AU2020264368B2

AU2020264368B2 - Edge forming in thermoplastics

Info

Publication number: AU2020264368B2
Application number: AU2020264368A
Authority: AU
Inventors: Helan Mo
Original assignee: Able High Int Ltd
Current assignee: Able High International Ltd
Priority date: 2016-09-16
Filing date: 2020-11-06
Publication date: 2023-02-23
Anticipated expiration: 2036-09-16
Also published as: AU2023203118A1; AU2016228295B2; AU2020264368A1; AU2016228295A1

Abstract

with Figure 4 A process for forming a rolled edge in a thermoplastic tray where, in a mould at the position illustrated at 26 the tray has a preformed edge section 27 where the edge section 27 has been set with a slight inclination biasing it towards a mould seat section at 21 whereby the mould seat section is a continuous groove running around the inside of a female mould part 18. At position 27 the mould part 18 which has been heated to a temperature of between 80 degrees celsius and 130 degrees celsius (depending on the thickness of the tray 10 material) the edge 27 will soften around the periphery of the tray 10 and after a few seconds a male part 19 will be timed to push the tray down in the female part until it reaches the location at 28 whereby it will hold momentarily. The terminal edge 17 has by this time started to curl under. This time delay permits additional heat transfer further in from the edge 17, then the male part pushes the tray further into the female mould where again it is held momentarily at the location 29 which again permits heat to be transferred further in from edge 17 while at all times causing the marginal edge section to curl up and then finally when in register with the groove 21 the bottom of the male part at 30 remaining in register with the top of the flange 15 presses the rim down onto the groove 21 whereupon the heated rounded section 16 comes in contact with a lower temperature section 20 which is set about 15 degrees celsius to 30 degrees celsius to cool the rim. 27 Yr24° 221

Description

27 Yr24°

EDGE FORMING IN THERMOPLASTICS TECHNICAL FIELD

[0001] THIS INVENTION relates to edge forming in thermoplastics and in particular to a rolled edge formed by a process applied to an edge in a mould and in particular but not limited to forming an edge of partially completed plastics product.

BACKGROUND

[0002] Edge forming in thermoplastics usually results in a sidewall having a rim comprising an outward flange and a return flange ending in a sheer edge just below the outward flange. Since the sheer edge is usually cut in a die to remove the finished product from a continuous sheet this edge can be relatively sharp. There are plastics products that have an edge which does not have this relatively sharp aspect. It is acknowledged herein that efforts have been made to form a rolled type of edge.

[0003] The following US patents were located in a post-invention search and the full disclosure of these patents is incorporated herein in their entirety and provide useful technical detail in relation to the present invention. These documents are not considered common general knowledge anywhere. US3947205; US8083887; US8920892.

[0004] As will be noted there is provided edge forming that provides a rolled edge in a mould. An object of the present invention is to provide a useful alternative to any known methods for forming any product and a novel tray product produced by any method.

OUTLINE

[0005] A method is described herein as applicable to a tray but other products may be produced using this method. This method may be applied to produce any product suited to that method. Therefore a further object is to provide a product having a thermoformed edge according to the methods and processes described herein. A tray having a rolled edge is not shown in the prior art of record which are not applicable to a tray, consequently applicant is the first to provide a rolled edge in a tray, the tray is therefore novel and inventive in its own right independent of the method, the method being a preferred way of making the tray.

[0006] Accordingly, in one broad aspect there is a provided a method for forming an edge in thin thermoplastic sheet material in a mould having relatively movable male and female parts, the female part having a rolled edge form at the end of an edge shaping surface and the male part being adapted to aid the positioning of the edge against the edge shaping surface.

[0007] In another aspect the invention comprises a method for forming a rolled edge in a marginal edge section of thin thermoplastic, in a mould having an edge form at the end of an edge shaping surface, the method comprising the steps of:

(a) heating the marginal edge section while progressively shaping the heated edge section as it closes toward the edge form; and

(b) closing the edge onto the edge form to form a rolled edge.

[0008] Preferably, the method includes the additional step of pre-forming the edge with a bias toward the edge form. The preformed edge can simply be a marginal flange formed around the periphery of the partial product.

[0009] Preferably, the method comprises progressively shaping the edge in a stepwise fashion. The stepwise fashion typically comprises of applying heat to the marginal edge for a set time at a first position, causing the partially shaped edge to be displaced from the first position to at least one other position, holding the partially shaped edge in the other position for a set time and eventually further displacing the further partially shaped edge to a final position at the edge form. Preferably the formed edge is a rim and the method includes forming an outward flange with a terminal edge and progressively rolling the terminally edge under the flange to produce a rolled over return so that the terminal edge is tucked under the flange. Preferably, the method includes a final press step by reason of the application of an applied force to the flange against the edge form to close the terminal edge against an underside of the flange.

[0010] In another aspect there is provided a tray of thermoplastics having a rim comprising a rolled edge, the rolled edge being rolled under. Preferably, the rim has an outward flange and a rolled over return so that the terminal edge is tucked under the flange. The tray is preferably made according to one of the methods described in the preceding paragraphs. Typically, the flange is substantially flat and the return together with the flange forms a hollow rim. In one form the hollow rim is a half circle in section. In another the hollow rim is a teardrop in section. Preferably, the flange terminates at an inward juncture of the flange with a side wall of the tray and the rolled edge has a terminal edge which runs along or adjacent to the said juncture.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order that the present invention may be more readily put into practice and be understood references made to the accompanying drawings which illustrate preferred embodiments of the invention and wherein:

Figures 1 to 3 are respective plan, end and rim sectional views of a tray with an edge formed using the teachings of the present invention; Figure 4 is a schematic drawing illustrating operation of a mould to produce a rolled edge of the type depicted in Figure 3; Figures 5, 6 and 7 are non limiting examples of some of the types of the rolled edges that may be accomplished using the teachings of the present invention; and Figure 8 is a drawing showing one application of the present invention to the rim of a tray for packing produce with a cling film wrap.

METHODOFPERFORMANCE

[0012] Referring to the drawings and initially to Figure 1 to 3 there is illustrated a tray 10 having an outer rim 11 and a base 12 and various base ribbing and protrusions 13, 14 with the rim 11 having an outward flange 15 and a rolled over return 16 so that the terminal edge 17 is tucked under the flange 15 as shown in Figure 3. The rolled edge is effectively in the form of a semi circle by reason of the application of an applied force to the flange against a rim form in a mould and the process by which this is formed is illustrated in greater details in Figure 4. The flange may be 2-10 mm wide in material that are .25 -1mm thick. Typical plastics are PVC, PET, PP PS and PC but any plastic that can be formed by the process may be used.

[0013] Referring now to Figure 4 there is illustrated a mould comprising a female mould part and a male mould portion 19 with the female mould part having a bottom section 20 with an edge form 21 at the end of a sloping inside wall 22. This arrangement is for forming a tray so it will be appreciated that although a section is being shown the mould matches the tray so the edge form extends right around the mould.

[0014] Thus the drawing of Figure 4 shows a section through part of the female mould but it will be appreciated that this extends completely around the mould so that a container or tray 10 of the type illustrated in Figure 1 may be manually placed in the mouth 23 of the female mould part 18 in proper alignment and then the male mould part 19 may push down vertically in the direction of 24 until the tray 10 as the case may be, part of which is shown in Figure 4 is pushed down into the position illustrated at 25 whereby the rim 11 is duly formed. The male part would typically travel on two or more guide rails.

[0015] Now as shown in Figure 4 the process is stepwise insofar at the position illustrated at 26 the tray has a preformed edge section 27 where the edge section 27 has been set with a slight inclination biasing it towards the mould seat section at 21 whereby the mould seat section is a continuous groove running around the inside of the female mould part 18. As can be seen from position 27 the mould part 18 which has been heated to a temperature of between 80 degrees celsius and 130 degrees celsius (depending on the thickness of the tray 10 material) the edge 27 will soften around the periphery of the tray 10 and after a few seconds the male part 19 will be timed to push the tray down in the female part until it reaches the location at 28 whereby it will hold momentarily. The terminal edge 17 has by this time started to curl under. This time delay permits additional heat transfer further in from the edge 17, then the male part pushes the tray further into the female mould where again it is held momentarily at the location 29 which again permits heat to be transferred further in from edge 17 while at all times causing the marginal edge section to curl up and then finally when in register with the groove 21 the bottom of the male part at 30 remaining in register with the top of the flange 15 presses the rim down onto the groove 21 whereupon the heated rounded section 16 comes in contact with a lower temperature section 20 which is set about 15 degrees celsius to 30 degrees celsius to cool the rim.

[0016] The male part 19 is then retracted and a second piston or ejection mechanism is used to push the tray up and back to the mouth 13 whereby it can be manually removed.

[0017] It will be appreciated that depending upon the shape of the groove 21 which comprises the edge form that various rims may be achieved in these shown in Figures 5 through 7. It will be further appreciated that again depending on the type thermoplastic, thickness, width of the flange, amount of bias on the preform, shape of the mould and that these variables will change the process parameters in terms of timing, time delay at each step, number of steps, so these all fall within the scope of the invention.

[0018] The present invention has particular application as illustrated in Figure 1 part shown in Figure 8 where the tray 10 in this case carries produce such a minced meat and this is covered with a cling wrap film 32 which wraps around the entirety of the minced meat and the container including roll formed edge of the rim at 11 and it will be appreciated that the froll formed edge as prepared according to present invention has little interference with the operation of the cling film 32 insofar there are no sharp edges to cut through the cling film.

[0019] Whilst the above has been given byway of illustrative example many variations and modifications will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set out in the appended claims.

Claims

1. A method for forming an edge in a tray of thin thermoplastic sheet material in a mould having relatively movable male and female parts, the female part having a rolled edge form comprising a mould seat section at the end of an edge shaping surface and the male part being adapted to aid the positioning against the edge shaping surface, characterised in that the tray is provided with a preformed peripheral edge section, the preformed edge section being set with a slight inclination biassing it towards the mould seat section whereby the mould seat section is a continuous groove running around the inside of the female mould part, the female mould part being heated to soften the preformed edge section around the periphery of the tray and after softening, the male part is used to push the tray down in the female part whereby the preformed edge section begins to curl under and by reason of momentary delays to permit additional heat transfer, as the male part pushes the tray further into the female mould part further curling forms a rim of the tray from the preformed edge section, which when in register with the groove, the male part presses the rim down onto the groove whereupon the rim comes in contact with a lower temperature section of the female mould part to cool the rim.

2. The method of claim 1 wherein the preformed peripheral edge section is a preformed marginal flange formed around the periphery of the tray.

3. The method of any one of the preceding claims wherein the method comprises progressively shaping the edge in a stepwise fashion.

4. The method of any one of claims 1-3 wherein the method comprises progressively shaping the edge section in a stepwise fashion, the stepwise fashion comprises of applying heat to the edge section for a set time at a first position then moving it to partially shape it, causing the partially shaped edge to be displaced from the first position to at least one other position, holding the partially shaped edge in the other position for a set time and eventually further displacing the further partially shaped edge to a final position at the edge shaping surface.

5. The method of any one of the preceding claims wherein the method includes a final press step where an applied force is used to press the rim.

6. A tray of thermoplastics made according to the method of claim 1 which has the rim has an outward flange and a rolled over return with a terminal edge which is tucked in under the flange.

7. A tray of thermoplastics made according to the method of claim 1 the rim comprises a flange which is substantially flat and a return which together with the flange forms a hollow rim.

8. A tray of thermoplastics made according to the method of claim 1 where the rim comprises a flange which is substantially flat and a return which together with the flange forms a hollow rim which is a half circle in section.

9. A tray of thermoplastics made according to the method of claim 1 wherein the rim has an outward flange and a rolled over return with a terminal edge which is tucked in under the flange, the flange terminates at an inward juncture of the flange with a side wall of the tray and the terminal edge runs along or adjacent to the said juncture.