GB2315701A

GB2315701A - Mould for concrete pipe socket end

Info

Publication number: GB2315701A
Application number: GB9616158A
Authority: GB
Inventors: Thomas William Wildgoose
Original assignee: Glynwed Pipe Systems Ltd
Current assignee: Glynwed Pipe Systems Ltd
Priority date: 1996-08-01
Filing date: 1996-08-01
Publication date: 1998-02-11
Also published as: GB9616158D0

Abstract

A pallet 2 for shaping and supporting an inner surface of a socket end of a concrete pipe during moulding comprising: (i) a first annular mould element 4 having a radially outwardly extending first flange portion 8 for supporting an outer axial face of the socket end and a radially inwardly extending second flange portion 10 for supporting an inner axial face of the socket end connected by a tubular portion 12, the first flange portion 8 being linked to the tubular portion 12 by a radiussed wall portion 22, the radially outer surface of which defines an annular concave region; and (ii) a separate second annular mould element 6 disposed about the circumference of the first annular mould element 4 and secured within the annular concave region thereof; the element 6 having a radially outwardly facing circumferentially extending concave surface 28 for supporting a radiussed radially inner edge of the socket end, and a radially inwardly inclined surface 32 axially inwardly of the concave surface for supporting a leading edge of a sealing member to be moulded into the socket end.

Description

MOULD MEMBER This invention relates to a pallet for shaping and supporting an inner surface of a socket end of a concrete pipe during a moulding operation, the concrete pipe being of the type which has an elastomeric seal anchored therein.

it is usual to provide an elastomeric seal between the spigots and sockets of two adjacent concrete pipes and a large number of different types of seal have been proposed. In order to prevent axial dispiacement of the seal by the end of the pipe as it is inserted, it is known to anchor the seal within the concrete during the moulding operation. Examples of anchored seals are those disclosed in, for example, GB 2109496, EP 0077918, GB 1409072, GB 2108421, GB 2033293 and EP 0507005.

Methods for manufacturing concrete pipes are well known and typically involve casting the pipe in a mould consisting of an upstanding radially inner tubular core surrounded by a radially outer tubular sleeve, a lower end mould member or pallet, and an upper end mould member. The lower mould member, or pallet, as it is more usually known, serves both to impart a socket shape to the end of the pipe during the moulding process, and also supports the pipe whilst the concrete is setting.

In order to enable it to create a socket formation at the end of the concrete pipe, the pallet typically has a radially outwardly extending flange at one end for shaping and supporting an end face of the pipe, and a radially inwardly extending flange for shaping and supporting an inner axial face at the innermost part of the socket formation. The radially outwardly extending flange and radially inwardly extending flange are typically connected by a generally tubular portion which can have a larger diameter portion for accommodating a pipe seal and a smaller diameter portion at the axially inner end of the socket. The pallets are usually formed from pressed steel.

In use, the tubular core and sleeve are assembled together with the pallet on a moulding machine and a concrete mix is then poured into the annular space between the inner tubular core and the outer tubular sleeve.

During and after the introduction of the concrete mix, the mould is vibrated to assist settling of the concrete. The upper mould member, which is in the form of a plunger, is then rammed into the top of the mould to further compact the concrete and to form the spigot end shape of the pipe. The upper mould member is left in place for a predetermined period, usually about one and a half minutes, and is then removed. The inner tubular core and outer tubular sleeve are then removed sequentially to leave the unsupported concrete pipe resting on the pallet which is then carefully removed from the moulding machine. The pipe remains on the pallet until the concrete has set fully.

Where the pipe is to be provided with a sealing ring anchored into the concrete in its socket end, the sealing ring is placed about the circumference of the tubular portion of the pallet referred to above before assembly of the mould, the leading edge or front face of the sealing member being fitted closely against the surface of the pallet in such a way as to control the position of the seal in the vertical plane and to ensure parallelism of the seal underface with the tapered surface of the pallet. A removable supporting ring, which is usually formed from a deformable plastics material, and which assists in maintaining the seal in position, is then placed axially behind the sealing member. A gap is left between the sealing member and the outwardly extending flange of the pallet. After the concrete has hardened, and the pallet has been removed from the pipe, the removable support member behind the seal is removed from the pipe socket to leave an annular space into which the seal can deform when a spigot end of the pipe is inserted into the socket.

It will be appreciated from the foregoing description that whereas the upper mould member and the tubular core and tubular sleeve are removed immediately after moulding, the pallet cannot be removed until the concrete has set. This means that in practice, although a pipe manufacturer would need only one or a small number of tubular cores, outer sleeves and upper mould members, a large number of pallets are generally required because of the extended times taken for the concrete to set fully and harden. For large batch production of concrete pipes, hundreds of pallets may be required.

The steel pressing machinery required to make the pallets is generally very expensive and consequently tends to be rather uncommon.

Consequently, concrete pipe manufacturers wishing to change the profiles of the pipe sockets, which in turn requires modification of the profiles of the pallets, are frequently faced with making a potentially huge investment in new pressing machinery in order to create the large numbers of pallets necessary for the batch production of concrete pipes. This in general has had the effect of holding back development of improved joints for concrete pipes.

The present invention sets out to overcome or at least alleviate this problem by providing a means of modifying existing pallets thereby avoiding the need to have large numbers of new pallets fabricated every time the socket design is changed.

The invention achieves this object by providing a pallet which is formed in at least two parts. The first part is an annular mould element corresponding generally to a pallet of the type used for creating smooth walled sockets, whilst the second mould element is an annular support which is secured to the radially outer surface within the concave annular recess defined by the radially outwardly extending flange and the tubular portion of the mould element. By changing the profile of the relatively inexpensive second mould element, it is possible to use a single pressing to create a large number of different socket profiles for concrete pipes.

Accordingly, the invention provides a pallet for shaping and supporting an inner surface of a socket end of a concrete pipe during a moulding operation; the pallet comprising: (i) a first annular mould element; the first annular mould element having a radially outwardly extending first flange portion for supporting an outer axial face of the socket end; a radially inwardly extending second flange portion for supporting an inner axial face of the socket end; and a tubular portion connecting the first and second flange portions; the first flange portion being linked to the tubular portion by a radiussed wall portion, the radially outer surface of the radiussed wall portion defining an annular concave region; and (ii) a separately formed second annular mould element disposed about the circumference of the first annular mould element and secured within the annular concave region thereof; the second annular mould element having a radially outwardly facing circumferentially extending concave surface for supporting a radiussed radially inner edge of the socket end, and a radially inwardly inclined surface axially inwardly of the concave surface for supporting a leading edge of a sealing member to be moulded into the socket end.

The first annular mould element is typically formed from pressed metal, for example from pressed steel, in known fashion. The second annular mould element can be formed from a metal such as steel, or from a polymeric material. Where the second annular mould element is formed from a polymeric material, the material can be for example a crosslinked or thermosetting resin such as an epoxy resin. The resin can advantageously contain fillers and additives for improving the hardness and abrasion resistance characteristics of the resin.

The tubular portion of the first annular element preferably has an axially outermost enlarged diameter portion and an axially innermost reduced diameter portion, the enlarged diameter portion and reduced diameter portion being linked by a radially inclined wall portion. The enlarged diameter portion and/or the reduced diameter portion may each taper slightly in an axially inwards direction.

The second annular mould element has a radially inwardly facing convex surface which has a curvature complementary to the curvature of the annular concave region on the first annular mould element. The radially outwardly facing surface of the second annular mould element has a circumferentially extending concave surface and a radially inwardly inclined surface as defined hereinabove. The circumferentially extending concave surface and the radially inwardly inclined surface can be connected by a generally cylindrical portion. The cylindrical portion may taper in an axially inwards direction; for example the surface of the cylindrical portion may be at an angle of 0.5 to 50 with respect to the axis of the pipe, more usually about 2.5 to 3.50, for example approximately 30.

The radially inwardly inclined surface will usually present an angle of up to about 750 with respect to the axis of the pipe, more usually less than 600, for example 30 to 550, and in particular 35 to 450.

In a further aspect, the invention provides a method of moulding a socket end of a concrete pipe using a pallet as hereinbefore defined.

The invention will now be illustrated by reference to the specific embodiment shown in the accompanying drawings of which: Figure 1 is a partial sectional elevation through a pallet according to one embodiment of the invention; Figure 2 is a partial sectional elevation through a socket end of a concrete pipe and pallet; and Figure 3 is a partial sectional elevation through a concrete pipe socket end having a moulded-in seal and formed using the pallet shown in Figures 1 and 2.

Referring now to the drawings, Figure 2 illustrates the socket end of a concrete pipe supported by a pallet according to one embodiment of the invention. The pallet, generally designated by the numeral 2 comprises a first annular mould element 4 and a second annular mould element 6. First annular mould element 4 is formed from pressed steel and has a radially outwardly extending first flange portion 8 for supporting the outer axial face A of the socket end of the pipe. A radially inwardly extending second flange portion 10 of annular mould element 4 is arranged to support an axial inner face B of the socket end of the pipe. The radially outwardly extending first flange portion 8 and the radially inwardly extending second flange portion 10 are connected by tubular portion 12. Tubular portion 1 2 has an enlarged diameter section 14 and a reduced diameter section 16, the enlarged diameter section 14 and reduced diameter section 16 being linked by radially inwardly inclined section 18. Both the enlarged diameter and reduced diameter portions 14 and 1 6 taper slightly in an axial inwards direction, the angle of taper being of the order of about 1 to 50, for example approximately 3.50.

The radially outwardly extending first flange portion 8 has, at its outer extremity, an annular rim 20 which extends in a direction axially away from the tubular portion 1 4. Annular rim 20 serves to strengthen the flange portion against deformation when the concrete pipe is resting on the pallet.

Connecting the radially outwardly extending first flange portion 8 and the tubular portion 14 is a radiussed wall portion 22. The radially outer surface 24 of the radiussed wall portion defines an annular concave region in which is disposed the second annular mould element 6.

Second annular mould element 6 has a radially inner surface 26 having a curvature corresponding to the curvature of surface 24. On its radially outwardly facing surface, second mould element 6 has a circumferentially extending concave surface 28 which supports the inner edge C of the socket. Concave surface 28 extends into a generally tubular section 30, the walls of which are inclined slightly in a radially inwards direction by approximately 2.5 to 3.5 with respect to the axis of the pipe.

Tubular portion 30 in turn extends into radially inwardly inclined portion 32 which in this embodiment presents an angle of approximately 40 to 45 with respect to the axis of the pipe. Radially inwardly inclined surface 32 in use abuts against a sealing member S.

In use, sealing ring S is stretched about mould member 2 so that the leading edge S1 abuts against surface 32.

Disposed axially behind sealing member S is removable supporting member R which in this embodiment is formed from an extruded flexible polymer material such as ethylene propylene diene monomer (EPDM) or styrene butadiene rubber (SBR). The main body portion S2 of the sealing member extends radially outwardly with respect to the supporting member R, the rear portion S3 of the sealing member overlying the supporting member.

Once the pallet and associated seal and supporting member have been fitted together, the resulting assembly is assembled together with the other mould components on a pipe making machine and used to form a cast concrete pipe produced in conventional fashion. After the concrete has been compacted in the mould, the various components of the mould, with the exception of the pallet and supporting member, are withdrawn, and the pipe is allowed to harden. The pallet and removable supporting member R are then removed. The result is a pipe having a socket end with an anchored in seal as shown in Figure 3.

An advantage of the pallet of the present invention is that the first annular mould element can be adapted to provide any one of a large number of different socket profiles simply by varying the profile of the second annular mould element. Thus the need to use expensive and relatively scarce large scale metal pressing machinery to create the large number of new pressings required each time a new socket profile is introduced is avoided.

It will readily be recognised that numerous modifications and alterations may be made to the mould member shown in the accompanying drawings without departing from the principles underlying this invention. All such modifications and alterations are intended to be embraced by this Application.

Claims

1. A pallet for shaping and supporting an inner surface of a socket end of a concrete pipe during a moulding operation; the pallet comprising: (i) a first annular mould element; the first annular mould element having a radially outwardly extending first flange portion for supporting an outer axial face of the socket end; a radially inwardly extending second flange portion for supporting an inner axial face of the socket end; and a tubular portion connecting the first and second flange portions; the first flange portion being linked to the tubular portion by a radiussed wall portion, the radially outer surface of the radiussed wall portion defining an annular concave region; and (ii) a separately formed second annular mould element disposed about the circumference of the first annular mould element and secured within the annular concave region thereof; the second annular mould element having a radially outwardly facing circumferentially extending concave surface for supporting a radiussed radially inner edge of the socket end, and a radially inwardly inclined surface axially inwardly of the concave surface for supporting a leading edge of a sealing member to be moulded into the socket end.

2. A pallet according to claim 1 wherein the first annular mould element is formed from pressed metal.

3. A pallet according to claim 1 or claim 2 wherein the second -annular mould element is formed from a metal or from a polymeric material.

4. A pallet according to claim 3 wherein the second annular mould element is formed from a polymeric material which is a crosslinked or thermosetting resin.

5. A pallet according to claim 4 wherein the polymeric material is an epoxy resin.

6. A pallet according to claim 4 or claim 5 wherein the resin contains fillers and additives for improving the hardness and abrasion resistance characteristics thereof.

7. A pallet according to any one of the preceding claims wherein the tubular portion of the first annular element has an axially outermost enlarged diameter portion and an axially innermost reduced diameter portion, the enlarged diameter portion and reduced diameter portion being linked by a radially inclined wall portion.

8. A pallet according to claim 7 wherein the enlarged diameter portion and/or the reduced diameter portion each taper slightly in an axially inwards direction.

9. A pallet according to any one of the preceding claims wherein the second annular mould element has a radially inwardly facing convex surface which has a curvature complementary to the curvature of the annular concave region on the first annular mould element.

1 0. A pallet according to any one of the preceding claims wherein the circumferentially extending concave surface and radially inwardly inclined surface of the second annular mould element are connected by a generally cylindrical portion.

11. A pallet according to claim 10 wherein the cylindrical portion tapers in an axially inwards direction.

1 2. A pallet substantially as described herein with reference to the accompanying drawings.

1 3. A method of moulding a socket end of a concrete pipe using a pallet as defined in any one of the preceding claims.