the paving is laid by a paving apparatus, comprising a keyway former system which is controllably moveable during motion of the paving apparatus. The keyway former system may comprise an upper forming portion and a lower forming portion.

An advantage of the keyway former of this aspect of the invention is that the dimensions and position of the keyway can be adjusted to correspond to the thickness of the paving being laid, as it is being laid, and the variable thickness paving with non-uniform keyway can be laid within an economical time frame, without having to stop the paving apparatus to make the adjustments. A schematic representation of a side view of such a keyway in variable depth concrete is shown in Figure 4. The substrate 40 is uneven, meaning that the paving 45 laid on it is also uneven in thickness. Consequently, the keyway 55 is also variable in its depth and position.

The moveable keyway former system provides flexibility in the design of paving such as airfield paving. For example, the position of the keyway can be moved to ensure the correct distance from the keyway to the paving upper surface. If a keyway is too near the upper surface, a crack can easily propagate from the surface through to the keyway, and can significantly diminish the paving load bearing capacity. Thus, with a moveable keyway former system, the keyway can be designed to be at a distance far enough below the paving surface to prevent crack propagation. Whilst this is a commonplace consideration in uniform depth paving, it has been a factor in preventing the use of a keyway in variable depth paving.

The design flexibility also allows the user to adapt the keyway design to account for the characteristics and availability of local materials, and to design paving (such as airfield paving) to cope with different loads, such that the impact characteristics of different aircraft using an airfield can be taken into consideration in the paving design.

According to a second aspect of the invention, there is provided a paving apparatus for laying concrete paving on a substrate, comprising a former for forming the paving as it is laid, and a controllable keyway former for forming a keyway in a longitudinal side of the paving during the laying thereof, and a control system, wherein the keyway former is controllably moveable during motion of the paving apparatus.

The keyway former may have upper and lower forming portions. Preferably, the upper forming portion and the lower forming portion are mould portions.

Preferably, one of the upper forming portion and the lower forming portion includes a central straight portion extending between the upper forming portion and the lower forming portion. Preferably, the upper forming portion and/or the lower forming portion are hydraulically controllable, such as by a hydraulic ram attached thereto.

Preferably, the upper forming portion and lower forming portion are controllable independently of each other. This means that only the necessary adjustment at a point in time is to one or other of the forming portions, the process may be highly efficient. It also enables the size of the keyway former to be increased or decreased to the desired size as may be necessary.

According to a third aspect of the present invention, there is provided a control system configured for controlling the moveable keyway former of the first aspect of the invention. Preferably, the control system includes at least one sensor, upon the output of which the movement of the keyway former is based. The sensor may be a paving surface level sensor. The sensor may be a substrate surface level sensor. The sensor may be a keyway position sensor.

According to a fourth aspect of the invention, there is provided a method of laying concrete paving using a paving machine, the paving having a keyway formed in a longitudinal side thereof, the method comprising determining the thickness of paving to be laid at a specified location, determining keyway dimensions and position based on the thickness of the paving to be laid at the location, controllably adjusting the keyway former to desired dimensions and position for the location, and laying the paving with the keyway.

Preferably, the method further comprises the steps of moving the paving machine to a new location, determining the thickness of paving to be laid at the new location, controllably adjusting the keyway former to desired dimensions and position for the new location, and laying the paving with the keyway.

The method advantageously allows a keyway of a non-uniform height, width and position to be incorporated into variable thickness paving as the paving is laid, without needing to stop the paving machine each time a different former configuration is required.

Preferably, the paving thickness is determined using at least one sensor, which may be a paving surface level sensor. The sensor may be a substrate surface level sensor. The sensor may be a keyway position sensor.

According to another aspect of the invention there is provided a paving slab with a keyway having a varying vertical height. According to another aspect of the invention there is provided a paving slab with a keyway having a varying vertical position.

The present invention may be carried out in various ways and an example of a keyway former, paving apparatus, paving and method in accordance with the invention will now be described in the following non-limiting description with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of an embodiment of variable paving thickness airfield paving in accordance with the present invention; Figure 2 is a schematic of a prior art keyway formed in a joint between two concrete paving slabs; Figure 3a is a schematic of a prior art concrete mould having a fixed keyway; Figure 3b is a schematic of a uniform paving with keyway of Figure 3a; Figure 3c is a cross-sectional view through line X-X of Figure 3b; Figure 4 is a more detailed longitudinal section through the paving of Figure 1; Figure 5a is a schematic representation of a concrete mould including keyway formers according to the present invention; for forming the paving shown in Figures 1 and 4; Figure 5b is a more detailed view of one of the keyway formers shown in Figure 5a; Figure 6 is a schematic cross-sectional representation of a control system for controlling the keyway formers of Figure 5a; Figure 7 is an operational flowchart for the keyway formers of Figure 5a Figure 8 shows a slip form paving machine of the type with which the keyway formers of Figure 5a may be used.

A slip form paving machine 1, as typically used for laying concrete paving is shown schematically in Figure 8 and comprises a tracked vehicle having a concrete mould 10 at a lower end thereof. As the paving machine I is driven over unformed concrete, the concrete mould 10 forms the concrete into a paving slab of a desired cross section.

The concrete mould 10, shown schematically in Figure 5a comprises a substantially inverted-U shaped elongate section 11, having an upper mould surface 15 and side plates 20a and 20b which each extend perpendicularly downwards from the ends of upper mould surface 15 to complete the U-shape.

The side plates 20a, 20b may be removably attached to the upper mould surface 15 so as to be adjustable relative thereto.

The upper mould surface 1 5 and side plates 20a, 20b are essentially flat plates in the present embodiment, although they could be curved if desired according to the paving design. Keyway fomers (or former systems) 50, SOb are provided in the region of the side plates 20a and 20b.

Each keyway former 50, SOb comprises (as shown in Figure 5b) an upper mould 60, a lower mould 80 and a central spacer plate 100. The upper mould comprises a formed plate having a straight top portion 62, a dog-legged elongate central portion 64 that is oriented at an angle from and extends away from the top portion 62, and a straight lower portion 66 that extends away from the central portion 64 in a direction parallel to the top portion 62.

The upper mould 60 is formed with rounded corners 61, 63 between the top 62 and central 64 portions, and the central portion 64 and bottom portion 66, such that the upper mould 60 is gently curved. The details of the radii and of the angles between portions of the upper mould are design driven and will be calculable by the person skilled in the art.

The upper mould 60 is attached at the top portion 62 thereof to a hydraulic ram 70 for slidable vertical movement thereof relative to the side plate 20a of the concrete mould 10. As shown in Figure 5b, the top portion 62 rests on the interior wall 22a of side plate 20a such that the central portion 64 and lower portion 66 extend inwardly into the concrete mould 10.

The lower mould 80 is, in the present embodiment, a mirror image of the upper mould 60 and comprises a formed plate having a straight lower portion 82 that curves into a dog-legged central portion 84 that is oriented at an angle from and extends upwards away from the lower portion 82, and a straight top portion 86 that extends upwards away from the central portion in a direction parallel to the lower portion 82.

The lower mould 80 is attached at the lower portion 82 thereof to a hydraulic ram 110 for slidable vertical movement thereof relative to the side plate 20a of the concrete mould 10. As shown in Figure 5b, the lower portion 82 rests on the interior wall 22a of side plate 20a such that the central portion 84 and upper portion 86 extend inwardly into the concrete mould 10.

The central spacer plate 100 comprises an elongate flat plate oriented parallel to the side plate 20a. In a modification, the spacer plate 100 is attached to at one of the upper mould 60 at the lower portion 66 and the lower mould 80 at the upper portion 86, and is aligned with the straight portion 66 or 86 to bridge the gap between the upper mould 60 and the lower mould 80.

In this manner, the keyway former 50 is formed of at least two separate components which can be moved relative to one another to enable the adjustability of the keyway former 50.

An identical keyway former 50b (in a minor image of former 50) is attached to an interior side 22b of side plate 20b via two hydraulic rams 170, 210 (Figure 6) mounted to an external wall 26b of the side plate 20b, such that a keyways 55 can be formed along both longitudinal edges of the paving slab.

The hydraulic rams 70, 110, 170 and 210 are automatically controlled by a central microcontroller 200, shown schematically in Figure 6 as part of an embodiment of a control system for the moveable keyway former 50. The io microcontroller 200 directly controls four separate hydraulic ram controllers 215a, 215b, 215c and 215d, each of which is configured to control one of the hydraulic rams 70, 110, 170 or 210. The central microcontroller 200 instructs each ofthehydraulic ram controllers 215a, 215b, 215c and 215d independently to produce the required vertical movement of the hydraulic rams.

The microcontroller 200 issues instructions to the hydraulic ram controllers based on the output of at least one sensor in the control system. The control system of Figure 6 includes three such sensors: a paving surface sensor 220, a substrate surface sensor 240 and a keyway position sensor 260.

Paving surface sensor 220 senses the level of the paving surface at a particular predetermined location. The substrate surface sensor 240 senses the level of the surface of the substrate upon which the paving is to be laid. The keyway position sensor 260 detects the current positions of the keyways 55.

The control system further includes a user interface 250 such that the user of the paving machine can enter instructions to the control system manually. A display 255 allows the user to monitor salient information during operation of the keyway former. A longitudinal motion sensor 270 monitors the longitudinal position of the paving machine during operation thereof.

As shown in Figure 4 a longitudinal slab of paving 406 in the paving may have variable thickness with a keyway 55 changes in vertical height and vertical depth with the variable thickness. Keyway 55 is lower and thicker at thicker portions 408 of paving slab 406.

The flowchart of Figure 7 shows a sequence for operation of the keyway former 50. In step 300, the paving surface sensor 220 determines the height of paving to be laid at a particular longitudinal location. The substrate surface sensor 240 then at step 302 determines the height of the substrate upon which the paving is to be laid. The output of theses sensors is used at step 304 to calculate or otherwise determine the desired optimum keyway position and size. The keyway position sensor 260 measures whether the current keyway position matches the desired position, and the microcontroller 200 adjusts (at step 306) the hydraulic rams accordingly to move one or both moulds 60, 80 of the keyway formers 50. The paving machine I is then driven forwards (at step 308) -of course such motion maybe continuous. As it does so, the unformed concrete in front of the paving machine 1 is squeezed through the concrete mould 10 including the keyway former 50, to be formed into a paving slab with a keyway. The control system again (at step 310) monitors the output of sensors 220, 240 and 260 to determine whether the keyway former requires adjustment before the next length of paving is to be laid. The former 50b may be simultaneously controlled in a similar manner by the controller 200.

It is anticipated that during movement of the keyway former between longitudinal sections of paving may cause the mould members 60 and or 80 to tilt, which could produce a discontinuity in the profile of the completed keyway. Discontinuities are undesirable, so as to avoid jamming between adjacent paving slabs as the concrete expands and contracts during its operational lifetime. In a preferred embodiment, the control system software includes a compensation mechanism to take this into account. In addition, or alternatively, the mould members 60 and 80 could be formed in two sections (split longitudinally) rather than a single section to minimise the tilt effect.

In practice, individual parallel paving slabs 406 may be formed, each with two keyways 55 and spaced apart from one another. In a separate longitudinal run later on, the space between the slats 406 may be filled with similar paving/concrete.

It is further envisaged that the depth of the keyway is variable in the direction of the arrow 500 shown in Figure 5b. This could be achieved using one or more further hydraulic cylinders 550 as shown schematically in Figure Sb.

Upper and lower mould members 60 and 80 could be formed telescopically in more two or more portions allowing the movement of the portions that are attached to the hydraulic cylinder.

Figures 1 and 4 show that an airport terminal 400 paving 402 may be formed with areas 3 outside parking bays 5 for aircraft 404 which are thinner than in bays 5 thereby saving on cost of paving while having paving which is thick enough where the aircraft move/park. As shown in Figure 4 a longitudinal slab of paving 406 in the paving may have a variable thickness with a keyway which changes in vertical height and vertical depth with the variable thickness. Keyway 55 is lower and thicker at thicker portions 408 of paving slab 406.

It will be apparent to the skilled person that the invention is not limited to the specific embodiments described above and that other embodiments are possible whilst meeting the requirements of the accompanying claims.

Claims

CLAIMS

I. A keyway former for forming a keyway along a longitudinal side of a concrete paving as the paving is laid by a paving apparatus, the keyway former comprising a keyway former system which is arranged to be controllably moveable during motion of the paving apparatus for forming a variable keyway.

2. A paving apparatus for laying concrete paving, comprising a former for forming the paving as it is laid, and a controllable keyway former for forming a keyway in a longitudinal side of the paving during the laying thereof, wherein the keyway former is arranged to be controllably moveable during motion of the paving apparatus.

3. Apparatus as claimed in claim I or claim 2 in which upper and lower forming portions are provided as mould portions.

4. A keyway former as claimed in claim 3 in which one of the upper forming portion and the lower forming portion includes a central straight portion extending between the upper forming portion and the lower forming portion.

5. A keyway former as claimed in claim 3 or claim 4 in which the upper forming portion is hydraulically controllable.

6. A keyway former as claimed in claim 3 or claim 4 or claim 5in which the lower forming portion is hydraulically controllable.

7. A keyway former as claimed in any one of claims 3 to 6 in which the upper forming portion and lower forming portion are controllable independently of each other.

8. A keyway former as claimed in any of claims Ito 7 in which the vertical position of the keyway is variable.

9. A keyway former as claimed in any of claims 1 to 8 in which the vertical depth of the keyway former is variable.

10. A keyway former as claimed in any of claims I to 9 in which the horizontal depth of the keyway is variable.

11. A control system configured for controlling a moveable keyway former as claimed in any of claims 1-10.

12. A control system for controlling a moveable keyway former for a slip forming apparatus, the control system having a controller connected by a signal path is arranged to connect to a keyway former for controlling the keyway former in response to a signal received at the controller from at least one sensor.

13. A control system as claimed in claim 11 or claim 12 including a hydraulic ram removably attached to which the keyway former.

14. A control system as claimed in claim 11, including at least one sensor, the sensor being arranged to provide a signal to a controller, the controller being arranged to controller movement of the keyway former.

15. A control system as claimed in claim 12 or claim 14 in which at least one sensor includes a paving surface level sensor.

16. A control system as claimed in claim 14 in which the sensor is a substrate surface level sensor.

17. A control system as claimed in claim 14 in which at least one sensor includes a keyway position sensor.

18. A method of laying concrete paving using a paving machine, the paving having a keyway formed in a longitudinal side thereof, the method comprising determining the thickness of paving to be laid at a specified location, determining keyway dimensions and position based on the thickness of the paving to be laid at the location, controllably adjusting a keyway former to desired dimensions and position for the location, and laying the paving with the keyway.

19. A method as claimed in claim 18, further comprising the steps of moving the paving machine to a new location, determining the thickness of paving to be laid at the new location, controllably adjusting the keyway former to the desired dimensions and position for the new location, and laying the paving with the keyway.

20. A method as claimed in claim 18 or claim 19 wherein the paving thickness is determined using at least one sensor.

21. A method as claimed in claim 20 wherein the at least one sensor includes a paving surface level sensor.

22. A method as claimed in claim 20 or claim 21 wherein the at least one sensor includes is a substrate surface level sensor.

23. A method as claimed in claim 20 or claim 21 or 22 wherein, the at least one sensor includes a keyway position sensor.

24. A method as claimed in claim 18 or claim 19 wherein the keyway former is hydraulically adjusted by a controller.

25. A concrete paving comprising a keyway formed in a longitudinal side thereof formed by a moveable keyway former according to any of claims 1-10.

26. A concrete paving comprising a keyway formed according to the method of any of claims 18 to 25.

27. A paving slab with a keyway having a vertical position which varies along a longitudinal direction of the slab.

28. A paving slab with a keyway having a vertical depth which varies along a longitudinal direction of the slab.

29. A paving slab with a keyway having a horizontal depth which varies along a longitudinal direction of the slab.

30. A keyway former substantially as described herein and in the accompanying drawings.

31. A paving apparatus substantially as described herein and in the accompanying drawings.

32. A method substantially as described herein and in the accompanying drawings.

33. Paving substantially as described herein with reference to Figures 1 and 4 of the accompanying drawings.