MOULDING ASSEMBLY

The present invention relates to a moulding assembly and a method of making a moulding assembly and to a method of moulding. The present invention is particularly, although not exclusively concerned with moulding assemblies for moulding concrete.

Figure 1 is a schematic sectional view of a pre cast concrete unit forming machine 10. The concrete 12 is cast into a suitably shaped mould defined by peripheral solid upwardly extending walls 14 (only two of which are shown) and a porous fabric face filter 16. A piston 18 is then pushed down towards the concrete 12 to urge a porous fabric back filter 20 against the concrete. In this way some of the water in the concrete is squeezed out.

The face fabric filter 16 is of a relatively fine weave or knit as this is the face of the kerb that will, in use, be visible. The back filter is of less fine weave or knit as this will comprise the underside of the pre cast concrete unit .

The back filter is shown in more details in Figures 2 and 3. In all instances, a polypropylene plate 22 is used which is relatively rigid. The plate 22 is 1.5 or 2 mm thick and includes openings 25 through the plate. The openings are in parallel rows with the diameter of each opening being 2.84 mm and with the centre of adjacent openings in a row being spaced from each other by 5.33 mm. The centres of alternate rows are spaced from each other by 9.23 mm or the centres of openings in adjacent rows are offset from each other such that the distance from the

centre of an opening in one row is the same to the centre of the nearest adjacent openings in a row to one side. The plate may be of a cross section such as 10 x 10 cm or 900 x 600 mm or 600 x 200 mm, for example.

Figure 2, comprising a schematic view of the face of the filter that will abut the concrete, shows one method of securing fabric 24 to the plate 22. The fabric 24 is secured to the plate 22 inwards of the edges by stitches 26 that extend in rows through the fabric and through the plate 22. The stitches are necessarily inwards of the edge, for instance by at least 150 mm. The stitches maintain the fabric in contact with the plate at at least the regions where the stitches are located.

Figure 3 is a side view showing how the fabric can be secured to the plate at the edge region. The stitches of Figure 2 will also be used. The fabric 24 is folded around the side edges 28 of the plate and then back over onto the side 30 of the plate that faces away from the concrete. Double sided adhesive tape 32 secures the fabric to the back of the plate.

In the above filters though, be they back or face filters, the life of the filter can be relatively short. This is particularly so for the back filters. The sides 28 of the filters must be a close fit to the surrounding wall 14 of the process in to minimise the leakage of any components of the concrete around the sides of the filter. Thus there is considerable wear at the sides. The wear is exacerbated by the severe abrasive effect of the concrete components which will include fine particles of sand and aggregate for instance.

After minimal wear through the fabric at the sides, components of the mix can escape at discrete locations around the side to occupy the space between the filter fabric 24 and the surface of the plate that faces the concrete, as shown by the dotted line bulge 32 in Figure 3. Such a bulge produces unsatisfactory articles and requires replacement of the filter. The problem of wear is particularly acute as the fabric, which is very prone to wear, rubs against the walls of the mould rather than the tougher, thicker surface of the plate 22.

A further problem with the manufacture of the prior filters is maintaining the tension in the fabric across the surface of the plate both during manufacture and in use .

It is an object of the present invention to attempt to overcome at least some of the above or other disadvantages.

According to one aspect of the present invention a moulding assembly includes a porous support member having a moulding surface arranged, in use, to face a material being moulded and a fabric filter extending over the moulding surface characterised in that the fabric filter is attached to the support member at least partially by welding .

According to another aspect of the present invention a method of making a moulding assembly in which the assembly includes a porous support member having a moulding surface arranged, in use, to face a material being moulded is

characterised in that a fabric filter is extended over the moulding surface and attached to the support member welding .

According to another aspect of the present invention there is provided a moulding machine comprising a welding member for welding a fabric filter to a support member, wherein the machine includes a blade and the blade trails the welding member such that, in use, the blade separates material on one side of the weld from material on the other side when movement of the welding member and blade relative to the material occurs.

Preferably the blade separates the material along one edge of the weld. The blade may, in use, slide against an edge of the support member.

Preferably the machine includes at least one sensor. The machine may include a first sensor for detecting when the fabric filter and additionally or alternatively the support member are positioned under the welding member. The sensor may control the welding member. The sensor may start and additionally or alternatively stop the weld member. The sensor may cause the welding member to move. The machine may include a second sensor. The first sensor may impinge on an area leading the welding member. The second sensor may impinge on an area trailing the welding member .

Preferably the machine provides an air stream directed towards the weld.

Preferably the welding member is moveable by drive means. The sensors may be movable by the drive means. The blade may be movable by the drive means . The air stream may be movable by the drive means . The drive means may move the or each part at a constant rate. The drive means may comprise a belt drive.

Preferably the machine includes a movable datum. The datum may be movable between a first stored position, wherein the datum is arranged clear of a welding area, and a second, useable position, wherein the datum provides a reference to align the support member. The machine may include at least one bellow and the or each bellow may move the datum. The datum may provide the reference by providing an abutment face.

Preferably the machine incorporates at least one moulding assembly as herein described.

Other features of the present invention are included in the claims.

The present invention includes any combination of the herein referred to features and limitations.

The present invention can be carried into practice in various ways but one embodiment will now be described by way of example and with reference to the previous and the following drawings, in which: -

Figure 4 is a perspective sectional view of part of a filter;

Figure 5 is a sectional view of part of the filter of Figure 4 ;

Figure 6 is a detailed view of the edge of the filter shown in Figure 4 ;

Figure 7 is a schematic side view showing one arrangement for effecting the attachment of the fabric to the plate as shown in Figure 5;

Figure 8 is a schematic side view of an edge welding machine;

Figure 9 is a plan view showing the area of the welder and the relationship to the edge of the sheet, and

Figure 10 is a side view of a trimming machine.

Figure 11 is a schematic side view showing a second embodiment of the welding machine;

Figure 12 is a schematic front view of the second embodiment .

The plate and fabric will be used as described in relation to the previous figures. The plate is polypropylene.

The fabric of the back filter may be a woven fabric having warp of a multifilament polyester of 20 ends/cm and a weft comprising a monofilament polyester of 20 picks/cm. The weave may be 3/1 broken twill. The weight may be 400 gsm.

The fabric of the face filter may be a warp of multifilament polypropylene having 21 ends/cm with a weft comprising a monofilament polypropylene of 25.5 picks/cm. The weave may be a 3/1 broken twill. The weight may be 250 gsm.

Whilst a woven fabric has been described having particular qualities and being of a particular material it will be appreciated that other weaves of different weight or material or non-woven fabric could be employed as could other fabrics such as knitted fabrics or needled fabrics, such as felt.

Referring now to Figure 4, the back fabric 24 extends over the part of the plate that will face the concrete. The fabric 24 is welded to the plate at every third opening 25 and also around the periphery of the plate, as shown by the weld 34, on the same surface of the plate that faces the concrete.

As shown in Figure 5, the weld 36 of the fabric 24 to the openings 25 is around the peripheral ring of the opening at the outer region of the opening. In this way the porosity of the filter remains the same as the water can still flow through the fabric over the weld and through the opening 25. There may also, optionally, be stitches that hold the fabric to the plate. In an alternative embodiment the fabric is stitched to the plate, possibly without any welds to the openings. In some instances the weld need not be continuous about the opening and two or more spaced welds may be provided at an opening. Alternatively or additionally welds could be provided between the fabric and the plate away from the openings,

for instance at spaced intervals. A machine for clamping the plate and fabric and effecting the side welds will be described below. This machine could also be used to weld the sheets to the fabric away from the sides at spaced intervals. This may be effected by releasing the clamp and sliding the plate beneath the welder and advancing the welder over the plate and fabric to make the welds at spaced intervals generally in a line. Further advancement of the plate and sheet can then be made to effect further welds at spaced intervals in lines parallel to the first line .

By welding the fabric to the openings the fabric can be maintained taut over the surface of the plate. The centre weld or welds in the centre region may be applied first, for instance to register the fabric on the plate, with outer welds then being applied, for instance progressively outwardly, such as progressively outwardly around the initial weld or welds in order to impart stretch or to maintain the fabric tight over the surface of the plate. In this respect, it can be seen in Figure 5 that the fabric 24 is depressed slightly into the opening 25 thereby tensioning or stretching the fabric.

As an alternative to the central weld or welds being supplied initially, outer weld or welds may be applied initially with inner welds subsequently being supplied, for instance by being applied progressively inwardly to tension the fabric or to stretch the fabric. Alternatively the peripheral welds at one or all edges may be effected prior to any inner welds being made.

Alternatively or additionally, the welds could be applied to one row or a plurality of rows at a time with subsequent rows then being welded to the openings. For instance the first row or rows with the first welds could be located at a side, or side region of the plate with a subsequent parallel row or rows then being welded progressively across the plate. Alternatively a row or rows extending from the middle region of opposed sides of the plate could be welded initially with an outer row or rows then having the welds applied to them, for instance by progressively welding an adjacent row or rows progressively outwards from the initial row or rows either simultaneously on each side or by first being welded on one side and then the other. An adjacent row or rows to one side may be welded at the same time as an adjacent row or rows to the other side of the initially welded row or rows or at different times.

It will also be appreciated that the welded regions 34 or 36 will be of greater wear resistance than the fabric alone. Consequently the fabric is allowed to live its full life before replacement of the filter is required.

Referring now to Figures 4 and 6, the fabric 24 and plate 22 are welded over a distance of 1.5 mm over their coextent, when viewed in Figure 4. The sides of the plate and the excess fabric 40 that overhangs the plate are then cut along the line 42 to arrive at the arrangement shown in Figure 6. In this arrangement approximately 0.5 mm or less, such as 0.25 or 0.3 or 1 mm of the weld 34 between the plate and the fabric remains. In Figure 6 it can also be seen that the outer side of the 1.5 or 2 mm thick plate has been depressed at the outer edge by about 0.1 mm

as a result of the welding process to give a bevelled edge. The compression at the edge region may increase the wear resistance at that location. The bevelled edge is a result of the angle of the ultrasonic welder's tip. It has been found that an tip angle of approximately 45° gives optimum results.

Looking at Figures 4 and 6 it can be seen that it is only the edges 28 of the relatively hard and wear resistant plate 22 that will slide against the walls of the mould. Consequently the edges will only be ground away gradually. Furthermore, as the hard edges gradually wear the integrity of the filter is maintained as the fabric is welded to the plate at the edge on the operative sides. Failure of the filter at the edges will only occur when the wear extends to a position where the side welds are compromised. Thus the life of the filter is significantly enhanced. It can also be seen that the weld does not weld all the fabric. Thus water can still flow over the weld.

The welds in accordance with the present invention are, preferably but not necessarily, ultrasonic welds in which pressure and vibrations are applied to effect the joining. Preferably the welds are such that there is no damage to the plate or fabric other than to create a bond at the coextensive surfaces. Thus, as seen in Figures 5 and 6, the fabric above the weld, such as the majority of the thickness of the fabric, remains a fabric.

A welding machine for effecting the welds at the openings 25 is shown schematically in Figure 7. The plate and fabric are driven through a pair of driven rollers 44 the upper one of which includes projections 46 that urge the

fabric down into every third opening 25 to very limited extent. At the same time pressure is applied by the spacing of the rolls 44 to urge the fabric against the rim and to effect the welding.

Figure 8 shows a machine for effecting the edge welded regions 34. The machine includes a base 50 for supporting the plate 22 with the fabric 24 on top. The base 50 includes a channel 52 towards one side and the plate is moved to overlap that channel to a small degree. The plate is held in position by pneumatically activated clamps 54 that are mounted in bars 56 above the plate. Each end of the bars are supported by end mountings 58, only one of which is shown.

The initial clamping force is small, allowing the plate to be accurately positioned. This may be assisted by placing a spacer (not shown) in the channel, of less width than the channel and sliding the plate up to abut the spacer.

The welding is now performed after the grip effected by the clamps has been automatically increased. An ultrasonic welder 60 of arcuate section is urged down to bias the fabric towards the plate and moved along the edge to effect the weld 34 shown in Figure 6. Movement and biasing of the welder 60 may be manually effected or automated. A guide rail for the welder (not shown) is provided.

After effecting the edge weld the clamp may be relaxed and the plate rotated to effect the other side welds. Prior to or after effecting the other side welds the clamp may be relaxed and the plate moved in steps in the direction

of arrow A to cause the plate to extend progressively over and further beyond the channel 52. The progress of the plate can be halted in steps by further clamping with the welder effecting spot welds along the plate in a line.

The welding of the edges is effected with the fabric overhanging the edges. Figure 10 shows an edge trimming arrangement. The side of the plate 22 is caused to abut a stop 61 with the excess fabric 62 overhanging the stop 61. An ultrasonic welder 64 then cuts the excess fabric off either by movement of the plate or by movement of the welder. The trimming causes the weld of the fabric to the plate to be further enhanced as shown by the bulge 66 in Figure 6. Consequently the filter is able to function for longer periods as the connection is reinforced at precisely the region where significant wear occurs.

Figures 11 and 12 show an alternative embodiment of the machine wherein, unless otherwise described, the machine is as previously described with like numerals representing like parts.

The machine includes a movable datum bar 70 for positioning the plate 22, rather than a channel 52 as previously descried. The datum bar extends the length of the base 70. It is moveably mounted within the base 50 such that it moves laterally towards and away from the ultra sonic welder 60. The datum bar 70 is movable by a bellow 72 comprising a bag that is supplied and vented with air. Accordingly, the datum bar 70 is movable to a first, raised position by filing the bag 72. In the raised position, the plate 22 is positioned on the base by abutting the plate 22 with the datum bar 70. When

positioned the plate 22 can be clamped by clamp 54 as before. The air in the bag 72 can then be vented, which therefore collapses the bag. Consequently, the datum bar 70 moves to a second, lowered position either due to the weight of the bar or alternatively, the bar is biased towards the second position. The welding operation may then be carried out.

The movable datum bar 70 provides greater accuracy to the alignment of the plate 22 and also improves the manufacturing process. Importantly, the datum bar 70 also moves clear of the plate 22 during the welding process, which avoids excessive heat build up.

According to the second embodiment, the ultra sonic welder 60 is slidably mounted on the machine to move laterally toward and away from the plate 22. Thus, as herein described, the welder 60 can be moved between a stowed position, wherein the welder is spaced clear of the welding area, and an operational position, wherein the welder is spaced close to the welding area. It is advantageous to control the machine so that the ultrasonic welder 60 is not moving across the machine when the welder 60 moves to the operational position as otherwise it tends to burn through the material.

The ultra sonic welder 60 is movable along the length of the base 50 by a belt drive 73. The belt drive 73 is advantageous as it ensures a constant feed of the ultra sonic welder 60 relative to the plate, which improves the quality and consistency of the weld. The machine is controllable so that the ultra sonic welder 60 is

positionable to begin a weld part way through a cycle, should the operation be halted for any reason.

Referring to Figure 12, first and second sensors 74, 76 are arranged on the machine. The sensors are attached fast to the ultra sonic welder 60 in at least the plane of movement of the ultra sonic welder along the width of the base 50. The sensors comprise non-contact sensors capable of sensing changes in height of a surface. For instance, the sensors may be ultrasonic sensors that receive a reflected sound to determine the proximity of an adjacent item.

The first sensor 74 is arranged to detect the height of the base 50 at a position close to the leading tip of the ultra sonic welder 60. As such, when a plate 22 is in position and the ultra sonic welder 60 is moved towards the plate 22, the first sensor 74 detects the change in height. Alternatively or additionally, the first sensor 74 may automatically switch the ultra sonic welder 60 on when a plate 22 and fabric 24 are in position. Alternatively or additionally, the first sensor 74 detects the plate 22 and fabric 24 and switches the ultra sonic welder 60 to move downwardly from the stored position towards the base 50 to the operational position. The ultra sonic welder is caused to turn on when in the operational position. As the tip of the ultra sonic welder 60 is stored out of the way, the risk of damage when loading plates 22 is reduced.

The second sensor 76 trails the welder 60 and therefore detects a change in height when the ultra sonic welder runs off the end of the plate 22. The sensor 76 therefore

switches the ultra sonic welder 60 off and may additionally also cause the ultra sonic welder 60 to return to the stored position. Whilst the first sensor 74 may be used to detect the start and end of the plate on its own, it is preferable to use two sensors as the welder may then be used bi-directionally.

Still referring to Figure 12, an air supply hose 78 is also provided which moves with the welder 60. The air supply hose 78 is arranged to direct a stream of air onto the weld and tip of the ultra sonic welder. The stream of air acts to cool the area, which improves the quality of the weld and also increases the performance and life of the ultra sonic welder 60.

Referring to Figure 11, the second embodiment of the machine also includes a cutting head 80. As shown in Figure 12, the cutting head 80 includes a blade 61. The blade 61a is attached to the belt drive 73 and rotates and moves laterally along the width of the base, trailing the ultra sonic welder 60. When the plate 22 is positioned, the blade 61a slides against the plate 22 or slides adjacent or spaced immediately next to the plate 22 in order to trim the fabric 24 to the plate 22. Accordingly, as the ultra sonic welder moves relative to the plate 22 and creates the weld, the trailing blade 61a separates the discarded fabric from the filter along the already softened weld edge.

Advantageously, the second embodiment enables the excess fabric to be removed from the filter in one step rather than having to trim the fabric after forming the weld.

The machine may be adapted to include movement of the ultrasonic welder along the depth of the machine so that any 2-dimensional pattern of weld may be affected.

Due to the welding and cutting process creating loose fibrous material that tends to block the rail and other sliding parts, it is advantageous if such parts include brushes or other means to clean the rail parts so that the sliding parts do not become blocked.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification

(including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.