GB2543795A

GB2543795A - Manufacture of pre-stressed concrete members

Info

Publication number: GB2543795A
Application number: GB1519053.1A
Authority: GB
Inventors: Hamilton Jardine Mark
Original assignee: Poundfield Products Ltd
Current assignee: Poundfield Products Ltd
Priority date: 2015-10-28
Filing date: 2015-10-28
Publication date: 2017-05-03
Anticipated expiration: 2035-10-28
Also published as: GB201519053D0; GB2543795B

Abstract

A concrete cutting apparatus and associated method with a transport bed 12`, 12`` of a set of elongate tracks 20 linked to a motor system (18, figure 7) that drives them. There is a measurement system (70, figure 7) for determining the size of the cut concrete members and a restraining and braking 38, 24 system for holding the concrete members whilst being cut by the transverse saw (14, figure 6). The tracks each have linear bearings or rollers 40 and conveyors (30`, 30``, figure 4) to enable longitudinal motion. The transport bed may be formed of two portions (12`, 12``) each with their own conveyors and the braking members are positioned near to the second portion. There may be a clamping system (60, figure 4) configured to operate with the first portion of the transport bed. The conveyors may comprise a pair of drive chains (26, figure 4) coupled with a plurality of beams 28. There may be a control system (80, figure 7) which may be connected to the measurement system, motor system or restraining system. The measurement system may utilise LIDAR sensors.

Description

Manufacture of Pre-stressed Concrete Members

BACKGROUND a. Field of the Invention

The present invention relates to the field of manufacture of a plurality of prestressed elongate concrete members having desired lengths, and specifically concerns an apparatus and a method for manufacturing a plurality of elongate prestressed concrete members having individual desired lengths. b. Related Art

One way of providing a solid floor in commercial or residential buildings is to use elongate pre-cast and reinforced concrete beams, which span a void between opposite walls or across a gap between sections of foundation. The beams are cast in a mould, the length of which is adjusted to produce a beam having the desired length, which is just sufficiently long for its ends to rest securely on the wall or foundation but not so long as to overlap the wall or protrude into gaps such as those inside a cavity wall which must be left clear. Such beams are commonly used for the ground floor, but may also be used for the first floor or higher upper floors.

The beams are formed from prestressed concrete, in which each beam usually comprises between 3 to 5 tendons, generally high tensile steel cables or wires, to strengthen the concrete against the tensile stress experienced when the beam carries a load. Floor beams for domestic dwellings may be about 125 mm to 175 mm tall and about 100 mm to 150 mm wide. Such beams span an average length of about 4 m to 6 m, and can span lengths up to 7 m. Beams of greater depth and width can, of course, span greater distances. It is common for concrete floor beams to have substantially T-shaped profiles, such that each block is aligned adjacently parallel to another block with the T-shaped profile being inverted so that the broad face of the beam is lowermost. Filler may then be poured into the given spaces to seal the concrete blocks together in order to provide flat flooring.

Building designs can have any desired horizontal dimensions for the span between the foundations or internal walls, and so each floor beam must have the correct length that is tailored to the particular design of the building. Floor beams are the most common type of concrete member within the structural frame of the building that requires bespoke dimensions. Other examples of pre-stressed elongate concrete members that will, in general need to be manufactured to a specific length are hollow core flooring slabs, concrete I-beams, lintels, support posts or wall panels.

In the case of floor beams intra-wall cavities must be left free of any obstruction at the ends of the beams when setting the floor beams in place. It is therefore essential for the beams to be cast with precision and accuracy in order to ensure that the beams do not extend into wall cavities. Generally, this means that the beams have to be cast with a total tolerance in the desired length of between about 2 mm to 5 mm.

Methods for producing such bespoke beams include moulding the concrete beams to specific shapes and lengths. A range of differently sized and shaped moulds are used as required in the production process. However, for a business providing tailored concrete floor beams, this means that a new mould is needed for each new length order, which is not necessarily the most efficient method of production. Additionally, beams which are produced in batches of sizes (for example, a first batch having beams with 5 m lengths and a second batch having 5.5 m length beams) have to be stacked and stored. A batch of beams can weigh around 6 tonnes. Given the size of the beams and the inconvenience of storing and moving beams once cast, it is not feasible to manufacture and store on site cast concrete members having every length which a customer may order, so that such beams can be delivered from stock. This is particularly the case because transport costs for such products become significant over 50 km and so it is not economic to supply a national market from one manufacturing site or a central depository. Therefore, pre-cast beams have to be manufactured to order.

An example of the equipment conventionally used to cast pre-stressed concrete beams to order is shown in Figures 1, 2 and 3 of the attached drawings. In this known apparatus, two side-by-side beds 1 are used to produce pre-stressed concrete floor beams. Each bed 1 bed has 15 parallel steel troughs 2, each of which is 60 m long. The beds may, however, be longer, for example up to 100 m long.

Before concrete is poured, each trough is subdivided along its length by inserting rubber dividers 5 into each trough. The dividers laterally span the trough and therefore have the same cross-sectional shape as the beams cast from the trough. Depending on the lengths of the beams, each bed can therefore cast up to about 225 concrete beams at a time, assuming an average beam length of 4 m. The floor beams cast in the troughs have the same generally T-shaped outer cross-sectional shape as the dividers, in this example being about 150 mm tall, about 127 mm wide at the widest end and about 80 mm wide at the narrowest end. Inside the beams are three steel reinforcing wires 3.

There are a number of problems in the use of such troughs to manufacture beams having many different desired lengths. Firstly, the lengths of steel reinforcing wire 3 that are laid out in the troughs of each bed are stressed up to 70% of their tensile limit. As a health and safety measure, before this is tensioning done the troughs 2 and wires 3 are transversely overlaid with chains 4, which can help to restrain a wire if it should snap. Working in the vicinity of such tensioned wires is, nevertheless, potentially dangerous as it is never possible to be completely sure that there is no defect in a wire which might cause the wire to snap.

It is only after the wires 3 has been tensioned that rubber dividers 5 can be set at appropriate intervals along the troughs to subdivide the trough into segments having a desired length. The dividers have a profile which matches the transverse profile of the interior of each trough. Each divider has for each wire 3 a slot 6 so that the wires slot through each divider once set.

Once set, the dividers, together with the opposite ends of the trough, therefore define the ends of each concrete beam or member to be cast along the length of each trough. It is therefore necessary to set the dividers accurately in place. In practice, this is difficult to do reliably, because the dividers are set in place by a worker walking on top of the bed and manually hammering the each divider into place, after having measured with a tape measure the distance from the trough end or a previously set divider. While doing this, great care must be taken not to drop the hammer onto the tensioned wires 3, as this could cause a wire to snap. The setting of dividers can take up to half a day.

After the dividers have been set, a release agent (not shown) is sprayed on the interior surfaces of the troughs. Finally, steel lifting loops 7, having an inverted U-shape (see Figure 5) are set in place at intervals along each trough so that the cast members can be lifted out of each trough by a crane (not shown) once the concrete has cured.

Once the dividers 5 and lifting loops 7 have been set, concrete is poured over the wires 3, into each trough 2 and left to dry to form a set of elongate pre-stressed reinforced beams or members. The presence of the chains 4, dividers 5 and lifting loops 7 inhibits the flow of concrete along the trough and makes it more difficult to achieve a level top surface for the poured concrete. Generally, as concrete is being poured a worker moves across the bed helping to distribute and level the wet concrete.

After the concrete has set, up to about 360 dividers have to be removed from between the segments. These dividers and then have to be manually cleaned of residual concrete before these can be reused. The segments are, however, still connected by the wires, which then have to be manually cut using an oxy acetylene torch. Only then can the segments be lifted from the troughs and stacked. Rough ends of the cut wires protruding from the ends of each beam then have to be manually reduced with an angle grinder. All of this work is time consuming and inconvenient.

Each bed can only be cast after sufficient orders have been received to fill a complete bed. It is, in general, necessary to aggregate several orders, typically from different customers for different building projects, when casting a full bed. As each concrete member has a tolerance on the desired length of between 2 mm to 5 mm, and a length of typically between 2 m and 7 m, it will almost never be the case that the final length in each 100 m long bed will match a desired length. To minimise wastage at the ends of each cast beam it is, in general, necessary to split up beam segments for each order or customer across the extent of the bed. Then, after the concrete members have all been cast and lifted from the troughs, it is necessary to identify and sort all of the cast members in order to aggregate those destined for a particular order or customer, prior to shipping.

Using the above process, it usually takes six weeks from the point of receiving an order before the concrete members can be manufactured and shipped. In some cases, this process may not be fast enough. For other orders, placed well in advance, it may be necessary to manufacture the concrete members sooner than would be ideal. Construction sites generally do not have storage space for such bulky and heavy members, and so finished concrete members may then have to be stored at the manufacturing site for a time before delivery can be made to the customer at the construction site.

All of this is inconvenient, either for the manufacturer or the customer, and therefore adds to the cost of the finished product.

It is an object of the present invention to provide a more convenient apparatus and method for manufacturing a plurality of elongate pre-stressed concrete members having individual desired lengths.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a concrete cutting apparatus for sequentially cutting from each one of a plurality of elongate prestressed concrete members a plurality of cut segments, each cut segment having a desired predetermined length, the apparatus comprising: a transport bed, the transport bed comprising a set of elongate tracks, said tracks each extending in a longitudinal direction and being laterally adjacent to one another and each track, in use, supporting a corresponding one of said members in a side-by-side configuration prior to cutting of each cut segment; a motor drive system, the set of tracks being linked to the motor drive system such that the motor drive system, in use, drives longitudinal movement of the set of tracks, whereby each of said tracks longitudinally transports said corresponding member towards a desired longitudinal position prior to cutting of each cut segment; a distance measurement system, the distance measurement system being configured to measure for said members a longitudinal position of each of said members transported by said tracks; a restraining system, the restraining system being operable to restrain each of said members in the desired longitudinal position; and a saw, the saw being configured to cut along a transversely extending cutting line through said supported members when longitudinally restrained at said desired longitudinal positions, whereby, in use, said desired predetermined lengths of said cut segments are obtained during cutting by the saw; wherein the restraining system comprises a plurality of brake members, one for each of said members supported on said tracks, said brake members being independently operable to restrain each corresponding member in the desired longitudinal position; the transport bed comprises at least one conveyor, each track being linked to the motor drive system by said conveyor whereby said tracks are, in use, driven by said motor drive system through said conveyor, said conveyor being configured to move said tracks in unison as said members are transported towards said desired longitudinal positions; and each track comprises along its length at least one linear bearing on which said members are supported, each of said bearings permitting relative longitudinal movement between the corresponding supported member and said conveyor whereby, in use, said conveyor imparts said longitudinal movement to each of said members through each linear bearing as said members are transported towards said desired longitudinal positions until the corresponding brake member is used to restrain said member in the desired longitudinal position following which the corresponding linear bearing isolates said restrained member from said conveyor and thus does not impart of any further longitudinal movement to said restrained member.

According to the a second aspect of the invention, there is provided a method of sequentially cutting from each one of a plurality of elongate pre-stressed concrete members a plurality of cut segments of desired predetermined lengths using a concrete cutting apparatus, the apparatus comprising a transport bed, the transport bed comprising a set of side-by-side tracks and a motor drive system, a distance measurement system, a restraining system, and a saw, the method comprising the steps of: i) loading a plurality of said concrete members onto the tracks, whereby the concrete members are supported side-by-side on the tracks; ii) using the motor drive system to drive longitudinal movement of the tracks, whereby each of the tracks longitudinally transports a corresponding concrete member towards a desired longitudinal position; iii) using the distance measurement system to measure for the concrete members a longitudinal position of each of the concrete members transported by the tracks; iv) using the restraining system to restrain each of the concrete members in the desired longitudinal position; and v) when each of the concrete members is restrained by the restraining system in the desired longitudinal position, using the saw to cut along a transversely extending cutting line through the concrete members, whereby, said desired predetermined lengths of said cut segments are obtained during cutting by the saw; wherein the restraining system comprises a plurality of independently operable brake members, one for each of the concrete members supported on the tracks and the transport bed comprises at least one conveyor, each track being linked to the motor drive system by said conveyor and each track comprises along its length at least one linear bearing on which the concrete members are supported, each of said bearings permitting relative longitudinal movement between the corresponding supported member and said conveyor, the method further comprising in step ii) using the motor drive system to move said tracks in unison, said conveyor imparting said longitudinal movement to each of said unconstrained members through each linear bearing as said members are transported towards said desired longitudinal positions until in step iv) the corresponding brake member is used to restrain a corresponding concrete member in the desired longitudinal position following which the corresponding linear bearing isolates said restrained concrete member from said conveyor and thus does not impart of any further longitudinal movement to said restrained member as the motor drive system moves the tracks in unison and unconstrained members continue to be transported towards said desired longitudinal positions until all of the concrete members have been restrained in corresponding desired longitudinal positions by corresponding brake members.

According to a third aspect of the invention, there is provided a method of manufacturing a plurality of elongate pre-stressed concrete members each having a predetermined desired length, the method comprising the steps of: i) setting at least one tensioned tendon into each of at least two casting troughs, said troughs each having opposite ends; ii) pouring concrete into the troughs, and allowing the concrete to set around said tendons to form a plurality of elongate pre-stressed concrete members each concrete member extending between the opposite ends of the corresponding casting trough; iii) removing the concrete members from said troughs; and iv) sequentially cutting from each one of said plurality of elongate pre-stressed concrete members a plurality of cut segments having said predetermined desired lengths using the method according to the second aspect of the invention.

The set of tracks will have at least two side-by-side tracks.

The tracks are preferably substantially parallel with other.

The transport bed may extend just on one side of the cutting line for feeding towards and across the cutting line the portions of the pre-stressed concrete members to be cut into the segments. However, in a preferred embodiment of the invention the transport bed comprises a first portion and a second portion, these portions extending longitudinally away from each other on opposite sides of the cutting line and thereby providing corresponding first and second portions of each of the tracks. In this case, the first and second portions of each track have corresponding first and second conveyors.

The loaded concrete members are then supported by the first portion of the tracks. After cutting, the cut segments are then supported by the second portion of the tracks.

In a preferred embodiment of the invention, the first portion of each track is longer than the second portion of each track, the first portion therefore being adapted to receive the concrete members prior to cutting by the saw, and the second portion being adapted to support the segment cut from the concrete member.

The first and second portions of the transport bed preferably extend at right angles away from opposite sides of said cutting line.

The motor drive system is preferably configured to move all the tracks in unison in either longitudinal direction, for example forwards from the first track portion to the second track portion or backwards from the second track portion to the first track portion, as the position of the concrete members is adjusted relative to the desired longitudinal position.

The brake members may be proximate the second portion of the transport bed, whereby the brake members are configured to restrain the concrete members supported by the second portions of the tracks during cutting of the members by the saw.

The apparatus may further comprise a clamping system that is proximate the first portion of the transport bed. The clamping system may then be configured to restrain the concrete members supported by the first portion of the tracks during cutting of the concrete members by the saw.

The clamping system and the restraining system are therefore provided on opposite sides of the cutting line.

Then, after all of the concrete members have been restrained by the corresponding brake members on one side of the cutting line, the clamping system may be used on the opposite side of the cutting line to further restrain each of the concrete members.

As the motor drive system moves all the tracks of the set of tracks in unison, the motor drive system may have just a single drive motor. After cutting, the cut segments can then be moved all at the same time away from the cutting line by moving all the tracks in unison while continuing to engage the clamping system to restrain the remainder of each concrete member still supported by the first portion of the tracks.

However, in a preferred embodiment of the invention, the motor drive system comprises a first drive motor and a second drive motor. The first portions of the tracks are then linked to the first drive motor by the first conveyor and the second portions of the tracks are then linked to the second drive motor by the second conveyor.

It is then preferred if both the first drive motor and second drive motor are used to independently drive the corresponding track portions.

As the concrete members are then moved into the desired positions, the tracks in both first and second portions may be moved in unison, for example by running the first drive motor and second drive motor at the same effective speed. After the segments are cut just the second drive motor may be used to move the cut segments away from the cutting line for subsequent unloading the cut segments from the second portions of the tracks.

Regardless the number of drive motors, it is preferred that the motor drive system is used to maintain all of the supporting tracks stationary during the operation of each of the independently operable brakes. This gives time for each brake to engage fully while the corresponding concrete member is stationary at the desired position.

The linear bearing may comprise a plurality of rollers that are spaced longitudinally apart along each track. Each roller may be free to rotate in response to a difference in longitudinal speed between the, or each, conveyor and the restrained member.

The rollers for those concrete members restrained by the corresponding brake will therefore rotate if the tracks continue to be moved in unison and thus isolate the restrained concrete member from any further longitudinal movement of the tracks.

The transport bed will, in most cases, be elongate, with a length extending in the longitudinal direction of parallel tracks, and a width extending in a direction transverse to the longitudinal direction. In general the length will be greater than the width, but this will, of course, depend on the length of the cast concrete members to be cut into segments, and the number and spacing of parallel tracks. Most preferably, the tracks are linked mechanically together so that the tracks always move in unison.

The conveyor may comprises a pair of drive chains and a plurality of beams, the chains each extending in a longitudinal direction around an endless loop in a substantially vertical plane proximate opposite lateral sides of the transport bed. The beams may extend in a lateral direction so that the chains are connected together by the beams, whereby the chains are configured to move the laterally extending beams in a longitudinal direction as the conveyor is driven by the motor drive system.

The motor drive system may be configured to engage with at least one of the chains, for example by means of a rotatable shaft with a pair of similar sprockets fixed at opposite ends, whereby the chain, in use, is moved around its loop.

In a preferred embodiment of the invention, the rollers for adjacent tracks are spaced laterally apart along the beams, whereby, in use, the rollers are moved in unison as both chains are driven around their loops by the motor drive system.

Each roller preferably has at least one flange, the flanges of the rollers being spaced longitudinally apart along the length of each corresponding track to provide transverse alignment of the concrete members supported on the tracks.

The concrete cutting apparatus may further comprise a control system that is operatively connected to the distance measurement system and the motor drive system. The control system may be configured to compare for each of the concrete members the measured longitudinal position with the desired longitudinal position and to use the motor drive system to longitudinally move the corresponding tracks on which each of the members is supported until the measured longitudinal position corresponds with the desired longitudinal position.

The control system may be operatively connected to the restraining system, in which case the control system is configured to operate the restraining system to longitudinally restrain each of the concrete members when at the desired longitudinal position.

The control system may then be configured to operate the brake members independently one from another to restrain each corresponding concrete member in the desired longitudinal position.

Preferably, control system is configured to control the first drive motor and the second drive motor independently from each other. The second portion of each track may then, in use, when driven by the second drive motor system longitudinally transport a corresponding cut segment away from the cutting line.

The control system may be configured to use the motor drive system to drive the both the first and second portions of the tracks in unison until the brakes have restrained all of the concrete members in the desired longitudinal positions.

Each of the elongate concrete members prior to the cutting of each cut segment will, in general, extend between opposite first and second ends of the member. The distance measurement system may then be configured to measure for the members a longitudinal position of the first end of each of the concrete members. The cutting of the member then creates a new first end, with the length of the cut segment extending between the old first end and a new end, formed by the cut through the member.

Therefore, each of the segments to be cut from the concrete members extends from the original first end to the cutting line.

The distance measurement system preferably comprises a plurality of lidar (i.e. Light Detection And Ranging) sensors, each sensor being configured to measure a separation from the first end of a corresponding member to the sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a perspective view of an example of the equipment conventionally used to cast pre-stressed concrete members, for example floor beams, in which two side-by-side beds each have a plurality of parallel steel troughs along which steel tendons have been stretched prior to pouring of concrete;

Figure 2 is a side view of a divider according to the prior art, such dividers when inserted at intervals along each of the troughs of Figure 1 prior to pouring of concrete thereby subdividing the trough into sections so that the concrete sets to form segments of predetermined desired lengths;

Figure 3 is a side view of the trough divider, taken along line Ill-Ill of Figure 2;

Figure 4 is a perspective view of part of a concrete cutting apparatus for sequentially cutting from each one of a plurality of elongate pre-stressed concrete members a plurality of cut segments of predetermined desired length, showing concrete members on a first conveyor being transported by moving tracks towards a cutting line of a saw and a second conveyor on the other side of the cutting line;

Figure 5 is a perspective view of part of the concrete cutting apparatus of Figure 4, showing how, as each concrete member is restrained at a desired longitudinal position by individual brake members, free-wheeling rollers on the conveyors beneath those restrained members rotate to cancel the motion of the conveyors, while the conveyors continue to transport the unrestrained members to individual desired longitudinal positions;

Figure 6 is a perspective view of part of the concrete cutting apparatus of Figure 4, showing how, after each of the concrete members is restrained by individual brake members on one side of a cutting line, a clamping system is used to restrain all the concrete members on the other side of the cutting line;

Figures 7 to 9 show schematically how the concrete cutting apparatus of Figure 1 transports a first concrete member to a first desired position at which the member is then restrained by a first brake member;

Figures 10 and 11 follow on from Figure 9, and show how a second concrete member is transported to a second desired position at which the member is then restrained by a second brake member;

Figure 12 follows on from Figure 11, and shows how a third concrete member when transported to a third desired position is restrained by a third brake member;

Figure 13 follows on from Figure 12, and shows how the clamping system is used to restrain all the concrete members on the first conveyor after all the concrete members have been restrained by individual brake members on the second conveyor;

Figures 14 and 15 follow on from Figure 13 and show how the saw is used to cut through all the restrained concrete members along the cutting line; and

Figure 16 and 17 follow on from Figure 15, and show how the brake members are released so that the elongate cut segments of concrete members can be moved away from the cutting line for offloading from the second conveyor and also how the clamping system can then be released.

DETAILED DESCRIPTION

The prior art system of Figures 1 to 3 comprises one or more beds 1 for casting individual elongate concrete members from elongate troughs 2, subdivided by dividers 5, as described in the Background section above.

The invention uses a concrete member cutting apparatus 100, as shown in Figures 4 to 17, to avoid the need to subdivide the casting troughs 2 when casting elongate, pre-stressed concrete members. Cast concrete members 10 are then cast, preferably along the full length of the beds 1, although a terminal divider 5 could be used in one or more troughs, either to subdivide the bed into two or more shorter lengths or with concrete poured just on one side of the divider, if it were desired to cast beams of less than full length.

After the elongate, pre-stressed concrete members 10 are cast as a single length in the troughs 2 of Figure 1, the members are lifted out of the troughs using the steel wire lifting loops 3 cast into each member at points along the length of each member by a crane or other suitable lifting equipment (not shown).

The freshly cast members 10 may be stacked and stored for later cutting, or directly moved and loaded onto concrete member cutting apparatus 100 for cutting to desired lengths. Part of the concrete member cutting apparatus is illustrated in detail in Figures 4 to 6. The operation of the apparatus is shown more completely in the schematic drawings of Figures 7 to 17. In this process, elongate prestressed concrete segments 90 are cut from a plurality of the cast members, each of the cut segments having a predetermined desired length. The plurality of cast members 10 are supported on a transport bed 12. The transport bed 12 has a plurality of parallel tracks 20 which extend in a longitudinal direction and orient the concrete members 10 in parallel with each other in a transverse, or side-by-side, orientation, so that all the cuts can be made at the same time by a saw 14 which slices transversely along a cutting line 16 through the supported concrete members.

In this example, the saw 14 is a circular saw mounted on a carriage 15 that is operable to drop and raise the saw relative to the concrete members and to move the saw transversely along the cutting line 16 when segments 90 are to be cut from the concrete members 10.

In this example there are eleven concrete members 10, which in Figure 5 are labelled individually as 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, and 111. The concrete members are individually supported on eleven corresponding tracks 20, which in Figure 5 are labelled individually as 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, and 211. The invention may, however, be used to cut at the same time (i.e. in the same cutting process step) any number of side-by-side concrete members greater than one. Similarly, the invention may employ any number of tracks greater than one. It is not necessary that all tracks are used or filled and so there may be intervening or laterally outermost tracks that are unfilled. Therefore, as will be appreciated from the following description, it is not necessary for the concrete members to be directly adjacent each other, as the members could be well spaced apart, for example separate by empty tracks.

As shown in Figures 14 to 17, the cutting process leaves behind a remainder of each of the original cast members, which are then shortened elongate concrete members 10’. The process may be repeated so that subsequent segments are cut from the shortened members 10’, until all the original cast members have been segmented into the desired lengths. Typically, there will be a final reminder left (not shown) which is wastage. The pattern of cutting is ideally chosen so as to make the most use of the original lengths of the cast members, with the minimum of wastage.

In addition to the transport bed 12 and saw 14, the concrete cutting apparatus 100 comprises a motor drive system 18, a restraining system 50 and a distance measurement system 70.

As seen most clearly in Figure 4, the transport bed 12 has a first portion 12’ and a second portion 12”, these portions extending longitudinally away from each other on opposite sides of the cutting line 16. As indicated schematically in Figures 7 and 8, the first and second portions 12’, 12” of the transport bed 12 provide corresponding first and second portions of the tracks 20’, 20”. The first portion of the tracks 20’ is sufficiently long to accept the full length of each deposited concrete member 101-111, and the second portion of the tracks 20” is sufficiently long to accommodate each segment to be cut from the concrete members. In order to be cut into segments 90 of desired length, each concrete member has to be moved 25 in a forwards direction of the tracks until the desired length of concrete member is on one or the other side of the cutting line. In this example, this desired length is on the side of the cutting line having the second portion of the tracks 20”, and so cut segments 90 are then offloaded from the second portion of the tracks however, this could, in principle, be reversed, if segments of cut members were then offloaded from the first portion of the tracks 20’.

This motor drive system 18 will, in general, comprise at least one drive motor, and in this example there are two electric drive motors, a first drive motor 18’ for driving the movement of the first portion of the tracks 20’ and a second drive motor 18” for driving the second portion of the tracks 20”. Each set of tracks is therefore linked to the motor drive system such that the motor drive system, in use, drives longitudinal movement of each set of tracks, whereby each of the tracks longitudinally transports a corresponding concrete member towards a desired longitudinal position prior to cutting of each cut segment.

In this example, the linkage is provided by a two pairs of endless drive chains 26’, 26”, one pair for each of the first and second track portions 20’, 20”, and a plurality of a plurality of beams 28, opposite ends 32’, 32” of which are fixed to one or the other of the drive chains in each pair 26’, 26”. The tracks 20 are supported on the beams and are may therefore be moved in either longitudinal direction when the corresponding drive motor 18’, 18” moves each pair of drive chains one way or the other around its loop.

Each drive chain extends in the longitudinal direction around an endless loop in a substantially vertical plane proximate opposite lateral sides 34’, 34” of the transport bed 12 defined by the laterally opposite edges of the outermost tracks 201,211. The beams 28 therefore extend in a lateral direction such that the chains 26’, 26” are connected together by the beams whereby the chains are configured to move the beams in a longitudinal direction in the manner of a conveyor driven by the motor drive system.

The drive chains and beams therefore provide a conveyor 30 for the transport bed 12. The transport bed first portion 12’ contains a first portion 30’ of the conveyor and the transport bed second portion 12” contains a second portion 30” of the conveyor. The tracks 20 are then moved by the motor drive system 18 as this drives the conveyor 30. As each of the concrete members 10 is moved to the corresponding desired longitudinal position, the first and second portions of the conveyor 30’, 30” move the first and second track portions 12’, 12” in unison.

The first and second portions of the conveyor 30’, 30” need not always move in unison, and therefore the corresponding drive motors 18’, 18” are individually controllable by the motor drive system 18. For example, after loading of the concrete members 10 onto the transport bed first portion 30’, the conveyor first portion 30’ may move the track first portion 20’ to transport each concrete member towards the cutting line 16. After the concrete members cross the cutting line, then the conveyor second portion 30” may move the track second portion 20” to assist in transporting each of the concrete members towards the correct final longitudinal position prior to cutting. The person skilled in the art will, however, appreciate from the following description, which explains how each track comprises a plurality of free-wheeling rollers 36, that the movement of the first conveyor portion 30’ alone may be sufficient to move the concrete members in both track portions 20’, 20” even when the second track portion is not driven by the second drive motor 18”.

After cutting of the segments 90 from the concrete members, the second drive motor 18” is activated while the first drive motor 18’ is deactivated, in order to move each cut segment away from the cutting line 16 and the remainder of the concrete member. The cut segments 90 may then be offloaded from the transport bed second portion 12”, for example by using a fork lift truck (not shown).

It will, however, be most convenient if both the first and second portions of the conveyor 30’, 30” are moved in unison until all the concrete members have reached the corresponding desired longitudinal positions prior to cutting.

The free-wheeling rollers 36 provide, for each track portion, a linear bearing 40 that extends along each track portion. The first track portion 12’ has a first portion of the linear bear 40’ and the second track portion 12” has a second portion 40” of the linear bearing. The linear bearing 40 permits relative longitudinal movement between the corresponding supported concrete member and the conveyor 30 on which the member is supported. The linear bearing is passive but like most practical bearings is not frictionless. The static friction and dynamic friction naturally present in the rollers will allow the conveyor to accelerate and decelerate the supported members at the modest accelerations needed move the members into position, for example an acceleration of the order of about 10 to 100 mm/s2 The conveyor 30 therefore imparts longitudinal movement to each concrete member 101-111 through each linear bearing 40’, 40” as the concrete members are transported towards the desired longitudinal positions.

Once each concrete member reaches the desired longitudinal position the restraining system 50 is used to restrain each of the concrete members 10 in the desired longitudinal position. When the restraining system is used to hold a concrete member in place, the linear bearing 40 isolates the held member from any continued movement of the conveyor. In this example, each of the rollers of the track supporting a restrained concrete member will rotate if that track continues to be moved by the corresponding drive motor 18’, 18”. The conveyor thus does not impart any further longitudinal movement to the restrained member. The conveyor 30 does, however, continue to move each of the un-restrained concrete members until each member is, in turn, held in place at a corresponding desired longitudinal position by the restraining system 50.

The restraining system 50 comprises a plurality of brake members 24, one for each of the concrete members 101-111 supported on the tracks 201-211. The brake members are independently operable to restrain each corresponding member in the desired longitudinal position.

The brake members 24 are preferably arranged in a line parallel with the cutting line 16.

The brake members 24 are preferably configured to press on an upper surface 42 of the elongate pre-stressed concrete members 10 in order to restrain longitudinal movement of the members.

In this example, the brake members each comprise a downwardly acting hydraulic piston 38, each piston terminating in a foot 44 that is configured to press downwardly on a corresponding one of the concrete members.

As can be seen most clearly in Figure 5, the tracks 201-211 are each separated by a gap 48 sufficiently wide to provide a gap 52 between adjacent concrete members 101-111. The concrete members therefore do not rub against each other when some are restrained and others continue to be moved by the conveyor.

The gap 48 between tracks is set by the transverse spacing of the rollers 36 for adjacent tracks. The rollers are spaced laterally apart along the beams 28, which move the rollers in unison as both chains 26’, 26” are driven around a loop by the motor drive system 18.

Each of the rollers has an axis of rotation 46 that extends substantially perpendicularly to the length of the corresponding linear bearing 40. Each roller also has a pair of flanges 54, the flanges of the rollers being spaced longitudinally apart along the length of each corresponding track to provide transverse alignment of the concrete members supported on the tracks. It would, however, be possible for each roller to have just one flange, in which case alternate rollers could have flanges on alternate transverse sides in order to provide transverse alignment of the concrete members in both transverse directions.

Preferably, the concrete cutting apparatus 100 apparatus further comprises a clamping system 60. The clamping system is proximate the transport bed first portion 12’, so that the clamping system can restrain concrete members supported by the track first portions 20’ during cutting of the concrete members by the saw 14. The cut segments 90 are therefore held in place on one side of the cutting line 16 by the restraining system 50 while the remaining portions of the concrete members are held in place on the other side of the cutting line by the clamping system 60.

The clamping system comprises a downwardly acting bar 56 that is configured to press downwardly on all of the concrete members 101-111 at the same time. The bar is supported at opposite ends by a hydraulically driven piston 58 which is operable to move the bar down into contact with the restrained concrete members prior to cutting and then move the bar up and off the remaining portions of the concrete members after cutting. To ensure a good contact across the concrete member top surfaces 42 which may not be exactly level within a tolerance of about ±1 mm, the bar comprises a rubber contact strip 57 along its lowermost edge.

Reference is now made particularly to Figures 7 to 17, which illustrate schematically the operation of the concrete cutting apparatus 100. The distance measurement system 70 is configured to generate a measure of the longitudinal position for each of the concrete members 101-111 as these are transported into position by each the tracks 201-211. The distance measurement system 70 comprises a plurality of lidar sensors 62, one for each concrete member. Each lidar sensor is located proximate an end 64 of the tracks 20 and is configured to measure a distance from a reference point to an end face 66 nearest the sensor of the corresponding concrete member. In this example, the reference point is the lidar sensor itself, as the sensor combines both a laser transmitter 68 and a laser receiver or photodetector 72.

Although the concrete cutting apparatus 100 could be controlled manually, it is preferred if the apparatus further comprises a control system 80 which is used to automate control of at least some aspects of the apparatus, in particular the transport of each concrete member towards its final longitudinal position prior to cutting, and the operation of the restraining system.

The control system 80 will, in general be a micro-processor-based electronic system, and is operatively connected to the motor drive system 18, the restraining system 50, and the clamping system 60. The control system 80 may also be operable to activate and drive the saw and carriage 14, 15, however for safety reasons it is preferred if the initiation of cutting is always under the manual control of an operator who oversees the operation of the concrete cutting apparatus.

As shown in Figures 7 and 8, after the concrete beams have been deposited on the transport bed first portion 12’, the first drive motor 18’ is activated by the control system 80 to move the concrete members in unison in a forwards longitudinal direction 74 towards the cutting line 16 and the transport bed second portion 12”.

If the second drive motor 18” has not been activated at the same time as the first drive motor 18’ then as shown in Figure 8, by the time the concrete members have reached the transport bed second portion 12”, the second drive motor 18” will have been activated by the control system 80 so that both transport bed sections are driven in unison from thereon, including both direction and speed.

Optionally, the transport bed includes for each track a statically mounted idler roller 76 positioned between the first and second portions 12’, 12” of the transport beds. The idler rollers 76 provide additional support proximate the cutting line 16, and help to ensure correct alignment as the end face 66 of each concrete member is moved from the first portion to the second portion of the transport bed.

The lidar sensors 62 are then activated to project towards each of the concrete member end faces 66 a 1 mW average intensity pulsed beam of red laser light 65. Some of the light 67 will be scattered off the end face and be received by the lidar sensors. A processor, which may either be part of each sensor 62 or provided by the controller 80, then determines the distance to the end face from the time of flight for the transmitted and received pulses. During this process, the concrete members 10 are moved at a speed of typically 100 mm/s towards the sensors 62.

The control system 80 comprises a memory that stores a table of the lengths of the segments to be sequentially cut from each concrete member. The control system calculates the length of the concrete beam extending beyond the cutting line 16 from the segment by subtracting the measured distance to the end face 66 from a constant value, which is a previously determined distance from the sensor to the cutting line. This constant value may be initially determined or recalibrated by using the sensors 62 to measure the distance to the end faces 66’ of freshly cut concrete beams while these faces are held in position at the cutting line 16 by the clamping system 60.

Once one of the concrete members 10 comes within about 300 mm of its desired position, the speed of the transport bed is reduced gradually to about 10 mm/s so that the transport bed can be stopped more precisely when that member reaches the desired longitudinal position. If necessary, the control system can drive the transport bed in reverse if the concrete member overshoots the desired longitudinal position. As shown in Figure 9, the restraining system 50 is then activated by the control system 80 to activate one of the hydraulic pistons 38, which then drops its foot 44 into contact with the top surface 42 of the concrete member which has been stopped in the desired longitudinal position. That hydraulic piston then remains activated until the cutting of the members is completed.

As shown in Figures 10 to 12, this process is then repeated with second, third, etc. concrete members until all are held in the correct longitudinal position by the feet 44 of the pistons 38. As shown in Figure 13, the control system 80 then drops the clamping bar 56 onto all the restrained concrete members, following which the saw and carriage 14, 15 are activated to cut through the restrained members along the cutting line, as shown in Figure 14. As shown in Figures 4 and 6, the saw also comprises a series of water sprinklers 74 which spray water (not shown) onto the saw concrete beams to cool the saw and trap and wash away concrete dust.

Although not illustrated, optionally, there may be a series of hydraulic anvils located underneath the concrete members, and operatively connected to the control system 80. After all the concrete members haven correctly located and held in place and the transport bed 12 has been stopped, the anvils may be brought up to bear against an underside of the each concrete member, preferably directly opposite each of the activated pistons 38 and the activated restraining bar 56, such that the concrete members 10 are clamped securely from both top and bottom sides, and on both sides of the cutting line, during cutting. In this case, it is necessary that the control system 80 moves and stops each of the conveyors 30’, 30” such that the adjacent transverse beams 28 are not in the way of the anvils.

After the saw has been retracted, as shown in Figure 15, the control system 80 retracts the restraining pistons 38 as shown in Figure 16 and then moves the cut segments 90 away from the cutting line as shown in Figure 17, following which the cut segments can be removed from the transport bed section portion 12”. Finally, the control system 80 lifts the clamping bar 56 so that the process can be repeated to cut a subsequent segment from each of the remaining concrete members.

It will be appreciated the tensioning wires 3 within the concrete beams will be cleanly cut by the saw so that these are flush with each cut end face 66”, of the segments 90. Only at the original end faces 96, 96’ of the cast concrete members 10 may there be a need to manually grind down projecting ends of the tendons 3, and this will most conveniently be done before the concrete members are cut into segments 90 as described above, so that no post processing of the cut segments is required.

The cut segments 90, once lifted off the transport bed second portion 12” may then be separated into separate orders, if required.

In summary, the invention provides a manufacturing system in which a conveyor includes for each member at least one linear bearing on which the member is supported. The linear bearings transfer conveyor movement to unconstrained members and isolate constrained members from further movement by the conveyor when the restraining system acts to restrain each member. Once all members have been restrained the conveyor may be stopped following which the members are cut into segments having the desired lengths, which may therefore all be different lengths.

The process described above, from casting to final cutting of the concrete members, is much quicker than prior art processes that relay on using spacers to cast concrete members to defined lengths. It is also not necessary that all of the tracks are used when cutting concrete members, so that smaller orders can be processed promptly, without having to wait until thee are sufficient orders to allow all tracks to be used. The invention therefore provides a more convenient apparatus and method for manufacturing a plurality of elongate pre-stressed concrete members having individual desired lengths.

Claims

1. A concrete cutting apparatus for sequentially cutting from each one of a plurality of elongate pre-stressed concrete members a plurality of cut segments, each cut segment having a desired predetermined length, the apparatus comprising: a transport bed, the transport bed comprising a set of elongate tracks, said tracks each extending in a longitudinal direction and being laterally adjacent to one another and each track, in use, supporting a corresponding one of said members in a side-by-side configuration prior to cutting of each cut segment; a motor drive system, the set of tracks being linked to the motor drive system such that the motor drive system, in use, drives longitudinal movement of the set of tracks, whereby each of said tracks longitudinally transports said corresponding member towards a desired longitudinal position prior to cutting of each cut segment; a distance measurement system, the distance measurement system being configured to measure for said members a longitudinal position of each of said members transported by said tracks; a restraining system, the restraining system being operable to restrain each of said members in the desired longitudinal position; and a saw, the saw being configured to cut along a transversely extending cutting line through said supported members when longitudinally restrained at said desired longitudinal positions, whereby, in use, said desired predetermined lengths of said cut segments are obtained during cutting by the saw; wherein the restraining system comprises a plurality of brake members, one for each of said members supported on said tracks, said brake members being independently operable to restrain each corresponding member in the desired longitudinal position; the transport bed comprises at least one conveyor, each track being linked to the motor drive system by said conveyor whereby said tracks are, in use, driven by said motor drive system through said conveyor, said conveyor being configured to move said tracks in unison as said members are transported towards said desired longitudinal positions; and each track comprises along its length at least one linear bearing on which said members are supported, each of said bearings permitting relative longitudinal movement between the corresponding supported member and said conveyor whereby, in use, said conveyor imparts said longitudinal movement to each of said members through each linear bearing as said members are transported towards said desired longitudinal positions until the corresponding brake member is used to restrain said member in the desired longitudinal position following which the corresponding linear bearing isolates said restrained member from said conveyor and thus does not impart of any further longitudinal movement to said restrained member.

2. A concrete cutting apparatus as claimed in Claim 1, in which the transport bed comprises a first portion and a second portion, said portions extending longitudinally away from each other on opposite sides of said cutting line and thereby providing corresponding first and second portions of each of said tracks.

3. A concrete cutting apparatus as claimed in Claim 2, in which the brake members are proximate the second portion of the transport bed, whereby the brake members are configured to restrain said members supported by the second portions of said tracks during cutting of said members by the saw.

4. A concrete cutting apparatus as claimed in Claim 2 or Claim 3, in which the apparatus further comprises a clamping system, the clamping system being proximate the first portion of the transport bed, whereby the clamping system is configured to restrain said members supported by the first portions of said tracks during cutting of said members by the saw.

5. A concrete cutting apparatus as claimed in any one of Claims 2 to 4, in which the first and second portions of the transport bed have corresponding first and second conveyors.

6. A concrete cutting apparatus as claimed in Claim 5, in which the motor drive system comprises a first drive motor and a second drive motor, the first portions of said tracks being linked to the first drive motor by the first conveyor and the second portions of said tracks being linked to the second drive motor by the second conveyor.

7. A concrete cutting apparatus as claimed in any preceding claim, in which said linear bearing comprises a plurality of rollers, said rollers being spaced longitudinally apart along each track and each roller being free to rotate in response to a difference in longitudinal speed between said conveyor and said restrained member.

8. A concrete cutting apparatus as claimed in Claim 7, in which said conveyor comprises a pair of drive chains and a plurality of beams, said chains each extending in a longitudinal direction around an endless loop in a substantially vertical plane proximate opposite lateral sides of the transport bed and said beams extending in a lateral direction and said chains being connected together by said beams whereby said chains are configured to move said beams in a longitudinal direction as said conveyor is driven by the motor drive system.

9. A concrete cutting apparatus as claimed in Claim 7 or Claim 8, in which the motor drive system is configured to engage with at least one of said chains whereby said chain, in use, is moved around said loop.

10. A concrete cutting apparatus as claimed in any one of Claims 7 to 9, in which rollers for adjacent tracks are spaced laterally apart along said beams, whereby, in use, said rollers are moved in unison as both chains are driven around said loop by the motor drive system.

11. A concrete cutting apparatus as claimed in any one of Claims 7 to 10, in which each of the rollers has an axis of rotation that extends substantially perpendicularly to the length of the corresponding linear bearing.

12. A concrete cutting apparatus as claimed in any one of Claims 7 to 11, in which each roller has at least one flange, the flanges of said rollers being spaced longitudinally apart along the length of each corresponding track to provide transverse alignment of said members supported on said tracks.

13. A concrete cutting apparatus as claimed in any preceding claim, further comprising a control system, the control system being operatively connected to the distance measurement system and the motor drive system, the control system being configured to compare for each of said members said measured longitudinal position with said desired longitudinal position and to use the motor drive system to longitudinally move the corresponding tracks on which each of said members is supported until said measured longitudinal position corresponds with said desired longitudinal position.

14. A concrete cutting apparatus as claimed in Claim 13, in which the control system is operatively connected to the restraining system, the control system being configured to operate the restraining system to longitudinally restrain each of said members when at the desired longitudinal position.

15. A concrete cutting apparatus as claimed in Claim 14, the control system being configured to operate said brake members independently one from another to restrain each corresponding member in the desired longitudinal position.

16. A concrete cutting apparatus as claimed in any one of Claims 12 to 15, when dependent from Claim 6, in which the control system is configured to control the first drive motor and the second drive motor independently from each other, whereby the second portion of each track, in use, when driven by the second drive motor system longitudinally transports a corresponding cut segment away from said cutting line.

17. A concrete cutting apparatus as claimed in any one of Claims 12 to 16, when dependent from Claim 2, in which the control system is configured to use the motor drive system to drive the both the first and second portions of the tracks in unison until said brakes have restrained all of said members in the desired longitudinal positions.

18. A concrete cutting apparatus as claimed in any preceding claim, in which each of said members prior to said cutting of each cut segment extends between opposite first and second ends of said member, the distance measurement system being configured to measure for said members a longitudinal position of the first end of each of said members.

19. A concrete cutting apparatus as claimed in Claim 18, in which each of said segments to be cut from said members extends from said first end to said cutting line.

20. A concrete cutting apparatus as claimed in Claim 18 or Claim 19, in which the distance measurement system comprises a plurality of lidar sensors, each sensor being configured to measure a separation from the first end of a corresponding member to said sensor.

21. A method of sequentially cutting from each one of a plurality of elongate pre-stressed concrete members a plurality of cut segments of desired predetermined lengths using a concrete cutting apparatus, the apparatus comprising a transport bed, the transport bed comprising a set of side-by-side tracks and a motor drive system, a distance measurement system, a restraining system, and a saw, the method comprising the steps of: i) loading a plurality of said concrete members onto the tracks, whereby the concrete members are supported side-by-side on the tracks; ii) using the motor drive system to drive longitudinal movement of the tracks, whereby each of the tracks longitudinally transports a corresponding concrete member towards a desired longitudinal position; iii) using the distance measurement system to measure for the concrete members a longitudinal position of each of the concrete members transported by the tracks; iv) using the restraining system to restrain each of the concrete members in the desired longitudinal position; and v) when each of the concrete members is restrained by the restraining system in the desired longitudinal position, using the saw to cut along a transversely extending cutting line through the concrete members, whereby, said desired predetermined lengths of said cut segments are obtained during cutting by the saw; wherein the restraining system comprises a plurality of independently operable brake members, one for each of the concrete members supported on the tracks and the transport bed comprises at least one conveyor, each track being linked to the motor drive system by said conveyor and each track comprises along its length at least one linear bearing on which the concrete members are supported, each of said bearings permitting relative longitudinal movement between the corresponding supported member and said conveyor, the method further comprising in step ii) using the motor drive system to move said tracks in unison, said conveyor imparting said longitudinal movement to each of said unconstrained members through each linear bearing as said members are transported towards said desired longitudinal positions until in step iv) the corresponding brake member is used to restrain a corresponding concrete member in the desired longitudinal position following which the corresponding linear bearing isolates said restrained concrete member from said conveyor and thus does not impart of any further longitudinal movement to said restrained member as the motor drive system moves the tracks in unison and unconstrained members continue to be transported towards said desired longitudinal positions until all of the concrete members have been restrained in corresponding desired longitudinal positions by corresponding brake members.

22. A method as claimed in Claim 21, in which the transport bed comprises a first portion and a second portion, said portions extending longitudinally away from each other on opposite sides of said cutting line and thereby providing corresponding first and second portions of each of said tracks, wherein in step i) the plurality of said loaded members is supported by said first portion of said tracks and in step ii) the said cut segments are supported by said second portion of said tracks.

23. A method as claimed in Claim 22, in which the motor drive system comprises a first drive motor and a second drive motor, the first portions of said tracks being linked to the first drive motor by the first conveyor and the second portions of said tracks being linked to the second drive motor by the second conveyor, the method comprising in step ii) using both the first drive motor and a second drive motor to move said tracks in unison and after step v) using just the second drive motor to move said cut segments away from said cutting line for subsequent unloading from the second portions of said tracks.

24. A method as claimed in Claim 22 or Claims 23, in which the apparatus further comprises a clamping system, the clamping system being on an opposite side of the cutting line from the brake members, in which the method comprises after all of said members have been restrained by the corresponding brake member on one side of the cutting line the step of using the clamping system to further restrain each of said members on the other side of said cutting line.

25. A method as claimed in any one of Claims 21 to 24, in which the motor drive system is used to maintain all of said tracks stationary during the operation of each of said independently operable brakes.

26. A method as claimed in any one of Claims 21 to 24, in which the concrete cutting apparatus further comprises a control system, the control system being operatively connected to the distance measurement system and the motor drive system, the method comprising the step of using the control system to compare for each of said members said measured longitudinal position with said desired longitudinal position and to operate the motor drive system to longitudinally move the corresponding tracks on which each of said members is supported until said measured longitudinal position corresponds with said desired longitudinal position.

27. A method as claimed in Claim 26, in which the control system is operatively connected to the restraining system, the method comprising the step of using the control system to operate the restraining system to longitudinally restrain each of said members when at the desired longitudinal position.

28. A method of manufacturing a plurality of elongate pre-stressed concrete members each having a predetermined desired length, the method comprising the steps of: i) setting at least one tensioned tendon into each of at least two casting troughs, said troughs each having opposite ends; ii) pouring concrete into the troughs, and allowing the concrete to set around said tendons to form a plurality of elongate pre-stressed concrete members each concrete member extending between the opposite ends of the corresponding casting trough; iii) removing the concrete members from said troughs; and iv) sequentially cutting from each one of said plurality of elongate pre-stressed concrete members a plurality of cut segments having said predetermined desired lengths using the method of any one of Claims 21 to 27.

29. A concrete cutting apparatus for sequentially cutting from each one of a plurality of elongate pre-stressed concrete members a plurality of cut segments, each cut segment having a desired predetermined length, the apparatus being substantially as herein described, with reference to or as shown in Figures 4 to 17 of the accompanying drawings.

30. A method of sequentially cutting from each one of a plurality of elongate pre-stressed concrete members a plurality of cut segments of desired predetermined lengths using a concrete cutting apparatus, the method being substantially as herein described, with reference to or as shown in Figures 4 to 17 of the accompanying drawings.

31. A method of manufacturing a plurality of elongate pre-stressed concrete members each having a predetermined desired length, comprising casting a plurality of elongate pre-stressed concrete members and then sequentially cutting from each one of said cast concrete members a plurality of cut segments having said predetermined desired lengths using a concrete cutting apparatus, the method being substantially as herein described, with reference to or as shown in Figures 4 to 17 of the accompanying drawings.