METHOD AND INSTALLATION FOR THE MANUFACTURE OF CAPSULES

Abstract

Manufacturing capsules, comprising preparing a first and a second capsule element, at least the first element containing a cavity, each element, being provided with a peripheral ring, bringing the elements together, so that the rings are superimposed, placing the two elements between a sonotrode and an anvil, the anvil containing an anvil recess and a striking surface, surrounding the anvil recess, the sonotrode including a sonotrode recess, with the same cross-section as the anvil recess, and a working surface surrounding the sonotrode recess, wherein the striking and working surfaces are configures to come into contact with each other on a working area, extending around the recesses, clamping the rings between the working surface and the striking surface by the proximity of a sonotrode and the anvil, activating the sonotrode and directing the ultrasound towards the anvil, whilst maintaining the clamping action, wherein the rings are detached from the capsule.

Claims

1. A method for the manufacture of capsules, comprising: a) a preparation stage including the preparation of a first and a second capsule element formed from thermoplastic material, at least the first element containing a cavity, each element, being provided with a peripheral ring, b) a stage during which the first and the second elements are brought together, so that the rings are superimposed, c) a placement stage, for the placement of the set of the two elements between a sonotrode and an anvil, the anvil containing an anvil recess and a striking surface, surrounding the anvil recess, the sonotrode including a sonotrode recess, with the same cross-section as the anvil recess, and a working surface surrounding the sonotrode recess, wherein The striking and working surfaces are configured to come into contact with each other on a working area, extending around the recesses, the area having a width of between 0.05 and 1 mm, d) a clamping stage, during which the rings are clamped between the working surface and the striking surface by the proximity of a sonotrode and the anvil, e) a welding stage, during which the sonotrode is activated and directs ultrasound towards the anvil, whilst maintaining the clamping action, until the elements are welded together, and cut-out has been achieved, whereby the rings are detached from the capsule.

2. The method for manufacture in accordance with claim 1, wherein the second element also has a cavity, the cavities having the shape of a semi-sphere, so that they form a capsule in the shape of a ball.

3. The method, in accordance with claim 2, wherein between stages “a” and “b”, preparation and bringing-together, the cavity is filled with a liquid or a solid in fractured form, during a filling stage.

4. The method, in accordance with claim 2, wherein, between stages “a” and “b”, preparation and bringing together, the cavity is filled with a gel, during a filling stage.

5. The method, in accordance with claim 4, wherein the volume of gel deposited in the cavity is greater than the volume of the cavity.

6. The method, in accordance with claim 5, wherein, during stage “b”, the rings are clamped against each other so that excess gel is expelled beyond the rings.

7. The method, in accordance with claim 6, wherein the gel is a paint and the capsule is a paintball.

8. The method, in accordance with claim 7, wherein the width of the working area is between 0.1 and 0.4 mm.

9. The method, in accordance with claim 8, wherein the power of the ultrasound during the welding stage, “e”, increases.

10. The method, in accordance with claim 9, wherein the frequency of the ultrasound is between 25 and 40 kHz.

11. The method, in accordance with claim 10, wherein the rings are provided with retention profiles, during the preparation stage, “a”, wherein the bringing-together stage, “b” is thereby completed by the joining of these retention means, so that the first and the second element are assembled.

12. The method in accordance with claim 11, wherein the first element is taken from a first strip, and the second element is taken from a second strip.

13. The method, in accordance with claim 12, wherein the first element and the second element are made from biodegradable thermoplastic material.

14. Installation for the manufacture of capsules, comprising receptable means for a first and a second capsule element formed from a film made of thermoplastic material, at least the first element containing a cavity, each element being provided with a peripheral ring, means to bring together the first and the second elements in such a way as to superimpose the rings, welding means including a sonotrode, and an anvil, the anvil including an anvil recess and a striking surface surrounding the anvil recess, the sonotrode including a sonotrode recess with the same cross-section as the anvil recess and a working surface surrounding the sonotrode recess, wherein the working and striking surfaces are configured to come into contact with each other on a working area extending around the recesses, the area having a width of between 0.05 and 1 mm, wherein the welding means include a clamping means to clamp the rings between the working surface and the striking surface by the proximity of the sonotrode and the anvil, and a means to generate ultrasound in order to generate ultrasound in the sonotrode, which is directed towards the anvil, the installation putting into practice the method, in accordance with claim 1.

15. The method, in accordance with claim 9, wherein the frequency of the ultrasound is between 30 and 35 kHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention is better understood, and other advantages and specificities will appear clearer, upon reading the following section, which makes references to appended drawings including:

[0033] FIG. 1, a profile diagram of a first and a second thermoplastic film before forming,

[0034] FIG. 2, a similar diagram to FIG. 1, of two elements after the forming stage,

[0035] FIG. 3, showing the filling stage,

[0036] FIG. 4, showing the bringing-together stage, during which the two elements are assembled,

[0037] FIG. 5, showing the two elements being welded together,

[0038] FIG. 6, a detailed view of VI from FIG. 5.

DETAILED DESCRIPTION

[0039] An embodiment of the invention will be described, with regards to the manufacture of paintballs, although the method may be applied to the production of capsules with other applications.

[0040] FIG. 1 shows a first and a second film, 1 and 2, made from an oxo-biodegradable thermoplastic material, such as polyethylene or polypropylene, with a thickness of between 0.1 and 0.5 mm, preferably between 0.2 and 0.3 mm.

[0041] With regards to FIG. 2, a first element 10 is formed from the first film 1, and a second element 20, is formed from the second film 2. In order to do this, each film 1, 2 is heated in order to soften it, and then subject to thermoforming, using a well-known method, by applying a punch against dies, not shown here, possibly combined with aspiration or air-blowing on the dies. Through this process, the first element 10 is formed, with a first hemispheric cavity 101, and the first ring 102 surrounding the first cavity 101 as well as the first two basins 31 originating from the first ring 102 on the same side as the first cavity 101 in relation to the position of the first ring 102. The second element 20 is formed with a second hemispheric cavity 201 a second ring 202 surrounding the second cavity 201, as well as two second basins 32 originating from the second ring 202 on the opposite side of the second cavity 201 in relation to the position of the second ring 202. Several elements can be made at the same time from the same film, as it is cut before or after a thermoforming operation, to form a strip of elements 10 and 20, one after the other. When several strips have been obtained from wide films, it is possible to separate each of them and use them at different workstations, with each workstation carrying out filling and welding independently. Should one workstation become inoperative, the other workstations can continue to operate.

[0042] The first and the second elements 10 and 20 cool down after forming and hardening. They are taken to a filling workstation where a maker paint, in the form of a gel 4, is placed into cavities 101 and 201, as shown in FIG. 3. The volume of gel used is slightly higher than the volume of cavities 101 and 201.

[0043] The second element 20 is brought back and pressed against the first element 10 by a means of bringing the elements together, not represented, so that they are in a position as show in FIG. 4. During the bringing-together stage, the cavities 31 and 32 slot together by pairing the first cavities 31 with the second cavities 32, so the retention profiles 3 are formed.

[0044] The next stage is represented by FIGS. 5 and 6. The assembly 5 made up of the two elements 10 and 20 is placed in the welding means 6, between an anvil 61 and a sonotrode 62. The anvil 61 contains an anvil recess 610 which has a cylindrical shape with a circular cross-section and a striking surface 611 surrounding the anvil recess 610. The striking surface 611 is extended towards the exterior by a release surface 612, which has a truncated cone shape. The sonotrode 62 includes a sonotrode recess 620 with the same cross-section as the anvil recess 610, and a working surface 621 surrounding the sonotrode recess 620. The striking and working surfaces 611 and 621 are designed to come into contact with each other on a working area, extending around the recesses 610 and 620, the area having a width, I, of between 0.05 and 1 mm. The welding means 6, also contains a clamping means, not represented, to bring the sonotrode 62 into position and clamp it against the anvil 61. The welding means 6 also contain a means for generating ultrasound, not represented, to generate ultrasound in the sonotrode 62, which is directed towards the anvil 61. The cavities 101 and 201 of the elements 10 and 20 are housed in the anvil recesses 610 and the sonotrode recess 620, respectively, as shown in FIG. 5. The anvil and the sonotrode are slidably mounted, facing each other, on the same axis, and are activated by actuators, using, for example, pneumatics, not represented in the diagram.

[0045] During the welding stage, after the set of the two elements 10 and 20 is placed between the sonotrode 62 and the anvil 61, these components are brought together by the actuators until they clasp the rings 102 and 202. A clamping force is maintained for a sufficient period to bring the rings 101 and 202 into contact with each other, whilst expelling the gel 4 towards the exterior of rings 102 and 202. The ultrasound generation means is then activated, in order for the welding to be carried out. Whilst the pressure is maintained, power is applied at an initial level, in order to expel the residual gel 4 between the rings 102 and 202 next to the working and striking surfaces, at the edge of the cavities 101 and 201. When the material is at a sufficient temperature, the ultrasound power is increased. At the welding area, the material of the two rings 102 and 202 comes together and forms a bulge, which is expelled towards the cavities 101 and 201. The sonotrode 62 and the anvil 61 come into contact with each other in such a way that no material remains between the rings 102 and 202 and the cavities 101 and 201. The welding then ceases, the ultrasound is stopped and the cavities 101 and 102 form a capsule, in the form of a paintball, which is evacuated via one of the recesses 610 and 620. The sonotrode 62 and the anvil 61 move away and the leftover rings 102 and 202 are evacuated. The operation may be repeated in order to manufacture another capsule.

[0046] Production tests have been carried out, with variations in certain parameters. The results shown below are for tests which were carried out with one single polypropylene film with a thickness of around 0.45 mm. The width of the working surface was 0.2 mm. The cavities 101 and 201 were thermoformed to give a hemispheric shape with a diameter of around 12.7 mm. The ultrasound power was maintained at a constant level of 35 kHz throughout the entire welding and cut-out stages. An initial test stage was conducted, without fill. A second test phase was carried out, with each cavity being filled with a water-based paint in the form of a gel.

[0047] The parameters which were varied were: the air pressure in the 40 mm actuators, the duration for which the ultrasound was applied, and the power of the ultrasound (the figure of 80% given below corresponds to an amplitude of 39 μm).

TABLE-US-00001 TABLE 1 pressure at 4 bar Ultrasound Duration of Test Power welding (s) Welding Cut-out Runout 1 80% 0.1 Yes Non 2 80% 0.2 Yes Yes Good 3 80% 0.3 Open Yes

TABLE-US-00002 TABLE 2 pressure at 4 bar Ultrasound Duration of Test Power welding (s) Welding Cut-out Runout 4 90% 0.1 Yes No Poor 5 90% 0.2 Open Yes 6 90% 0.3 Open Yes

TABLE-US-00003 TABLE 3 pressure at 1.5 bar Ultrasound Duration of Test Power welding (s) Welding Cut-out Runout 7 80% 0.1 No No 8 80% 0.2 No No 9 80% 0.3 Yes No Poor

TABLE-US-00004 TABLE 4 pressure at 6 bar Ultrasound Duration of Test Power welding (s) Welding Cut-out Runout 10 80% 0.1 No No 11 80% 0.2 Yes No Poor 12 80% 0.3 Open

[0048] It was observed that from the numerous tests, very few combinations of parameters showed a positive result. The criteria which were evaluated were the following:

[0049] Welding: were the cavities joined together? If yes, were the joints open? The expectation is that the capsule is closed and completely sealed.

[0050] Cut-out: was this done?

[0051] Runout: was the bulge formed in the formed capsule? The formulation of the bugle demonstrates that welding has been successful.

[0052] It was concluded that if the duration of ultrasound is not sufficient, the cut-out is not realised (tests 1 and 2). The welding is also affected by an insufficient ultrasound duration (tests 9 and 8). Excessive power makes the duration of welding difficult to control (tests 4 and 5), making it difficult to obtain both cut-out and a well-sealed joint. The force with which the sonotrode is applied to the anvil is also crucial. If not enough force is applied, the welding joint is not well sealed (table 3). If too much force is applied, the anvil and the sonotrode rapidly come into contact with each other, causing a fault in the machine to occur, before the cut-out is realised (table 4).

[0053] With the parameters thus defined, paintballs containing water-based paint were manufactured. Test-firing was successful, in so far as the paintballs did not explode when they were fired, even when fired at high power (330 feet per second), but did explode when they hit the target. The paintball trajectory was sufficient, enabling a target to be reliably hit from a distance of 20 meters.

[0054] The invention is not restricted to the embodiment which has just been described, as an example. The cross-section of the recesses 610 and 620 may be of any diameter. The cavities 101 and 201 can also be of any shape. The cavities 101 and 201 may also be filled only partially, by a fractionated solid material, or by a liquid.