GB2302668A

GB2302668A - A hinged mould and a method for moulding an article

Info

Publication number: GB2302668A
Application number: GB9613640A
Authority: GB
Inventors: Colm Vincent Concannon; Patricia Nora Concannon; Andrew Bernard Menzies; John Francis Concannon; Patrick Joseph Moran; Sean Gerard Dunleavy; Cathal Gerard Fitzpatrick; Brendan Joseph Morrin
Original assignee: Rodicon Ltd
Current assignee: Rodicon Ltd
Priority date: 1995-06-29
Filing date: 1996-06-28
Publication date: 1997-01-29
Anticipated expiration: 2016-06-28
Also published as: GB9613640D0; GB2302668B; IE950479A1

Abstract

A mould (1) for moulding an animal drinking trough (2) figure 11 (not shown) using a rotational moulding process comprises a top mating part (8) and a bottom mating part (9) which are hingedly connected by a pair of hinge connections (18), and which are hingeable from a closed position whereby the mating parts (8) and (9) define a hollow interior region (10) within which the trough (2) is moulded to an open position for facilitating removal of the trough (2) from the hollow interior region (10). Toggle clamps (24) spaced apart around flanges (11) and (12) secure the mating parts (8) and (9) together during moulding. The toggle clamps (24) are also provided adjacent to the hinge connections (18). Reinforcing frameworks (31) and (32) reinforce the mould (1), and a mounting frame (36) welded to the reinforcing framework (31) releasably secures the mould (1) to a carrier frame (4) of rotational moulding apparatus.

Description

"A mould and a method for moulding an article" The present invention relates to a mould and a method for moulding a plastics article in a rotational moulding process.

Rotational moulding of plastics articles is well known.

In general, a mould within which the plastics article is formed is mounted on a carrier frame of a rotational moulding apparatus which rotates the mould about two axes perpendicular to each other. The mould, in general, is a two part mould having two mating parts which when secured together in mating engagement define a hollow interior region, which in turn, defines the outer shape of the moulded article. In general, articles which are rotationally moulded are of hollow construction. Plastics material in powder form is placed in the hollow interior region in the mould which is then secured and placed on the carrier frame of the rotational moulding apparatus. The carrier frame rotates the mould about the two perpendicular axes in an oven.The two parts of the mould are of heat conductive material, and heat from the oven is conducted through the mould to the inner surfaces of the mould which define the hollow interior region. As the inner surfaces commence to heat the plastics material in powder form begins to melt and adhere to the inner surfaces of the mould. By rotating the mould about the two perpendicular axes the plastics material is relatively evenly distributed over the entirety of the inner surfaces of the mould.

One problem with such moulds is that the two parts are provided as separate parts which are separated from each other when open, and during moulding are secured together by releasable securing means. Thus on the securing means being released the two parts separate from each other. In many cases, as the parts are being separated the moulded article can fall out of the mould, thus leading to damage of the moulded article. A further problem is that alignment of the two parts of the mould can sometimes be difficult and since the two parts of the mould are separated from each other, other than when secured together, in certain cases, the parts may be incorrectly secured together.

There is therefore a need for a mould which overcomes these problems, and there is a need for a method for rotationally moulding a plastics article which likewise overcomes these problems.

The present invention is directed towards providing such a mould and a method for rotationally moulding a plastics article, and a plastics article formed from the mould and the method.

According to the invention there is provided a mould for use in a rotational moulding process for moulding a plastics article, the mould comprising two mating parts which when secured together define a hollow interior region within which the plastics article is formed, the mating parts defining complementary mating faces which abut each other when the two parts are secured together, and a plurality of securing means spaced apart around the periphery of the mating faces for securing and retaining the mating parts together, wherein the two mating parts are hingedly connected together by at least one hinge connection which defines a hinge axis, and the two mating parts are hingedly moveable about the hinge axis from a closed position with the mating faces abutting each other and forming the hollow interior region to an open position with the two mating parts spaced apart from each other for permitting removal of the plastics article from the hollow interior region, and a securing means is provided relatively close to each hinge connection.

Preferably, the hinge axis lies in the plane of the mating faces when the mating faces are abutting each other and is spaced apart from the respective mating parts for providing clearance when the mating parts are in the open position for facilitating removal of the plastics article from the hollow interior region.

Advantageously, the mating parts are hingedly moveable relative to each other about the hinge axis through an angle of approximately 1800.

Ideally, each hinge connection comprises a pair of hinge members, one hinge member extending from each mould part, and a pivot pin pivotally engages at least one of the hinge members. Preferably, at least two hinge connections are provided, the pivot pins of the respective hinge connections defining a common hinge axis.

In one aspect of the invention, the mating parts are of heat conductive material.

In another aspect of the invention, a reinforcing means is provided on each mating part for reinforcing the respective mating parts. Preferably, the hinge connections extend from the reinforcing means.

In a preferred aspect of the invention, a releasable mounting means is provided on the mould for releasably mounting the mould to a carrier frame of a rotational moulding apparatus.

Preferably, the releasable mounting means comprises a pair of elongated spaced apart side members and at least a pair of spaced apart cross members extending between the side members and defining with the side members an opening for slidably engaging a portion of the carrier framework of the rotational moulding apparatus.

Advantageously, each side member is formed by a member of angle steel, at least one of the cross members extending between and being located substantially in the plane of one of the webs of the respective angle members, and the other of the cross members extending between free edges of the other webs of the respective angle members. Preferably, a pair of cross members extend from the free edges of the web of the respective angle members. Advantageously, a releasable fastening means is provided for fastening the mould to the carrier frame. Ideally, the fastening means comprises a fastener through an opening in one of the cross members for securing the mould to the carrier frame, and preferably, the releasable mounting means is slideably engagable with the carrier frame.

Additionally, the invention comprises a carrier frame for use in a rotational moulding apparatus, the carrier frame comprising a mould according to the invention mounted on the carrier frame.

Further, the invention provides a method for rotationally moulding a plastics article using the mould according to the invention, the method comprising the steps of placing plastics material in powder form from which the article is to be formed in one of the mating parts of the mould with the mating parts open, closing the mating parts of the mould together about the hinge axis, securing the mating parts together in the closed position with the securing means, placing the mould on a carrier frame of a rotational moulding apparatus, positioning the carrier frame with the mould mounted thereon into an oven, rotating the carrier frame in the oven about two rotational axes at right angles to each other for rotating the mould about two perpendicularly disposed axes for dispersing the plastics material onto the inner surface of the mould until the plastics material has melted and is formed on the inner surface of the mould, transferring the carrier frame from the oven to a cooling station, and slowly cooling the mould in the cooling station for solidifying the plastics material, releasing the securing means, hinging the two mating parts of the mould apart into the open position, and removing the moulded article from the mould.

In one aspect of the invention, a portion of an outer surface of the mould is covered by heat insulating material for preventing the transfer of heat to a portion of the inner surface of the mould adjacent to the outer portion covered with the heat insulating material for preventing forming of the plastics material on the said portion of the inner surface of the mould.

In another aspect of the invention, the moulded article is an animal drinking trough.

The invention also provides a plastic article manufactured using the mould according to the invention, and preferably, using the method according to the invention.

The invention will be more clearly understood from the following description of a preferred embodiment thereof which is given by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a mould according to the invention for moulding a plastics article in a rotational moulding process, Fig.2 is a perspective view of the mould of Fig. 1 from a different direction, Fig. 3 is a perspective view of the mould of Fig. 1 illustrated open, Fig. 4 is a plan view of the mould of Fig. 1, Fig. 5 is an underneath plan view of the mould of Fig. 1, Fig. 6 is a cross-sectional end elevational view of the mould of Fig. 1 on the line VI-VI of Fig. 5, Fig. 7 is an enlarged cross-sectional view of a detail of the mould of Fig. 1, Fig. 8 is a perspective view of the mould of Fig. 1 illustrated mounted on a portion of a rotational moulding apparatus, Fig. 9 is an enlarged perspective view of a portion of the view of Fig. 8, Fig. 10 is a cross-sectional side view of a detail of the portion of Fig. 9, and Fig. 11 is a partly cut-away perspective view of an article moulded in the mould of Fig. 1.

Referring to the drawings and initially to Figs. 1 to 7 there is illustrated a mould according to the invention indicated generally by the reference numeral 1 for use in a rotational moulding process also according to the invention for moulding a plastics article. In this case, the mould 1 is suitable for moulding an animal drinking trough 2 of polyethylene plastics material, see Fig. 11. The mould 1 is suitable as will be described below with reference to Figs. 8 to 10 for mounting on a carrier frame 4 of rotational moulding apparatus which is not shown, but will be well known to those skilled in the art. Before describing the mounting of the mould 1 to the carrier frame 4, the mould 1 will first be described in detail.

The mould 1 comprises two mating parts, namely, a top mating part 8 and a bottom mating part 9. The top and bottom mating parts 8 and 9 when secured together define a hollow interior region 10 which defines the outer shape of the trough 2, and within which the trough 2 is moulded using the rotational moulding process. The top mating part 8 and the bottom mating part 9 are each of heat conductive steel plate material and peripheral flanges 11 and 12 extend around the periphery of the top and bottom mating parts 9 and 10, respectively, and define respective mating faces 14 and 15 of the top and bottom mating parts 8 and 9, respectively. When secured together, the mating faces 14 and 15 are aligned with each other and abut each other so that the two mating parts 8 and 9 form the hollow interior region 10.

A pair of hinge connections 18 hingedly connect the top and bottom mating parts 8 and 9 together so that the mating parts 8 and 9 may be hinged from a closed position illustrated in Figs. 1, 2 and 6 forming the hollow interior region 10 to an open position illustrated in Fig. 3 for removal of the moulded trough 2. In this embodiment of the invention the hinge connections 18 are arranged so that the two mating parts 8 and 9 can be hinged through an angle greater than 1800. Each hinge connection 18 comprises a pair of hinge members 19 of steel which extend from the respective top and bottom mating parts 8 and 9. A pivot pin 20 pivotally engages and pivotally connects the hinge members 19 of each hinge connection 18.The hinge members 19 are arranged so that the pivot pins 20 of the hinge connections 18 form a common pivot axis 21 about which the mating parts 8 and 9 are pivotable, so that the top and bottom mating parts 8 and 9 can be hinged well clear of each other for facilitating ease of removal of a moulded trough 2 from the hollow interior region 10. The hinge axis 21 defined by the pivot pins 20 lies in the plane of the mating faces 14 and 15 when the mating parts 8 and 9 are in the closed position, and the hinge axis 21 is well spaced apart from the top and bottom mating parts 8 and 9 for facilitating ease of hinging the mating parts 8 and 9 apart into the open position when a moulded trough is in the hollow interior region 10.

A plurality of securing means for securing the two mating parts 8 and 9 together comprises a plurality of toggle clamps 24 which are spaced apart around the peripheral flanges 11 and 12. In this embodiment of the invention the toggle clamps 24 are mounted on the flange 11 of the top mating part 8, and a catch 25 of each toggle clamp 24 engages a corresponding lug 26 mounted on the flange 12 of the bottom mating part 9.

Such toggle clamps and their operation will be well known to those skilled in the art. The toggle clamps 24 as well as being provided on the side of the mould 1 opposite to the side on which the hinge connections 18 are provided, are also provided on the side of the mould 1, and are located relatively closely to the hinge connections. This ensures that the top and bottom mating parts 8 and 9 are adequately secured together around the entire periphery of the flanges 11 and 12.

A reinforcing means for reinforcing the top and bottom mating parts 8 and 9 comprises a pair of reinforcing frameworks 31 and 32. The reinforcing framework 31 is provided on the top mating part 8, and the reinforcing framework 32 is provided on the bottom mating part 9.

The reinforcing framework 31 is welded to the flange 11 of the top mating part 8, and the hinge members 19 of the top mating part 8 are welded to two members 33 of the reinforcing framework 31. Similarly, the reinforcing framework 32 is welded to the peripheral flange 12 of the bottom mating part 9, and the hinge members 19 of the bottom mating part 9 are welded to members 34 of the reinforcing framework 32.

A releasable mounting means for mounting the mould 1 onto a carrier arm 35 of the carrier frame 4 (see Figs.

7 to 9) of the rotational moulding apparatus (not shown) comprises a mounting frame 36 which is welded to and extends from the reinforcing framework 31 of the top mating part 8. The mounting frame 36 comprises a pair of side members 37 of angle steel which are joined by cross members 38 and 39, and which with the side members 37 define an elongated opening 40 which slidably engages the carrier arm 35 of the carrier frame 4. Fastening means for securing the mounting frame 36 to the carrier arm 35 is provided by a screw 41 which passes through a hole 42 in the cross member 38 and is secured to a corresponding receiving member 43 of the carrier arm 35.

The mould 1 is arranged so that the majority of the trough 2 is formed in the bottom mating part 9, in fact the bottom mating part 9 forms a portion of the trough up to just below a level of a top flange 45 of the trough 2. The flange 45 and the portion of the trough adjacent to the flange 45 is formed in the top mating part 8. Since the portion of the trough 2 within the flange 45 is to be open, a panel 47 of heat insulating material is provided on the top mating part 8 to prevent a portion of an inner surface 49 of the top mating part 8 heating sufficiently to receive and retain melted plastics material. This technique will be known to those skilled in the art. A breathing tube 50 extends through the heat insulating panel 47 and the top mating part 8 for exhausting the hollow interior region 10 to prevent a build-up of pressure in the hollow interior region 10 during moulding.

To mould the trough 2 the inner surfaces of the top and bottom mating parts 8 and 9 which define the hollow interior 10 are initially coated with a release agent to facilitate release of the moulded trough 2 from the mould. The appropriate quantity of polyethylene material in powder form is placed in the hollow interior region 10 of one of the mating parts 8 and 9.

The mating parts 8 and 9 are then hinged into the closed position, and secured together with the toggle clamps 24. The mould 1 is then mounted onto the carrier arm 35 of the carrier frame 4 by engaging the mounting frame 36 onto the carrier arm 35. The mounting frame 36 is secured to the carrier arm 35 by the screw 41.

The mould 1 and the carrier frame 4 are then entered into an oven and the carrier frame 4 is rotated about two axes of rotation perpendicular to each other for likewise rotating the mould 1 about two perpendicular axes. The heat from the oven is transferred through the top and bottom mould parts 8 and 9 thereby causing the polyethylene plastics material powder to melt and adhere to the inner surfaces of the mould 1 to form the trough 2. Due to the fact that the portion 47 of the inner surface of the hollow interior region 10 adjacent the panel 47 does not heat sufficiently for melting the plastics material little if any plastics material adheres to this surface, thereby forming the opening of the trough 2 within the flanges 45.

After a predetermined time in the oven, the plastics material is melted and is evenly distributed over the inner surfaces of the hollow interior region 10. At that stage the carrier frame 4 is removed from the oven, and entered in a cooling station where the mould 1 is slowly cooled to solidify the plastics material within the mould 1. On the mould 1 being sufficiently cooled the toggle clamps 24 are released and the two mating parts 8 and 9 of the mould hinged apart and the moulded trough 2 is removed.

The advantages of the invention are many. By virtue of the fact that the mating parts of the mould are hingedly connected together, when the mould and moulded article within the mould is cooled, the mating parts of the mould may be hinged apart slowly after releasing the toggle clamps, and by hinging the mating parts slowly into the open position, there is no danger of the moulded article falling from the mould, thus avoiding any possible damage to the moulded article.

Another important advantage of the invention is that there is no danger of the mating parts of the mould being mis-aligned when secured together, due to the fact that the two mating parts are hingedly connected together. A further advantage of the invention is provided when the moulds are relatively large and the two parts thus relatively heavy. By virtue of the fact that the two parts are hingedly connected together, one part can readily easily be hinged from the other part without any significant effort or force being required, and furthermore, the weight of the two parts is irrelevant. This is a significant advantage, since in known moulds where the moulds are relatively large, the two parts are relatively heavy, and in general, it requires two people to lift one mould part from the other for separation of the two mould parts for removing the moulded article.Likewise, closing the two mould parts of the mould according to the invention is also a one-person operation.

An advantage of providing the reinforcing framework for reinforcing the mould is that it minimises any danger of the mould going out of shape, and in particular, it reinforces the mating flanges, thereby avoiding bending of the flanges and thus, ensuring a good seal between the mating faces of the mating flanges.

While the mould and method according to the invention have been described for moulding a trough of plastics material, the mould and method may be used for moulding any plastic article of any suitable or desired plastics material which is capable of being rotationally moulded, typically, as well as being suitable for moulding troughs, the mould and method may be used for moulding insert units for forming part of the floor and side wall of jeeps, trailers, and other such vehicles, and indeed, any hollow type article, for example drinking bowls for humans and/or animals, linen trollies, animal hutches, buckets, and any other containers.

In general, it is envisaged that the mould and method will be used for moulding hollow articles only.

Needless to say where the mould is being used for moulding articles of other shape and construction, a mould with the appropriately shaped hollow interior region for forming the article to be moulded will be provided.

While the method according to the invention has been described for use with moulding a trough of polyethylene plastics material, other suitable plastics material may be used, for example, PVC material and the like.

Claims

1. A mould for use in a rotational moulding process for moulding a plastics article, the mould comprising two mating parts which when secured together define a hollow interior region within which the plastics article is formed, the mating parts defining complementary mating faces which abut each other when the two parts are secured together, and a plurality of securing means spaced apart around the periphery of the mating faces for securing and retaining the mating parts together, wherein the two mating parts are hingedly connected together by at least one hinge connection which defines a hinge axis, and the two mating parts are hingedly moveable about the hinge axis from a closed position with the mating faces abutting each other and forming the hollow interior region to an open position with the two mating parts spaced apart from each other for permitting removal of the plastics article from the hollow interior region, and a securing means is provided relatively close to each hinge connection.

2. A mould as claimed in Claim 1 in which the hinge axis lies in the plane of the mating faces when the mating faces are abutting each other and is spaced apart from the respective mating parts for providing clearance when the mating parts are in the open position for facilitating removal of the plastics article from the hollow interior region.

3. A mould as claimed in Claim 1 or 2 in which the mating parts are hingedly moveable relative to each other about the hinge axis through an angle of approximately 1800.

4. A mould as claimed in any preceding claim in which each hinge connection comprises a pair of hinge members, one hinge member extending from each mould part, and a pivot pin pivotally engages at least one of the hinge members.

5. A mould as claimed in Claim 4 in which at least two hinge connections are provided, the pivot pins of the respective hinge connections defining a common hinge axis.

6. A mould as claimed in any preceding claim in which the mating parts are of heat conductive material.

7. A mould as claimed in any preceding claim in which a reinforcing means is provided on each mating part for reinforcing the respective mating parts.

8. A mould as claimed in Claim 7 in which the hinge connections extend from the reinforcing means.

9. A mould as claimed in any preceding claim in which a releasable mounting means is provided on the mould for releasably mounting the mould to a carrier frame of a rotational moulding apparatus.

10. A mould as claimed in Claim 9 in which the releasable mounting means comprises a pair of elongated spaced apart side members and at least a pair of spaced apart cross members extending between the side members and defining with the side members an opening for slidably engaging a portion of the carrier framework of the rotational moulding apparatus.

11. A mould as claimed in Claim 10 in which each side member is formed by a member of angle steel at least one of the cross members extending between and being located substantially in the plane of one of the webs of the respective angle members, and the other of the cross members extending between free edges of the other webs of the respective angle members.

12. A mould as claimed in Claim 11 in which a pair of cross members extend from the free edges of the web of the respective angle members.

13. A mould as claimed in any of Claims 10 to 12 in which a releasable fastening means is provided for fastening the mould to the carrier frame.

14. A mould as claimed in Claim 13 in which the fastening means comprises a fastener through an opening in one of the cross members for securing the mould to the carrier frame.

15. A mould as claimed in any of Claims 9 to 14 in which the releasable mounting means is slideably engagable with the carrier frame.

16. A mould substantially as described herein with reference to and as illustrated in the accompanying drawings.

17. A carrier frame for use in a rotational moulding apparatus, the carrier frame comprising a mould as claimed in any preceding claim mounted on the carrier frame.

18. A method for rotationally moulding a plastics article using the mould as claimed in any preceding claim, the method comprising the steps of placing plastics material in powder form from which the article is to be formed in one of the mating parts of the mould with the mating parts open, closing the mating parts of the mould together about the hinge axis, securing the mating parts together in the closed position with the securing means, placing the mould on a carrier frame of a rotational moulding apparatus, positioning the carrier frame with the mould mounted thereon into an oven, rotating the carrier frame in the oven about two rotational axes at right angles to each other for rotating the mould about two perpendicularly disposed axes for dispersing the plastics material onto the inner surface of the mould until the plastics material has melted and is formed on the inner surface of the mould, transferring the carrier frame from the oven to a cooling station, and slowly cooling the mould in the cooling station for solidifying the plastics material, releasing the securing means, hinging the two mating parts of the mould apart into the open position, and removing the moulded article from the mould.

19. A method as claimed in Claim 18 in which a portion of an outer surface of the mould is covered by heat insulating material for preventing the transfer of heat to a portion of the inner surface of the mould adjacent to the outer portion covered with the heat insulating material for preventing forming of the plastics material on the said portion of the inner surface of the mould.

20. A method as claimed in Claim 18 or 19 in which the moulded article is an animal drinking trough.

21. A method for rotationally moulding a plastics article, the method being substantially as described herein with reference to and as illustrated in the accompanying drawings.

22. A plastics article manufactured using the mould as claimed in any of Claims 1 to 16.

23. A plastics article as claimed in Claim 22 manufactured using the method as claimed in any of Claims 17 to 21.