EP0612888A1

EP0612888A1 - Improvements in or relating to cores for drainage elements or the like and method of manufacturing same

Info

Publication number: EP0612888A1
Application number: EP93301286A
Authority: EP
Inventors: Alan Bamforth
Original assignee: Marshall Richard
Current assignee: Marshall Richard
Priority date: 1991-06-04
Filing date: 1993-02-22
Publication date: 1994-08-31
Also published as: GB9111957D0; GB2258792B; GB2258792A

Abstract

A core (10) for forming a drainage element for use in forming sub-surface drains comprises a base plate (12) of plastics material having a plurality of spaced-apart frusto-conical projections (14) formed thereon extending from one or both sides of the base plate (12), each projection (14) including strengthening ribs or grooves (16) extending from the base to the top thereof. The core (10) is wholly or partially enclosed in a layer of geo-textile filter material (32) to form a drainage element.

Description

This invention relates to cores for drainage elements or the like and more particularly, but not exclusively, to drainage elements for use in forming sub-surface drains.
Prefabricated sub-surface drains; which are used to remove excess water from the ground in order to, for example, improve crop growth, stabilise the ground and strengthen foundations; normally comprise layers of filter material which are held in spaced-apart relationship by a core so that water entering the element through the filter material is allowed to drain through the cavity formed by the core between the filter material.
Known cores usually include projections which extend transversely between the layers of filter material. However, it will be appreciated that the ground in which the drain is inserted exerts a compressive pressure on the drain and such known drains often suffer from the disadvantage that part or sections of the core collapse under compression or sustained long term loading causing a blockage in the drainage channel formed between the layers of filter material by the core.
The object of this invention is to provide a core for use in a drainage element having an improved strength to weight ratio so as to be capable of withstanding greater compressive loads than known cores of equal weight and for similar spacing of projections and thickness.
According to one aspect of this invention, a core for use in a drainage element comprises a base plate having a plurality of spaced-apart projections formed thereon, wherein the or each projection includes one or more strengthening ribs or grooves extending at least partially of the height of the associated projection.
Preferably, the projections formed on the base plate extend both upwardly and downwardly from opposite sides thereof.
Preferably, also, the ribs or grooves extend for the full height of the associated projection from the base to the top thereof.
Each projection is, preferably, frusto-conical in shape.
Preferably, the ribs or grooves are equi-angularly spaced-apart around the curved surface of the associated projection.
Preferably, also, the projections are formed in the base plate material by a moulding operation.
The core is, preferably, formed of a plastics material, such as high density polyethylene or similar material, by a thermo-forming process.
Preferably, the core is tapered in cross-section so that the height of the projections increases from one side edge of the core to the opposite side edge thereof.
Preferably, also, the core is impermeable to the transmission of liquids from one side thereof to the other.
Alternatively, the core is adapted to be permeable to liquids by providing apertures in the base plate in the areas thereof between the bases of the projections.
According to another aspect of this invention, a drainage element comprises a core according to said one aspect of this invention having a layer of filter material mounted thereon.
Preferably, the layer of filter material is mounted on the tops of the projections.
Preferably, also, layers of filter material are disposed on both sides of the core.
The core is, preferably, disposed within an envelope of filter material so that both of the sides and the edges of the core are enclosed therewithin.
Preferably, where the core is of tapered cross-section, the envelope of filter material enclosing the projections of greatest height forms together therewith an integral drainage tube section.
Preferably, also, the envelope of filter material extends beyond the edge of the core at one side edge thereof to enable a separate conventional drainage pipe to be inserted slidably therein to form a drainage tube section.
The filter material is, preferably, secured to at least the tops of the projections on one side of the core.
Preferably, the filter material is secured to both sides of the core.
Preferably, also, the filter material is secured to the core by means of adhesive, by bonding, or by fusion of the core and filter material.
Preferably, also, the filter material is a geo-textile fabric.
According to a further aspect of this invention, a method of forming a drainage element according to said other aspect of this invention comprises drawing a length of core material according to one aspect of this invention from a supply, drawing a sheet of filter material from a supply so that the core is disposed in the central area of the filter material with the projections extending from one side of the base plate of the core in contact with filter material, and folding both of the edge portions of the filter material projecting beyond the sides of the core onto the top surface of the core to contact the base plate or the tops of the projections extending from the opposite side of the base plate.
Preferably, the edge portions of the filter material are brought into overlapping engagement and are secured together to enclose the core therewithin and form the drainage element with a single joint line..
Preferably, also, one edge portion of the filter material is folded over an additional plate disposed at one side edge of the core before being brought into overlapping engagement and being secured to the other edge portion of the filter material and/or to the core, thereby forming a sleeve at one side edge of the core into which a drainage tube can be inserted.
The base plate of the core is, preferably, secured to the filter material.
Preferably, the tops of the projections of the core are secured to the filter material.
Preferably, also, the overlapping edge portions of the filter material, the base plate of the core and the filter material, and the tops of the projections and the filter material are secured by means of adhesive, by fusion, or by bonding.
Preferred embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings of which :-

Figure 1 is a diagrammatic perspective view of a core;
Figure 2 is a diagrammatic perspective view of an alternative core;
Figure 3 is a diagrammatic sectional side view of a drainage element having a core as shown in Figure 1 of the drawings;
Figure 4 is a diagrammatic sectional side view of an alternative drainage element;
Figure 5 is a diagrammatic plan view of a machine for manufacturing a drainage element; and
Figure 6 is a diagrammatic side view of the machine shown in Figure 5 of the drawings.

Referring now to Figure 1 of the drawings, in one embodiment of the invention a core indicated generally at 10 comprises a base plate 12 having a plurality of projections 14 formed thereon. The projections 14 are of frusto-conical shape and are each provided with ribs or grooves 16 in the curved surface of the associated projection 14. The ribs or grooves 16 are equi-angularly spaced-apart around the curved surface of the frusto-conical projection and extend for the full height of the projection 14 from the base to the top thereof.
The ribs or grooves 16 in the curved surface of the projections 14 increase the ability of the core 10 to withstand compressive loading imposed on the tops of the projections 14 without increasing the thickness of the material and thus the weight of material used to form the core 10. The formation of the projections 14 with ribs or grooves extending for the full height of the associated projection 14 from the base to the top thereof provides optimum strength under compressive loading but it is of course possible to provide ribs or grooves which extend for only part of the height of the associated projection if required.
The core 10 is formed of a plastics material by a thermo-forming process, the projections 14 being produced as hollow formations from the material of the base plate 12. The formation of the ribs or grooves 16 in the curved surface of the frusto-conical projections 14 is particularly suitable for production by vacuum or pressure forming and suitable plastics materials are high density polyethylene, high impact polystyrene or the like.
The base plate 12 is either left as a complete sheet so that the core 10 is impermeable to the transfer of liquid from one side to the other or a plurality of holes or apertures (not shown) are formed in the base plate 12 between the projections 14 to make the core 10 permeable to the transfer of liquid where this is desirable.
An alternative shape of core indicated generally at 20 is shown in Figure 2 of the drawings. In this alternative core 20, the projections 22 are of reduced height and greater area than those of the core 10. Strengthening ribs or grooves 24 are again formed on the curved surface of the frusto-conical projections 22 and although this core 20 is of a different shape to the core 10 it is produced by the same method and from the same material as the core 10.
In a modification, the core is formed with projections extending upwardly from one side of the base plate and downwardly from the opposite side of the base plate. The two sets of projections can be of equal or different heights.
Referring now to Figure 3 of the drawings, in another embodiment of this invention a drainage element indicated generally at 30 comprises a core 10 as described above in said one embodiment.
The core 10 is enclosed in an envelope of filter material 32 formed of, for example, a geo-textile fabric. The filter material 32 is secured to the tops of the projections 14 by adhesives, by fusion or by bonding. The filter material 32 can also be secured to the base plate 12 by adhesives, by fusion or by bonding.
Where the filter material 32 encloses the core 10 in a complete envelope, it is desirable for the base plate 12 to be provided with holes or apertures so that it is permeable to the transfer of liquid from one side to the other.
In a modification, particularly suitable where the base plate 12 at the core 10 is impermeable to liquid, the filter material 32 is only provided on one side of the core 10 extending across and secured to the tops of the projections 14.
In another modification, the envelope of filter material 32 is extended at the lower edge of the core 10 to form a sleeve into which a drainage tube can be inserted to carry away the liquid which drains into the core 10 through the filter material 32 from the ground into which the drainage element 30 is installed.
Referring now to Figure 4 of the drawings, an alternative drainage element 40 comprises a core 42 having similar projections 44 to the previously described cores 10 and 20 but the height of the projections 44 increases towards the lower side of the element 40 so that it is of tapered cross-section.
The core 42 is again enclosed in an envelope of filter material 46 as previously described.
The larger cross-sectional area of the element 40 at the lower side thereof increases the volume of liquid which can be drained therethrough so that the provision of a separate drainage tube is obviated.
Referring now to Figures 5 and 6 of the drawings, a machine indicated generally at 50 for the continuous production of the above described drainage elements comprises a table 52 having a supply roll of core 54 and a supply roll of filter material 56 at one end and a haul -off unit 58 at the opposite end for drawing the finished drainage element 60 off the table 52 where it is collected on a wind up roller 62.
The core 54 is drawn onto the table 52 through a bonding unit 64 which applies adhesive to one or both sides of the core 54. The filter material 56 is drawn onto the table so that it is disposed beneath the lower projections extending from the core 54.
The core 54 and filter material 56 pass over a forming roller 66 and beneath a pressure plate 68 to secure the filter material 56 to the lower projections extending from the core 54.
The forming roller 66 is not greater in width than the width of the core 54 to enable the side portions of the filter material 56 to be folded upwardly and inwardly onto the top of the base plate or projections of the core 54 as the filter material 56 and core 54 move further along the table 52.
One side portion of the filter material 56 passes around a sleeve forming plate 70 before the two edges of the filter material 56 are drawn together on top of the core 54 and secured to the core 54 by adhesive to complete the formation of the drainage element 60. The position of the plate 70 is adjustable to vary the size of sleeve portion 72 which is formed at the side edge of the drainage element 60 thereby enabling different diameters of drainage tubes to be fitted to the element. A draw cord 74 is inserted into the sleeve portion 72 to facilitate subsequent insertion of the drainage tubes when installing the drainage element in the ground.
The utilisation of this method of forming the drainage element 60 enables the element to be continuously produced with only a single joint line of the filter material even where a drainage tube sleeve is provided.
Although the above described cores are particularly suitable for use in drainage elements they can be used for other purposes without departing from the scope of this invention.
Amongst other uses, it is envisaged such cores can be used as a void former in access flooring, in other fabrications such as door or wall panels, liners for cooling towers, a crushable cushion layer for energy absorption, for use in gas vents or fixing systems for securing heating pipes to walls or floors.

Claims

A core for use in a drainage element comprising a base plate having a plurality of spaced-apart projections formed thereon, wherein the or each projection includes one or more strengthening ribs or grooves extending at least partially of the height of the associated projection.
A core according to Claim 1, wherein the projections formed on the base plate extend both upwardly and downwardly from opposite sides thereof.
A core according to Claim 1 or Claim 2, wherein the ribs or grooves extend for the full height of the associated projection from the base to the top thereof.
A core according to any one of the preceding claims, wherein each projection is frusto-conical in shape.
A core according to Claim 4, wherein the ribs or grooves are equi-angularly spaced-apart around the curved surface of the associated projection.
A core according to any one of the preceding claims, wherein the projections are formed in the base plate material by a moulding operation.
A core according to any one of the preceding claims, wherein the core is formed of a plastics material by a thermo-forming process.
A core-according to Claim 7, wherein the plastics material from which the core is formed is a high density polyethylene.
A core according to any one of the preceding claims, wherein the core is tapered in cross-section so that the height of the projections increases from one side edge of the core to the opposite side edge thereof.
A core according to any one of the preceding claims, wherein the core is impermeable to the transmission of liquids from one side thereof to the other.
A core according to any one of Claims 1 to 9, wherein the core is adapted to be permeable to liquids by providing apertures in the base plate in the areas thereof between the bases of the projections.
A drainage element comprising a core according to any one of the preceding claims having a layer of filter material mounted thereon.
A drainage element according to Claim 12, wherein the layer of filter material is mounted on the tops of the projections.
A drainage element according to Claim 12 or Claim 13, wherein layers of filter material are disposed on both sides of the core.
A drainage element according to Claim 14, wherein the core is disposed within an envelope of filter material so that both of the sides and the edges of the core are enclosed therewithin.
A drainage element according to Claim 15, wherein where the core is of tapered cross-section, the envelope of filter material enclosing the projections of greatest height forms together therewith an integral drainage tube section.
A drainage element according to Claim 15 or Claim 16, wherein the envelope of filter material extends beyond the edge of the core at one side edge thereof to enable a separate conventional drainage pipe to be inserted slidably therein to form a drainage tube section.
A drainage element according to any one of Claims 12 to 17, wherein the filter material is secured to at least the tops of the projections on one side of the core.
A drainage element according to Claim 18, wherein the filter material is secured to both sides of the core.
A drainage element according to Claim 18 or Claim 19, wherein the filter material is secured to the core by means of adhesive.
A drainage element according to Claim 18 or Claim 19, wherein the filter material is secured to the core by bonding, or by fusion of the core and filter material.
A drainage element according to any one of Claims 12 to 21, wherein the filter material is a geo-textile fabric.
A method of forming a drainage element according to any one of Claims 12 to 22, comprising draining a length of core material according to any one of Claims 1 to 11 from a supply, drawing a sheet of filter material from a supply so that the core is disposed in the central area of the filter material with the projections extending from one side of the base plate of the core in contact with filter material, and folding both of the edge portions of the filter material projecting beyond the sides of the core onto the top surface of the core to contact the base plate or the tops of the projections extending from the opposite side of the base plate.
A method according to Claim 23, wherein the edge portions of the filter material are brought into overlapping engagement and are secured together to enclose the core therewithin and form the drainage element with a single joint line.
A method according to Claim 23 or Claim 24, wherein one edge portion of the filter material is folded over an additional plate disposed at one side edge of the core before being brought into overlapping engagement and being secured to the other edge portion of the filter material and/or to the core, thereby forming a sleeve at one side edge of the core into which a drainage tube can be inserted.
A method according to any one of Claims 23 to 25, wherein the base plate of the core is secured to the filter material.
A method according to any one of Claims 23 to 26, wherein the tops of the projections of the core are secured to the filter material.
A method according to any one of Claims 25 to 27, wherein the overlapping edge portions of the filter material, the base plate of the core and the filter material, and the tops of the projections and the filter material are secured by means of adhesive, by fusion, or by bonding.