Valve

Abstract

A bi-injection moulded self-closing valve assembly is described. The assembly comprises a valve overmoulded on an insert. The overmoulded valve is injected using side gating of the mould.

Claims

1. A self-closing valve assembly comprising a valve overmoulded on an insert, in which the insert is formed by lateral injection, and in which overmoulded valve is injected by: generally central injection; off-centre injection; or lateral injection.

2. An assembly as claimed in claim 1, in which the insert includes a side wall and the injection point is located on one end of the side wall.

3. An assembly as claimed in claim 1, in which the valve includes a side wall and the injection point is located on one end of the side wall.

4. An assembly as claimed in claim 1, in which the valve includes a valve head and the injection point in located generally centrally on the head.

5. An assembly as claimed in claim 1, in which the valve includes a valve head in which one or more slit lines are to be formed, and in which the valve injection point is located away from the slitting line/s.

6. An assembly as claimed in claim 1, in which the insert is a retaining ring.

7. An assembly as claimed in claim 1, in which the valve is formed from a TPE material.

8. An assembly as claimed in claim 1, in which the insert is formed from polypropylene.

9. An assembly as claimed in claim 1, comprising a side gated polypropylene ring and a side gated TPE valve.

10. An assembly as claimed in claim 1, comprising a side gated polypropylene ring and a centre gated TPE valve.

11. An assembly as claimed in claim 1, comprising a side gated polypropylene ring and an off-centre gated TPE valve.

12. An assembly as claimed in claim 1, in which the valve comprises an injection moulded body formed from a TPE material, the injection moulded body includes a peripheral sidewall and a central valve head, in which the injection gate for the body is formed away from the centre of the valve head.

13. An assembly as claimed in claim 12, in which the injection gate is formed in the peripheral sidewall.

14. An assembly as claimed in claim 1, comprising a self-closing valve and an outer retaining ring, the sub-assembly is formed by a bi-injection moulding process, the ring is injected using a side gated injection process and the valve is injected using a side gated injection process.

15-20. (canceled)

21. A method of forming a valve sub-assembly according to claim 1, comprising the steps of injection moulding the insert using a lateral gate and overmoulding the valve using a lateral gate.

22. A method as claimed in claim 21, further comprising the step of slitting the valve, in which the slit/s are formed so as not to coincide with an injection gate vestige thereon.

23. A self-closing valve comprising an injection moulded body formed from a TPE material, the injection moulded body includes a peripheral sidewall and a central valve head, in which the injection gate for the body is formed away from the centre of the valve head.

24. A method of forming a self-closing valve according to claim 22, comprising the step of injection moulding the valve with an off-centre injection gate.

25. A method as claimed in claim 24, further comprising the step of slitting the valve, in which the slit/s are formed so as not to coincide with an injection gate vestige thereon.

Description

[0063] FIG. 1 shows a self-closing valve sub-assembly, comprising a self-closing valve and an outer retaining ring. The sub-assembly is formed by a bi-injection moulding process.

[0064] FIG. 2A shows the self-closing valve, which in this embodiment is formed from a thermoplastic elastomer (TPE) material. The valve includes a peripheral wall and a concave central valve head. The wall and valve head are joined by a connecting wall, which in this embodiment can function as a hinge to allow the valve head to lift and possibly invert during use. Silts (for example two slits in the form of a cross) may be provided generally centrally on the valve head.

[0065] FIG. 2B shows the valve retaining assembly/device, which in this embodiment is formed from polypropylene. The device comprises a bead for snap-fitting the device into a closure.

[0066] The device (valve plus ring) is shown in FIG. 2C. It is formed separately from a closure and also from a container.

[0067] FIGS. 3 and 4 shows a closure showing the valve with ring inside a closure for use in cosmetic and/or food containers, for example. The valve component (valve plus ring) is fitted into a generally disc-like top plate which itself is then received (e.g. clipped/snapped) into the base of a closure.

[0068] The top plate component is shown separate from the closure in FIGS. 5 and 6. The underside of the lid of the closure includes a domed projection which is shaped to correspond to the concave shape of the valve head, which ensures a good seal when the lid is closed.

[0069] In other embodiments (not shown) the top plate is formed integrally with the closure base.

[0070] The closure therefore includes a TPE valve overmoulded on a polypropylene insert. In this embodiment a side gated polypropylene ring and a side gated TPE valve is provided.

[0071] This embodiment combines a TPE valve design and a valve sub-assembly (VSA) design, obtained through overmoulding.

[0072] The ring and/or outer ring may be combined with the top seal area between valve/closure.

[0073] Design features may be included to ensure we do not have a weld line on the valve headplate.

[0074] In this embodiment this is combined with a top seal area between valve/closure.

[0075] In this embodiment there are no weld lines on the valve headplate.

[0076] The insert includes closure retention features and the system relies on two seals working in unison: vertical compression onto TPE; and annual PP interference.

[0077] In some embodiments the head sleeve hinge the interference to the closure retention form provides horizontal pressure to aid slit closing, increasing the seal quality.

[0078] Results Part 1: FIGS. 7 to 57

[0079] The results show an analysis of the injection of a TPE valve overmolded on an insert in PP, with two gate locations tested for the TPE valve and its influence on injection conditions. The calculations are made with an isotherm mould setting. Warpage and stress results are given assuming a perfect PP geometry without shrinkages, because that is the only way to get the stress tensor in TPE part.

[0080] Shown in the drawings is the seal element the part in which is the TPE valve built in, by 2K injection.

[0081] Overmoulding material: TPE Thermolast K TF3 ATL (Kraiburg TPE GmbH)

[0082] Insert Material: PP Moplen HP50IL (Basel) Polyolefins Europe)

[0083] The PP insert is injected in 0.2 s, at 230° C. in a mould at 30° C. Lateral injection has been validated. A weld line is created in opposite area to the gate. Specific venting could be needed in ends of fillings. Pressure in cavity is about 70 bars. Most massive area could include a risk of sink marks/void bubbles due to skin solidification before it. The packing pressure can't be transmitted as long as possible in this massive area. Homogenising thicknesses is recommended for some embodiments.

[0084] The TPE overmoulding is also injected in 0.2 s, at 200° C. in a mould at 30° C. A lateral and centred injection have been tried and presented in the figures. Shear rate calculated at gate is under the limit preconized in Moldfow database with a gate 00.6 mm and 0.2 s of injection time. Injecting slower could lead to amplify hesitation effects and creates an air trap.

[0085] Pressure in cavity at switchover is about 25 to 35 bars depending of gate location used. Injecting in centre area limit the packing transmission all around the part while lateral injection permits to have a better control of packing all around the part but slightly less packing in central area. This could lead to sink marks/void bubbles in most massive areas depending of gate location. Part warpage, in terms of flatness, is quite similar for the values but appears more regular with lateral injection. A better control of packing and shrinkages should be obtained with lateral injection because we have a better control of packing all around the part. Stress tensor analyse doesn't shows significative differences in terms of values and direction.

[0086] Results 2: FIGS. 58 to 112

[0087] To analyse the injection of a TPE valve overmolded on an insert in PP, in order to test two gate locations for TPE and its influence. The calculations are made with an isotherm mould setting. Warpage & stress results are given assuming a perfect PP geometry without shrinkages, because that's the only way to get the stress tensor in TPE part in calculations with Moldflow software.

[0088] Overmoulding material: TPE Thermolast K TF3 ATL (Kraiburg TPE GmbH)

[0089] Insert Material: PP Moplen HP501 L (Basel) Polyolefins Europe)

[0090] Both PP and TPE are injected in 0.5 s in a mould at 30° C. This injection time has been chosen to limit shear rate at gate and to have an overview of the results with realistic injection (injecting with lower injection time than 0.5 s would imply to know the press injection inertia with precision). Injecting in 0.2 s doesn't modify significatively the flowfront pattern and air trap issue seen with the lateral injection. Pressure in the cavity at switchover are similar with both centred & lateral injection, about 25 to 30 bars in cavity. Cantered injection permits to obtain a balanced filling without weld lines/air trap while lateral injection presents hesitation effects due to part thicknesses and gate location out of part symmetry axis. The air trap created with lateral injection is quite important and lead to different problems such flowfront speed variation, flow acceleration at end of filling on air trap location.

[0091] Injecting by part centre permits to have a correct packing of part centre but the part perimeter which is thickest is less packed and could be present sink marks/void bubbles risks. Lateral injection presents the opposite problem with limited packing of part centre, where the cutting operation will be done in the process after injection.

[0092] Both injections present globally homogeneous shrinkages excepting massive areas far from the gate. Part warpage calculated is similar in both case with low values (less than 0.05 mm). Seeing the stress results calculated in the part, using low packing pressure is recommended in order to limit stress tensor value in the TPE part.

[0093] Comparing both stress tensor direction with each gate location lead to the conclusion that stress tensor main direction is more homogeneous with a central injection than with a lateral one. For some embodiments it may be preferable to inject the part with a central gate to avoid air trap/weld line issue, and to have more homogeneous stress tensor direction. In other embodiments it may be preferable to inject the part with an off-centre gate to avoid the problem of slit line/s coinciding with a gate vestige.

[0094] The current plan is to off centre and direct feed the TPE and to side gate the PP. The benefits of side gating over centre gating are shown. With central injection, the maintenance of more massive areas at the periphery is limited.

[0095] In some embodiments modifying the part design by thickness homogenization may help to have more homogeneous volumetric shrinkages and less sink marks risks in most massive area on part perimeter with the central injection. A calculation could be done to validate possible geometry optimizations (based on part solidification analyse, meaning thicknesses could be optimize with less differential thicknesses and a thinner perimeter area).

[0096] If the thicknesses can be homogenised, compaction may be better.

[0097] The comparison between the two threshold positions clearly shows that the exchange is healthier.

[0098] The lateral injection may create an air occlusion, differential orientations of the main directions of the stress tensor, a sub-compaction of the centre.

[0099] A centre gate may lead to slitting quality issues as you may then be slitting through the gate vestige (which can vary in size and regularity from mould cavity to mould cavity and over time), so side gating can have advantages.

[0100] In some embodiment side gating does not generate internal material stresses which would lead to other issues.

[0101] Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiments shown and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.