WO2018053577A1

WO2018053577A1 - Vacuum mould apparatus

Info

Publication number: WO2018053577A1
Application number: PCT/AU2017/051000
Authority: WO
Inventors: Christopher Mervyn Bovell
Original assignee: Christopher Mervyn Bovell
Priority date: 2016-09-20
Filing date: 2017-09-14
Publication date: 2018-03-29

Abstract

The present invention relates to a vacuum mould apparatus comprising an inner wall and an outer wall which are spaced to define a cavity therebetween; a floor and a ceiling connected to at least the outer wall to thereby define a vacuum chamber, the vacuum chamber comprising an air inlet and an air outlet; a join formed by end faces of the inner and outer walls to allow access to the vacuum chamber; and a channel formed in at least one of the end faces, the channel having one or more apertures formed therein which are continuous with the cavity. The present invention enables the production of foam products under vacuum while minimising or reducing the incidence of the ingress of air into the vacuum chamber in which the foam product is forming.

Description

VACUUM MOULD APPARATUS

FIELD OF THE INVENTION

[0001 ] The invention relates to the field of apparatus for vacuum moulding. More particularly, this invention relates to an apparatus for vacuum forming a foam article and a method of forming such articles using same.

BACKGROUND TO THE INVENTION

[0002] Any reference to background art herein is not to be construed as an admission that such art constitutes common general knowledge in Australia or elsewhere.

[0003] Foam blocks or buns are produced for a range of applications including use as mattresses, cushions, pillows, seats and in a variety of sporting applications. One of the most common foam products is polyurethane foam which is formed by the reaction of an isocyanate with a polyol.

[0004] The characteristics, including the shape and density, of the foam article can be controlled during the manufacturing process in a number of ways. This is challenging not least because the foam forming reaction between the isocyanate and polyol is extremely fast, in the order of seconds, and so specialised systems must be put in place.

[0005] To control the density of a foam product it is common in the industry to employ blowing agents which are typically volatile organic solvents such as dichloromethane (DCM). However, chlorinated solvents such as DCM are undesirable due to their negative environmental impact when they are ultimately released into the atmosphere.

[0006] A vacuum can, in theory, be used to control the density of the foam without the need for the addition of blowing agents. In practice this approach has encountered a number of difficulties resulting in it not being taken up by the foam producing industry. Particularly, the rising foam must be contained within a mould to give the desired shape to the end product. This mould must be capable of subsequently being opened to allow quick and easy removal of the foam block or bun. This requires that the mould be openable, and hence have a join, along a substantial portion of its walls, for example along its entire length so that it opens in two halves. This join is a potential inlet for air and it is found that, once the mould is placed under vacuum, even small quantities of air which enter through the join in the mould can cause deep tracts and damage into the core of the foam product due to the accelerating effect on the air by the vacuum. This renders the foam product defective and often unsuitable for use.

[0007] This problem is particularly troublesome in, although not unique to, the formation of cylindrical foam buns due to additional challenges in forming an airtight seal on a cylindrical mould. One approach in the industry, when manufacturing cylindrical foam buns, to form a standard rectangular foam block and then machine peel this to provide the desired shape. This results in wastage of over a third of the formed foam. Other approaches involve the use of extremely large vacuum chambers requiring significant capital expenditure and large amounts of factory space and still do not provide for the desired degree of simplicity and control.

[0008] There is a need for a vacuum mould apparatus which enables the production of foam products under vacuum while minimising or reducing the incidence of the ingress of air into the vacuum chamber in which the foam product is forming.

OBJECT OF THE INVENTION

[0009] It is an aim of this invention to provide for a vacuum mould apparatus and method of using same which overcomes or ameliorates one or more of the disadvantages or problems described above, or which at least provides a useful alternative.

[0010] Other preferred objects of the present invention will become apparent from the following description. SUMMARY OF INVENTION

[001 1 ] According to a first aspect of the invention, there is provided a vacuum mould apparatus comprising:

(a) an inner wall and an outer wall which are spaced to define a cavity therebetween;

(b) a floor and a ceiling connected to at least the outer wall to thereby define a vacuum chamber, the vacuum chamber comprising an air inlet and an air outlet;

(c) a join formed by end faces of the inner and outer walls to allow access to the vacuum chamber; and

(d) a channel formed in at least one of the end faces, the channel having one or more apertures formed therein which are continuous with the cavity.

[0012] Preferably, the inner wall is absent adjacent the ceiling such that the cavity and the vacuum chamber are continuous in that region.

[0013] Suitably, the channel extends along the majority of the length of at least one of the end faces and is provided with a plurality of apertures which are continuous with the cavity. Preferably, the channel extends substantially along the length of at least one of the end faces.

[0014] The end faces of the inner and outer walls defining the channel are preferably provided with a resilient seal.

[0015] Preferably, the vacuum chamber is generally cylindrical in shape.

[0016] The vacuum mould apparatus may further comprise one or more base apertures which are formed on the inner wall adjacent the floor and are continuous with the cavity. [0017] The vacuum mould apparatus may further comprise a removable base which is adapted to sit on the floor such that it substantially covers the base apertures.

[0018] In one embodiment, the vacuum mould apparatus may be provided in two separate sections.

[0019] The two sections will come together at a contact face thereof and at least one of which contact faces will be provided with a channel having one or more apertures formed therein which are continuous with the cavity.

[0020] According to a second aspect of the invention there is provided a method of forming a foam product under vacuum including the steps of:

(a) providing a vacuum mould having an inner wall and an outer wall, which are spaced to define a cavity therebetween, and a floor and a ceiling connected to at least the outer wall to thereby define a vacuum chamber, the vacuum chamber comprising an air inlet and an air outlet and a join formed by end faces of the inner and outer walls, a channel formed in at least one of the end faces, the channel having one or more apertures formed therein which are continuous with the cavity;

(b) mixing the foam forming reagents in a mixer to form a foam mixture and initiate the foam forming reaction;

(c) introducing the foam mixture into the vacuum chamber;

(d) closing the vacuum chamber and introducing a vacuum into the vacuum chamber;

(e) removing air which penetrates the join before it enters the foam mixture by virtue of an active vacuum generated along the channel, to thereby form a foam product under vacuum. [0021 ] The various features and embodiments of the present invention, referred to in individual sections above apply, as appropriate, to other sections, mutatis mutandis. Consequently features specified in one section may be combined with features specified in other sections as appropriate.

[0022] Further features and advantages of the present invention will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order that the invention may be readily understood and put into practical effect, preferred embodiments will now be described by way of example with reference to the accompanying figures wherein:

[0024] FIG 1 is a perspective view of the exterior of one embodiment of a vacuum mould apparatus;

[0025] FIG 2 is perspective view of a portion of the vacuum mould apparatus of FIG 1 with a portion of the inner wall removed;

[0026] FIG 3 is an exploded view of an end face and contact face of the portion of the vacuum mould apparatus shown in FIG 2;

[0027] FIG 4 is a plan view of a lower section of the vacuum mould apparatus of FIG 1 when opened; and

[0028] FIG 5 is a front perspective view of the vacuum mould apparatus of FIG 1 when opened.

DETAILED DESCRIPTION OF THE DRAWINGS

[0029] In this patent specification, adjectives such as first and second, left and right, front and back, top and bottom, etc., are used solely to define one element or method step from another element or method step without necessarily requiring a specific relative position or sequence that is described by the adjectives. [0030] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as would be commonly understood by those of ordinary skill in the art to which this invention belongs.

[0031 ] In a first aspect of the invention, there is provided a vacuum mould apparatus comprising:

[0032] FIG 1 is a perspective view of the exterior of one embodiment of such a vacuum mould apparatus 100. The vacuum mould apparatus 100, in the embodiment shown, is formed in two separable sections being a lower mould section 200 and an upper mould section 300. The vacuum mould apparatus 100 is provided with a vacuum system 400 including an air outlet 405 which is connected to a vacuum pump (not shown) for removal of air from the vacuum mould apparatus 100 and an air inlet 410 to reintroduce air. A control lever 415 is provided to allow control over the air inlet 410 manually and a vacuum gauge 420 allows the internal vacuum of the vacuum mould apparatus 100 to be monitored.

[0033] In the embodiment shown in FIG 1 , the upper mould section 300 has been elevated by means of chains 500, which would be attached to a mechanical lifting system such as a hydraulic lift (not shown), and lowered down to abut onto, and form a connection 600 with, the lower mould section 200. The lower mould section 200 and upper mould section 300 are openable along a vertical join line 750. In FIG 1 the join 750 is closed and held tightly shut by a series of fasteners 700 which, in the embodiment shown, are toggle or buckle latches 700.

[0034] The lower mould section 200 may be provided on wheels or otherwise be transportable such that it can be moved underneath the mixing chamber in which the foam forming reagents are mixed. After the fast introduction of the foam forming mixture into the lower mould section 200 through its open upper extent the lower mould section 200 is immediately transported to the appropriate location where the upper mould section 300 is then lowered down onto the lower mould section 200 until the two are connected to form the complete vacuum mould apparatus 100 shown. The vacuum pump can then be engaged to assist with formation of a suitable low density foam product.

[0035] Turning now to FIGs 2 to 4, which show select portions of the vacuum mould apparatus 100 in more detail, it is apparent that the vacuum mould apparatus 100 comprises an outer wall 205 and an inner wall 210 which are spaced to define a cavity 215. FIG 2 shows a section of the inner wall 210 removed so as to reveal the cavity 215. The outer wall 205 and inner wall 210 are maintained separate by elongate braces 220 which connect with both of the outer wall 205 and inner wall 210. The elongate braces 220 also provide structural strength to the vacuum mould apparatus 100. The elongate braces 220 are provided with a series of apertures 225 formed therein which prevent the cavity from being broken up into discrete sections by the elongate braces 220. The apertures 225 allow the cavity to be continuous throughout its extent.

[0036] It will be appreciated that although in the embodiment shown the elongate braces 220 run vertically along the cavity other arrangements may be equally effective and are contemplated by the present design. For example, the elongate braces 220 may not be single continuous pieces or may be provided running horizontally between the outer wall 205 and inner wall 210 instead of vertically. The outer wall 205 and inner wall 210 may be constructed from plywood although any material which can be formed into the desired shape may be acceptable.

[0037] In FIG 2 one half of the lower mould section 200 has been removed for clarity's sake and so an end face of the lower mould section 200 which would engage with a complimentary end face of the removed half can be seen. This end face is shown in more detail in FIG 3 and is seen to comprise an inner wall end face 230 and an outer wall end face 235 which define, between them, a recessed channel 240 which is recessed with respect to the inner wall end face 230 and the outer wall end face 235. The channel 240 is provided with further apertures 225 formed therethrough along its extent which open into the cavity 215. This arrangement of recessed channel 240 with apertures 225 formed therein is referred to herein as an active vacuum seal arrangement.

[0038] As the embodiment shown in the figures is a two piece vacuum mould apparatus 100 the channel 240 formed in the end face of the lower mould section 200 continues onto and along a contact face of the lower mould section 200 (to be part of connection 600) formed by inner wall contact face 245 and outer wall contact face 250 and is also, in this region, provided with apertures 225 which extend through the channel 240 and into the cavity 215.

[0039] At least the outer wall end face 235 and outer wall contact face 250 are provided with a resilient material to form a resilient seal which better resists the ingress of air. The resilient material may be a foam or rubber material which aids in forming a better seal with the corresponding face when the vacuum mould apparatus 100 is fully assembled, closed and in operation. Such materials are known in the art.

[0040] It will be appreciated that in an embodiment wherein the vacuum mould apparatus 100 is a one piece design with a separate inlet for the foam forming mixture then the connection 600 would not be present and hence the connecting face with the inner wall contact face 245 and outer wall contact face 250 and the portion of the channel 240 lying therebetween would not be present and the channel 240 would only be formed on an end face forming the vertical join 750 by which the vacuum mould apparatus 100 is opened for removal of the foam product.

[0041 ] At least one end face of each join 750 may be provided with the channel 240 and apertures 225. For example, in FIG 2 where only one half of the lower mould section 200 is shown the channel 240 and apertures 225 are only shown in the left most end face. This would mean that the complimentary end face of the half of the lower mould section 200 not shown which would abut with the right most end face of that half shown may be provided with the channel 240 and apertures 225. Alternatively, the lower mould section 200 and upper mould section 300 may be designed such that, although they have a vertical join down their length to allow them to be opened for removal of the foam bun, the outer wall is actually continuous around the region directly opposite the join 750 around which the walls pivot when opening such that air cannot penetrate that region and hence the channel 240 and apertures 225 seal arrangement is not required.

[0042] A floor 255 is shown in FIG 2 which can receive a removable base 800 which is typically a smooth padded structure upon which the foam bun will form. The inner wall 210 is provided with a plurality of base apertures 260 around its lower extent adjacent to the floor 255. In operation, the removable base 800 will sit in close contact with the inner wall 210 and has a height such that the base apertures 260 are substantially obscured. This results in the removable base 800 being drawn down tightly onto the floor 255 when the vacuum is engaged to thereby form an effective seal around the lower extent of the vacuum chamber. This means that a channel 240 and aperture 225 arrangement, as seen on at least one of the end faces forming the join 750, is not strictly required along the faces of the floor 255 which come together to form the complete floor 255. However, a channel 240 and apertures 225 may be provided in this region by way of an additional safeguard.

[0043] FIG 4 shows the lower mould section 200 when viewed from above. In this view the provision of the channel 240 and apertures 225 formed therein is clearly visible around the extent of the contact face of the lower mould section 200 which will form part of connection 600. As discussed above, wherever there is a join, seal or break in the outer wall 205 through which air may potentially enter then at least one of the faces making up that join, seal or break may be provided with the channel 240 and apertures 225 arrangement to form an active vacuum seal when the vacuum pump is engaged. This means that although in the embodiment shown in FIG 4 the contact face of the lower mould section 200 is shown as having this active vacuum seal arrangement, the arrangement could just as easily be formed only on the complimentary contact face of upper mould section 300. The end face or contact face which is not provided with the active vacuum seal arrangement may simply be a smooth fully formed surface or may instead be provided with a series of apertures 225 continuous with the cavity 215 but without the presence of a channel 240. Alternatively, both end or contact faces may be provided with the active vacuum seal arrangement.

[0044] FIG 5 is a front perspective view of the vacuum mould apparatus of FIG 1 when opened. The upper mould section 300 is seen to be provided with a ceiling 370 which is connected to the elongate braces 220 and the outer wall of the upper mould section 305 such that when the lower mould section 200 and upper mould section 300 are connected then the outer wall 205, 305 (in part), inner wall 210, 310, floor 255 and ceiling 370 define the vacuum chamber. The inner wall 310 does not extend all the way to the ceiling 370 such that the cavity and the vacuum chamber are continuous in that region. This results in a relatively small open region 320 where the elongate braces 220 and outer wall 305 adjacent the ceiling 370 are observable from the interior of the vacuum chamber. The result of this is that air located within the cavity 215 is pulled towards the ceiling 370 and when it reaches the open region 320 where the inner wall 310 is absent it is drawn in to the vacuum chamber and then out through the air outlet 405.

[0045] The air outlet 405 and air inlet 410 both open into the ceiling 370, although other arrangements which don't directly impact on the forming foam product may be considered. Where they open into the vacuum chamber they are each shielded by a cover 330 which, in its simplest form, may be a piece of plywood supported by legs extending from the ceiling 370 into the vacuum chamber to sit substantially parallel with the ceiling a short distance below the opening of the air outlet 405 or inlet 410. This means that the force of air being drawn out of the air outlet 405 or of its return through the air inlet 410 is not focused on one area of the forming or formed foam product which could result in localised damage or deformation. The covers 330 serve to dissipate this force. The covers 330 and the open region 320 of the vacuum chamber which is not provided with the inner wall 210 are located at a high enough vertical position such that the forming foam will not contact these areas. The height which a particular volume of foam can attain under specific vacuum conditions can be easily ascertained by one of skill in the art through a series of simple test runs. The apertures 225 and 325 are shown running along the right hand end face of the lower mould section and upper mould section 300 but could just as easily be provided on both end faces simultaneously, or the right hand side end face of one and left hand side end face of the other and vice versa.

[0046] In a second aspect of the invention a method of forming a foam product under vacuum and employing the vacuum mould apparatus 100, as previously described, is provided wherein the foam forming reagents are first mixed in a specialised mixing chamber. Once thorough mixing occurs the foam forming reactions are underway and there is a limited period of time before the foam rises and sets. It is only during this short period that its shape, density and other characteristics can be modified. The mixing chamber may be designed to dump the foam mixture into the lower mould section 200 which can be wheeled in to place beneath the mixing chamber. The lower mould section 200 will have its end faces in abutment to form a part of join 750 and the buckle latches 700 will be fastened i.e. the lower mould section 200 is in the 'closed' position. It will also already have the removable base 800 in place on the floor 255.

[0047] The lower mould section 200 is then moved to a suitable location and the upper mould section 300 is lowered on top such that the exposed contact faces thereof abut to form transverse connection 600. The upper mould section 300 will also be in its 'closed' position to form the vacuum mould apparatus 100 substantially as shown in FIG 1 . The use of resilient material along all joins along with buckle latches 700 for the join 750 and the weight of the upper mould section 300 bearing down for the connection 600 mean that a reasonable seal is generated at all joins and connections to prevent the ingress of air when the vacuum is engaged.

[0048] The vacuum pump is immediately activated to draw air from the vacuum chamber until a pressure of approximately -15 to -25 KPa is reached. The exact vacuum pressure employed will depend to some extent on the type of foam being produced and the density required of the final foam product but around -20 KPa is typical to produce a relatively low density polyurethane foam bun. When the vacuum reaches this level the active vacuum seal arrangements described before comes into play.

[0049] The vacuum is pulled into the vacuum chamber and hence draws the forming foam upwards while it solidifies to create low density foam. Due to the region of the vacuum chamber adjacent the ceiling 370 from which the inner wall 210 is absent the vacuum also extends into the cavity 215. Through the series of apertures formed in the elongate braces 220, one or both of the end faces forming the join 750 and one or both of the contact faces forming connection 600 the vacuum extends all around the cavity 215 and into the channels 240. The removable base 800 sits in engagement with the base apertures 260 which, due to their opening into the cavity 215, results in a seal forming above the floor 255. [0050] This arrangement ensures that each join, connection and seal is actively exposed to the vacuum pressure. The join in the floor 255 does not necessarily require a channel 240 based active vacuum seal since the removable base 800 forms an effective seal above it. The ceiling 370 sits above the level the foam will rise to and has the vacuum pulling directly from it and so a channel 240 based active vacuum seal arrangement is, again, not required for the join in the ceiling 370 although one may be employed.

[0051 ] The foam will rise under a substantially constant vacuum pressure which can be achieved by monitoring of the vacuum gauge 420 and occasional activation of the control lever 415 to allow an amount of air into the vacuum chamber through the air inlet 410. Alternatively, the vacuum control may be automated with the gauge 420 and control lever 415 effectively being replaced by computer software.

[0052] If an imperfect seal has been formed along the connection 600 of the lower mould section 200 and the upper mould section 300 or of the join 750 formed by the abutment of the end faces then small amounts of air can be drawn in to the vacuum chamber at speed and cause damage to the forming foam if it were not for the provision of the active vacuum seal arrangement. Instead the air will pass across either the outer wall end face 235 or outer wall contact face 250 and be drawn into the channel 240 due to the active vacuum pulling along the channel 240. This results in the air immediately being drawn along the channel 240 to the nearest aperture 225 at which point it is dispersed throughout the cavity 215 and eventually drawn up to the open region 320 where the inner wall 310 is absent at which point the air enters the vacuum chamber proper, but only at that point immediately adjacent the ceiling where no foam is forming, and is drawn from there straight into the air outlet 405 and on to the vacuum pump.

[0053] In this manner air is prevented from passing through a join 750 or connection 600 directly into the vacuum chamber at a point where the foam product is actively forming. The provision of a channel 240 which is continuous with the cavity 215 which is itself maintained under vacuum by being continuous with the upper extent of the vacuum chamber proper acts as an active trap for incoming air and ensures the inner wall seal is not breached.

[0054] When the foam has solidified and the final product is achieved the vacuum is released, the buckle latches 700 can be quickly undone and the end faces of the join 750 separated. It may be convenient to first raise the upper mould section 300 to either be completely removed from or at least sit slightly above the lower mould section 200 to allow for easier opening. The foam bun, which sits on the removable base 800, can then be accessed. For example, the forks of a forklift truck may be inserted under the removable base 800 which is then removed with the foam bun on top.

[0055] The present invention provides a number of advantages over the prior art which have not been hitherto available. The use of environmentally damaging blowing agents can be avoided by the use of the present vacuum mould apparatus 100 which, advantageously, acts simultaneously as a mould to shape the forming foam and also as a vacuum apparatus to assist in drawing the foam upwards to achieve an appropriately low density. The chances of damage to the foam bun are greatly reduced by the provision of the active seal arrangements described herein and so wastage is greatly reduced. Finally, although the active vacuum seal arrangement can be applied to any shape of mould it has particular advantage when used in a cylindrical mould, as described herein. This is because, due to the cylindrical shape it has always been particularly challenging to adequately seal such a mould along its length such that air cannot enter. For this reason a typical industry approach was formerly to produce a rectangular foam block in a standard mould with sealed flat lid and then machine peel this block to give a cylindrical foam bun. The fact that over a third of the foam was wasted in such an approach was accepted as a necessary attrition. Further approaches have required the construction of massive pressurised chambers which need special handling and infrastructure to implement them into a factory setting and significantly increase the capital cost. The present invention allows cylindrical foam buns to be produced in a short time frame with no additional shaping steps and with little or no wastage.

[0056] The above description of various embodiments of the present invention is provided for purposes of description to one of ordinary skill in the related art. It is not intended to be exhaustive or to limit the invention to a single disclosed embodiment. As mentioned above, numerous alternatives and variations to the present invention will be apparent to those skilled in the art of the above teaching. Accordingly, while some alternative embodiments have been discussed specifically, other embodiments will be apparent or relatively easily developed by those of ordinary skill in the art. Accordingly, this patent specification is intended to embrace all alternatives, modifications and variations of the present invention that have been discussed herein, and other embodiments that fall within the spirit and scope of the above described invention.

[0057] In the claims which follow and in the preceding description of the invention, except where the context clearly requires otherwise due to express language or necessary implication, the word "comprise", or variations thereof including "comprises" or "comprising", is used in an inclusive sense, that is, to specify the presence of the stated integers but without precluding the presence or addition of further integers in one or more embodiments of the invention.

Claims

1 . A vacuum mould apparatus comprising:

2. The vacuum mould apparatus of claim 1 , wherein the inner wall does not extend to the ceiling such that the cavity and the vacuum chamber are continuous in that region.

3. The vacuum mould apparatus of claim 1 or claim 2, wherein the channel extends along the majority of the length of at least one of the end faces and is provided with a plurality of apertures which are continuous with the cavity.

4. The vacuum mould apparatus of claim 3, wherein the channel extends substantially along the length of at least one of the end faces.

5. The vacuum mould apparatus of any one of the preceding claims, wherein the end faces of the inner and outer walls defining the channel are provided with a resilient seal.

6. The vacuum mould apparatus of any one of the preceding claims, wherein the vacuum chamber is generally cylindrical in shape.

7. The vacuum mould apparatus of any one of the preceding claims further comprising one or more base apertures which are formed on the inner wall adjacent the floor and are continuous with the cavity.

8. The vacuum mould apparatus of claim 7 further comprising a removable base which is adapted to sit on the floor such that it substantially covers the base apertures.

9. The vacuum mould apparatus of any one of the preceding claims, wherein the vacuum mould apparatus is provided in two separate sections.

10. The vacuum mould apparatus of claim 9, wherein the two sections come together at a contact face thereof and at least one of which contact faces will be provided with a channel having one or more apertures formed therein which are continuous with the cavity.

1 1 . The vacuum mould apparatus of any one of the preceding claims, wherein the air outlet is connected to a vacuum pump.

12. A method of forming a foam product under vacuum including the steps of:

(b) mixing foam forming reagents in a mixer to form a foam mixture and initiate the foam forming reaction; and

(c) introducing the foam mixture into the vacuum chamber; (d) sealing the vacuum chamber and introducing a vacuum into the vacuum chamber; and

(e) removing air which penetrates the join before it enters the foam mixture by virtue of an active vacuum generated along the channel, to thereby form a foam product under vacuum.

13. The method of claim 12 performed using the apparatus of any one of claim 1 to claim 1 1 .

14. A foam product produced by the method of claim 12 or claim 13.