GB2307202A

GB2307202A - A mould capable of releasing moulded article

Info

Publication number: GB2307202A
Application number: GB9623906A
Authority: GB
Inventors: Brian Robert Jones
Original assignee: NUMOLD
Current assignee: NUMOLD
Priority date: 1995-11-18
Filing date: 1996-11-18
Publication date: 1997-05-21
Anticipated expiration: 2016-11-18
Also published as: GB2307202B; GB9623906D0; GB9523653D0

Abstract

A plastics mould for moulding elongate articles, such as concrete fence posts, comprises an elongate base 12 and two spaced side walls 10 which are co-extensive and integral with the base. The side walls diverge as they extend upwardly from the opposite longitudinal side edges 15 of the base 12, and are formed with inward longitudinal projections 13 to form longitudinal grooves in the sides of the moulded article. The base 12 is resiliently flexible and is curved upwardly so that it becomes flattened and stressed when the side walls 10 are moved towards one another and are held in their operative moulding position. When the side walls are subsequently released they tend to spring apart, due to the stress in the base 12, thus facilitating removal of the moulded article from the mould.

Description

"A Mould for Moulding Elongate Articles" The invention relates to moulds for moulding elongate articles and is particularly, but not exclusively, applicable to moulds for moulding concrete fence posts of the kind where the post is generally rectangular in cross-section with longitudinal grooves running vertically along two opposite faces of the fence post to receive the edges of vertical panels which extend between adjacent posts.

Such fence posts are commonly moulded from reinforced concrete in an opentopped mould comprising an elongate base and two spaced side walls co-extensive with the base and upstanding from the opposite longitudinal side edges thereof. The side walls are formed with longitudinally extending inward projections to form the longitudinal grooves in the side faces of the fence post.

In order to be able to remove the moulded fence post from the mould it is of course necessary to disengage the projections on the side walls from the grooves in the post, and various methods have been employed for achieving this. For example, the lower edges of the side walls may be connected by hinges to the side edges of the base so that the side walls may be pivoted away from the moulded article. However, in the case where the side walls and base are formed from sheet metal this has the disadvantage that conventional hinges between the side walls and the base will allow liquid to leak from the mould and also such hinged moulds are comparatively costly.

Accordingly, as an alternative, one-piece moulds have been made from resiliently flexible material, such as plastics material, to prevent such leakage. In one form of such mould, as shown in British Patent Specification No. 2208623, the natural resilient flexibility of the material of the mould is relied on to allow the side walls to be moved apart and out of engagement with the sides of the moulded article. With such arrangement the side walls of the mould have to be held apart, against their resilience, while the fence post is removed from the mould and this may be inconvenient.

In an alternative arrangement, as shown in British Patent Specification No.

2254582 the mould is again a one-piece plastics mould and the junction between each side wall and the base is pre-formed with a scored fold line so as to provide a longitudinal hinge so that the side walls can pivot about the side edges of the base. This may allow the side walls to remain in their opened position during removal of the moulded article, but the scoring of the material may significantly weaken the mould along the junctions between the side walls and the base so that splitting may occur along this junction as a result of the repeated stressing of the hinge in prolonged use. Also, release fluid used in the moulding process can so affect the thinned region of the mould, due to the scoring, as to cause distortion of the mould.

The present invention provides an improved form of mould for slotted fence posts and other elongate articles which may overcome the above-mentioned disadvantages of the prior art arrangements. In a preferred embodiment of the invention the side walls ofthe mould tend to spring to their open position without requiring to be held in that position, thus facilitating removal of the article from the mould, while at the same time the structure ofthe mould is such that there are no areas of thinning, or other regions of concentrated stress, which may result in distortion or structural failure of any part of the mould.

According to the invention there is provided a mould for moulding elongate articles comprising an elongate base and two spaced side walls co-extensive with the base and upstanding from the opposite longitudinal side edges thereof, the base being deformable in cross-section in a manner to allow movement of the side walls towards and away from one another to permit release of a moulded article from the mould.

Since the movement of the side walls is allowed by deformation of the base, the junction between each side wall and the base may be strong and comparatively rigid. It is therefore completely waterproof and not liable to distort or split with prolonged use of the mould. Also, the mould can be formed from materials which are not flexible enough to provide sufficient opening of the mould by flexing of the junctions alone.

Preferably the base of the mould is flexible, said movement of the side walls towards and away from one another being permitted by flexing of the base across the width thereof.

The side walls may be integral with the base, and are preferably fixed relative to the longitudinal side edges of the base, the movement of the side walls towards and away from one another being permitted by deformation of a portion of the base which is spaced inwardly away from both side walls.

In the case where the base of the mould is flexible it may be flexible between a first position where the base is substantially flat and the side walls are in a moulding orientation, and a second position where the side walls are in a separated releasing orientation and the base, as a result of the movement apart of the side walls, curves upwardly between the side walls. Preferably the base of the mould is resiliently flexible and adopts said second position when unstressed.

In the case where the side walls are integral with the base and the lower portions of the side walls extend at an angle to the outer portions of the base, said angle preferably remains the same in both the first and second positions of the base of the mould. For example, said angle may remain at substantially 90" In any of the arrangements referred to above, the side walls may be formed with inwardly and longitudinally extending projections in which case the outward movement permitted by deformation ofthe base should be sufficient for said projections to clear the moulded article.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which: Figure 1 is a cross-section through an elongate slotted fence post mould in accordance with the present invention; Figure 2 shows the mould in use to mould a fence post, and Figures 36 are cross-sections, corresponding to Figure 1, through further forms of mould in accordance with the invention.

Referring to Figure 1, the mould is formed from plastics material and comprises two spaced side walls 10 which are co-extensive with a base wall 12 and are upstanding from the longitudinal side edges of the base wall.

The mould may be of any required length (a convenient length is 3m) and may be extruded, vacuum formed, or injection moulded. The mould may be formed from any suitable plastics material such as ABS, HDPE or polypropylene.

Each side wall 10 is formed with a longitudinal channel 13 which forms a longitudinal inward projection into the interior of the mould cavity. The upper edge of each side wall is provided with an outwardly turned longitudinal flange 14.

The base wall 12 ofthe mould is upwardly curved in the unstressed condition, and at each junction 15 between the longitudinal side edge portion 16 of the base 12 and the adjacent lower portion of the side wall 10 the base and side wall are arranged at an angle of90" to each other. In the case where the width of the base wall is about 1 OOmm, the base wall may extend at 90" from each junction for a distance of about 1 Omm before beginning to curve.

The side walls 10 of the mould are of substantially constant thickness, such thickness being maintained around each junction 15. However, the base wall 12 becomes slightly thinner as it extends inwardly from each junction 15 so as to increase its flexibility in regions away from the side walls 10.

In use, as shown in Figure 2, the mould is introduced into a rigid channel-section former 17 having a horizontal base 18 and side walls 19 extending at right angles to the base 18. The former may be conveniently made from wood, or metal.

The distance between the side walls 19 of the former is the same as the length of the base wall 12 of the mould. Consequently, as the mould is introduced into the former 17 the side walls 10 of the mould are pushed together, such movement causing flattening of the base wall 12 of the mould so that the mould fits inside the former 17, as shown in Figure 2, with the base wall 12 resting flat on the bottom wall 18 of the former and the side walls 10 bearing against the side walls 19 of the former. The flanges 14 hook over the upper edges of the side walls 19 of the former.

It will be noted that the angle between the base portion 16 and side wall 10 at each junction 15 is 90" in the unstressed condition of the mould, as shown in Figure 1, and is also 90" in the operative condition of the mould as shown in Figure 2. It will therefore be appreciated that the bringing of the side walls 10 to the operative condition is solely as a result of flexing of the part of the base wall 12 which is spaced inwardly from the side walls 10 and that no flexing stress is therefore imparted to each junction 15. Accordingly, there is no concentrated stress at the junctions which might, over prolonged use, lead to splitting of the mould at those junctions.

The interior of the mould is then filled with concrete, usually with reinforcing rods, as indicated at 20 in Figure 2.

When the concrete has set, the fence post, together with the mould is lifted from the former 17 and the side walls 10 of the mould are pulled apart so that the moulded fence post can easily be removed from the mould. The initial movement of the side walls 10 away from the sides ofthe moulded fence post is accompanied by very slight flexing ofthe mould at the junctions 15. As soon as the mould begins to separate from the post, however, the necessary further movement of the sides 10 away from post is permitted solely by the upward flexing of the base wall 12 of the mould. This permits the sides 10 to be separated from the post by a sufficient distance to allow the post to be lifted from the mould. This allows the mould to be manufactured from materials where the flexing of the junctions 15 alone would not allow the sides 10 to be separated by a sufficient extent.

Figures 1 and 2 show a mould for the manufacture of a basic concrete fence post formed with continuous longitudinal grooves in two opposite faces thereof. However, similar mould constructions can also be used for the manufacture of modified versions of this basic post structure, as will now be described.

In some cases it may be desirable for the longitudinal groove in the finished post to be formed with a moulded nib extending transversely across the groove partway along its length. For example, such a nib may be required as support for a gravel board. In order to form the nib, therefore, each longitudinal channel 13 of the mould is formed, at the appropriate position partway along its length, with a short re-entrant channel extending transversely of the main channel 13. The re-entrant transverse channel may extend to the full depth of the main channel 13, or only a part of its depth.

Figures 3, 4 and 5 are similar views to Figure 1 showing moulds, incorporating the invention, but for moulding different types of fence post.

Figure 3 shows a mould for a post for use at the end of a run of fencing, the post accordingly having only a single channel 21 for moulding a single groove in one face of the fence post, the other three faces being plain.

Figure 4 shows a mould for a corner post for connecting two fencing panels at right angles. In this case only one side wall of the mould is formed with a longitudinal channel 22, but the curved base 23 of the mould is also formed with a longitudinal channel 24.

Figure 5 shows a mould for a fence post for use at a three-way junction where a straight row of fencing panels is met by a further fencing panel at right angles. In this case, therefore, the opposite sides of the mould are formed with channels 25 while the curved bottom wall 26 of the mould is also formed with a channel 27.

Although the moulds described above are specifically for the moulding of elongate slotted concrete fence posts, it will be appreciated that the principle of the invention is applicable to many other types of open-topped mould to facilitate separation of the moulded article from the mould after manufacture.

Figure 6 shows, for example, a mould incorporating the invention but suitable for moulding a narrow wall panel from concrete or other suitable material. In this case the side walls 28 of the mould are formed, at least on their inner faces, with a configured surface to impart a textured surface to each side of the finished wall panel. For example, the intemal configuration of the side walls may represent the surface configuration of a natural wooden panel, and for this purpose the plastics side walls of the mould may be themselves moulded in contact with a natural wood panel in order to achieve the required configuration. The configured surfaces of the mould might also represent stonework or any other natural surface. Alternatively, the surfaces may be configured with a designed geometric pattern or the like.

In each case, however, the base wall 29 of the mould is curved in similar fashion to the arrangement of Figure 1, so that the side walls of the mould may readily spring apart to allow easy release of the moulded product.

Claims

1. A mould for moulding elongate articles comprising an elongate base and two spaced side walls co-extensive with the base and upstanding from the opposite longitudinal side edges thereof, the base being deformable in cross-section in a manner to allow movement of the side walls towards and away from one another to permit release of a moulded article from the mould.

2. A mould according to Claim 1, wherein the base of the mould is flexible, said movement ofthe side walls towards and away from one another being permitted by flexing of the base across the width thereof.

3. A mould according to Claim 2, wherein the side walls are integral with the base.

4. A mould according to Claim 3, wherein the side walls are fixed relative to the longitudinal side edges of the base, the movement of the side walls towards and away from one another being permitted by deformation of a portion of the base which is spaced inwardly away from both side walls.

5. A mould according to any of Claims 2 to 4, wherein the base of the mould is flexible between a first position where the base is substantially flat and the side walls are in a moulding orientation, and a second position where the side walls are in a separated releasing orientation and the base, as a result of the movement apart of the side walls, curves upwardly between the side walls.

6. A mould according to Claim 5, wherein the base of the mould is resiliently flexible and adopts said second position when unstressed.

7. A mould according to any of the preceding claims, wherein the base of the mould becomes thinner as it extends away from the side walls.

8. A mould according to any of Claims 2 to 7, wherein the side walls are integral with the base and the lower portions of the side walls extend at an angle to the outer portions ofthe base, and said angle remains substantially the same in both the first and second positions of the base of the mould.

9. A mould according to Claim 8, wherein said angle remains at substantially 90".

10. A mould according to any of the preceding claims, wherein at least one of the side walls is formed with an inwardly extending projection and the outward movement permitted by deformation of the base is sufficient for said projection to clear the moulded article.

11. A mould according to Claim 10, wherein said projection extends inwardly and longitudinally ofthe side wall ofthe mould, so as to form a longitudinally extending groove in the side of the moulded article.

12. A mould according to Claim 10 or Claim 9, wherein inward projections are provided on both side walls of the mould.

13. A mould according to any of the preceding claims wherein the base of the mould is formed with an inwardly extending projection.

14. A mould according to any of the preceding claims, wherein the inwardly facing surfaces of said side walls of the mould are configured to provide textured surfaces on the exterior of the moulded article.

15. A mould for moulding elongate articles, substantially as hereinbefore described with reference to any of Figures I to 6 of the accompanying drawings.

16. A moulded article when moulded using a mould according to any of the preceding claims.