Method and device for producing tear-off lids and tear-off lid

Abstract

A tear-off lid with a curled edge of the removal opening is formed such that before the edge is curled, a plastics layer provided as a band of low thickness and preferably only 0.1 mm thickness is applied to the collar of the lid ring. In this way, a good seal of the cut edge of the tear-off lid is produced economically and with the possibility for production at a high rate.

Claims

1. A method for producing tear-off lids, wherein from a lid blank a lid ring having a central removal opening which is surrounded by a sealing flange is formed by means of a punching process; the edge of the central removal opening is formed by drawing to a collar projecting away from the sealing flange; the collar is curled at the free end thereof; a tear-off film is sealed onto the sealing flange; and wherein before the curling of the free end of the collar, a band-shaped strip of plastics is applied to the inside of the collar.

2. The method as claimed in claim 1, wherein the band-shaped strip is applied at an even thickness.

3. The method as claimed in claim 1 wherein the band-shaped strip is applied at a thickness which amounts to 0.05 mm to 0.5 mm.

4. The method as claimed in claim 1, wherein the band-shaped strip is applied by spraying a liquid plastics material onto the lid ring.

5. The method as claimed in claim 4, wherein the plastics is a plastics liquefied by melting.

6. The method as claimed in claim 4 wherein the plastics is applied onto the lid ring while the ring is rotated, by spraying plastics from a spray nozzle which is held stationary in a coating position at a distance from the lid ring.

7. The method as claimed in claim 6, wherein, during the spraying, the distance between the spray nozzle and the lid ring is kept constant.

8. The method as claimed in claim 7, wherein during the spraying, the lid ring is held horizontally displaceable and in that the outside of the collar is acted upon by at least one roller in order to keep a spacing of the inside of the collar from the spray nozzle constant.

9. The method as claimed in claim 1, wherein, in order to apply the band-shaped strip of plastics, the lid ring lying horizontally is lifted in a lifting movement and toward the end of the lifting movement is acted upon by a horizontally immovably positioned roller, in that after the lifting, a spray nozzle is moved toward the inside of the collar, in that after positioning the spray nozzle, the spraying of the plastics onto the lid ring in a peripheral band takes place while the lid ring is rotatably driven, in that after application of the peripheral band, the spray nozzle is moved away from the inside of the collar and in that the lid ring is lowered toward a conveying device.

10. The method as claimed in claim 1, wherein when the collar is formed, the free end of the collar is curved inwardly.

11. The method as claimed in claim 2, wherein the band-shaped strip is applied at a thickness which amounts to 0.05 mm to 0.5 mm.

12. The method as claimed in claim 2, wherein the band-shaped strip is applied by spraying a liquid plastics material onto the lid ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further embodiments, advantages and uses of the invention are disclosed by the dependent claims and the following description making reference to the drawings, in which:

(2) FIGS. 1 to 5 are vertical sectional views through a lid blank, a lid ring and a tear-off lid to illustrate processing steps in the formation of a tear-off lid according to the prior art;

(3) FIG. 6 is a schematic side view of an apparatus according to the prior art for producing tear-off lids or for carrying out the steps according to FIGS. 1 to 5;

(4) FIG. 7 is a vertical sectional view of a lid ring during the production of a tear-off lid according to the invention;

(5) FIG. 8 is an enlarged view of a portion of the lid ring of FIG. 7;

(6) FIG. 9 is the lid ring of FIG. 7 after curling of the edge of the removal opening;

(7) FIG. 10 is an enlarged view of a portion of the lid ring of FIG. 9;

(8) FIG. 11 is a plan view of the lid ring of a tear-off lid according to the invention;

(9) FIG. 12 is a schematic representation of the processing station for applying the seal;

(10) FIG. 13 is a schematic side view of an apparatus according to the invention for producing tear-off lids with a sealed cut edge;

(11) FIGS. 14 to 17 are illustrations of the positioning of the lid ring in the processing station and the movement of the spray nozzle in a preferred embodiment; and

(12) FIGS. 18 to 21 are enlarged illustrations of the positioning of the spray nozzle for the application of the plastics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) In the introductory part, the production of tear-off lids according to the prior art as known to a person skilled in the art was described, making reference to FIGS. 1 to 6. For the avoidance of repetition, reference is made here to this description.

(14) The procedure according to the invention will now be described, wherein reference is made, where necessary, to the known apparatus and the known, production steps described above. In particular, in the apparatus and the method according to the invention for forming the lid ring from the lid blank and for the sealing of the tear-off film, the procedure as already known to a person skilled in the art is carried out.

(15) FIGS. 7 and 8 show a lid ring wherein the processing step of drawing the edge of the removal opening to form the collar 4 has already taken place. This has been performed in the processing station 24. In the preferred example according to the invention as shown, herein (or in a separate step) an inward curvature which facilitates the later curling to form the retort curl has been created at the upper end 34 of the collar 4. According to the invention, in an operation at the inside 40 of the collar 4, a plastics layer in the form of a band 32 is applied. The application of this plastics layer is preferably carried out in a separate processing station 29, as shown in FIG. 13. This processing station 29 is arranged between the drawing station 24 and the curling station 25.

(16) During curling, the band 32 made of the plastics layer forms a seal for the cut edge 31, as will now be described. The band 32 consists of a plastics material and is preferably made of a thermoplastic elastomer (TPE). TPE plastics of this type are commercially available, particularly in qualities which reliably resist the sterilization temperature during sterilization of the filled container, so that the seal formed by the band is retained during the sterilization. As shown, the band is preferably formed with uniform thickness over the whole height of the band. It is provided as a thin band which preferably has a thickness d in the range of 0.05 millimeters to 0.2 millimeters, and preferably a thickness of approximately 0.1 millimeters. The height H of the band can be, for example, 1 mm to 3 mm.

(17) The coating according to the invention takes place by means of the spraying-on of a melted, liquid plastics material, preferably the aforementioned TPE, wherein a relative movement of the nozzle and the lid ring takes place. Preferably, the lid ring is rotatingly moved in the processing station 29 (FIGS. 12 and 13) and the inside 40 of the collar 4 is moved past the exit opening of a spray nozzle from which the plastics material emerges and which nozzle is arranged to be static during the coating. Thus, the lid ring is lifted at the processing station 29, caused to rotate and the coating is activated when the lid ring has reached the right position relative to the exit opening of the nozzle. Following at least one full rotation, if a gapless peripherally extending band is formed at the inside, the lid ring with the band 32 is again moved downwardly to the conveying device, wherein the rotation is ended so that the lid ring can again be placed on the receptacles of the conveying device. Then follows the conveying to the curling station 25. The plastics material of the band 32 already starts to cool down during the coating onto the lid ring and solidifies so that during further conveying, no flowing of the plastics takes place and the band is stable in the form shown. If necessary, in the coating station or the processing station 29, a cooling means, e.g. in the form of a blower can be provided.

(18) The lid ring can be rotated at a high speed during the coating of the thin plastics band, wherein this should be understood to include a rotation of more than 200 rotations per minute. A preferred rotational speed lies in the range of 400 per minute to 600 per minute.

(19) During the coating, it is ensured that the spacing of the application opening or of the spray nozzle from the inside 40 of the collar 4 during spraying on of the liquid plastics remains substantially constant so that the thickness of the band 32 is substantially constant and the low thickness thereof is possible. This can be achieved, for example, in that the lid ring 2 is precisely centered in the processing station 29 on a receptacle and the spray nozzle with the application opening has a defined spacing relative to this receptacle. However, the transfer from the conveying means with subsequent centering requires time so that, for the very high production rates striven for, the procedure followed is preferably such that the lid ring is pressed in the processing station with the outside of the collar 4 against a roller which is precisely positioned relative to the injection nozzle position during the coating, so that the spacing of the spray nozzle from the inside 40 of the collar 4 is precisely defined by simple means. This will now be described in greater detail making reference to FIG. 9 and FIGS. 14 to 17 and 18 to 21.

(20) It is evident that the band 32 is positioned at the inside 40 of the collar 4 such that it lies closer to the plane of the sealing flange 7 than to the cut edge 31. The positioning and dimensioning of the band is approximately such that the band 32 covers the lower third of the collar 4 to the lower half of the collar 4. It is possible for the band to have a greater height H, although the material cost for the plastics used then increases, but this is not necessary for the further processing or for protection of the cut edge. In practice, the height H of the seal can be approximately 1 mm to 3 mm.

(21) The lid ring provided with the plastics band according to FIGS. 7 and 8 is provided in known manner in the processing station 25 with a retort curl 5. This station 25 operates according to the prior art with the known curling tools, so that this need not be described in detail here, being known to a person skilled in the art. A modification which is obvious to a person skilled in the art is possibly present in the tools if the collar 4 has already been bent forward at its upper edge 34 for the curling, which is preferable. It is evident, according to FIGS. 10 to 13 which show the lid ring after the turning station 26 and particularly considering FIG. 12, that during the formation of the retort curl 5, the band 32 forms a seal which prevents the entry of liquid to the interior of the retort curl. Thus the bare cut edge 31 is protected against the influence of a liquid present in the can. It is unimportant whether the curling takes place in such a way that the cut edge 31 is partially embedded in the band 32, as shown or whether it only lies against the band 32. Also the opposite, that the cut edge 31 cuts through the band 32 and lies against the metal of the inside 40 does not disturb the function of the band 32. Thus, the normal production tolerances in the formation of the retort curl 5 play no part. The plan view 12 shows the lid ring as it is transported into the sealing station 27 in which the tear-off film is sealed on over the removal opening.

(22) FIG. 13 shows the production apparatus 20 for the tear-off lid, in which a processing station 29 is provided for the coating of the band 32 on the lid ring. The processing station 29 is preferably configured according to FIG. 12 and FIGS. 14 to 21.

(23) FIG. 12 shows a support 50 which is adapted, in its diameter and form, to the lid rings 2. A lid ring 2 lies with its sealing flange 7 against the upper side of the support 50. The support 50 can be moved up and down in a known manner as with the other processing stations, so that the support can be moved downwardly in the direction of the arrow C in the drawing, by which means the support is lowered beneath the receptacles for the lid ring of the conveying device 22, such that the lid ring is again passed to the conveying device so that it can be transported to the next processing station 25. On the other hand, the next lid ring which is to be received into the processing station 29 is taken up by the receptacle 50 or is lifted off the conveying device when the receptacle 50 is moved upwardly again in the direction of the arrow B. This is fundamentally known to a person skilled in the art in a similar manner from the other processing stations and the drive for moving the support 50 up and down is shown only schematically as a box 58. This drive can be configured in known manner electrically and/or pneumatically.

(24) In the preferred processing station 29, the support 50 is displaceable resiliently in the horizontal direction of the arrow E-F relative to the vertical central axis 55. This can be carried out in various ways and in the present example is solved in that a central conical holder 52 is provided which lies fixed in the position of the central axis 55 (but is rotatable thereabout, as will be explained below) and in that elastic spring means, for example, in the form of a peripheral plastics hose 54 is provided which enables the support 50 to move in the direction of the double arrow E-F by a few tenths of a millimeter to millimeters horizontally or perpendicularly to the central axis 55, respectively. In this way, the lid ring can also be displaced by this amount in the direction of the double arrow. The spray nozzle 46 which sprays the plastics material to form the band 32 against the inside 40 of the collar 4 of the lid ring 2, however, is arranged fixed in its coating position (but displaceable into the coating position, as will be described below). The spacing of the spray nozzle 46 from the inside 40 is kept constant during the application of the plastics material in that a roller 45 which is rotatable about a vertical rotary axis is arranged adjoining the support 50. The position of the rotary axis 47 in the processing station 29 is fixed and is defined relative to the spray nozzle in the application position thereof, such that the plastics coating is carried out at a defined thickness.

(25) The displacement drive 48 by means of which the spray nozzle 46 is displaceable in the direction of the double arrow E-F is shown as a box and is, for example, configured as an electric motor or as electromagnetic or pneumatic. This displacement of the spray nozzle is shown more exactly on the basis of FIGS. 14 to 21.

(26) When the support 50 is raised, the lid ring 2 is positioned centrally to the axis 55 by the spring means 54. The spray nozzle 46 has been positioned by its drive 48 displaced toward the axis 55 or in the direction E, as shown in FIGS. 14 and 15 and FIGS. 18 and 19. In this position, on lifting in the direction of the arrow B, the spray nozzle will enter into the lid ring 2. For the preferred inwardly facing curvature of the edge 34 of the collar 4 also, there is sufficient space and the spray nozzle is not a hindrance in this moved back position for the lifting movement of a lid ring of this type. The lid ring 2 or the support 50 and holder 52 of the support is brought into rotation about the axis 55 by the drive 58, for example, at the above-mentioned rotary speed of 600 per minute. At the end of the lifting movement of the lid ring 2, the lid ring makes contact with the outside of its collar 4 against the outside of the roller 45, since the roller 45 is arranged in the processing station such that it extends into the region encompassed by the raised lid ring. The FIGS. 14 and 18 show the position during lifting shortly before the collar 4 touches the roller 45. The FIGS. 15 and 19 show the position in which the lifting movement is completed and the collar 4 lies against the roller 45. Since the position of the roller 45 in the processing station 29 is precisely defined in the horizontal direction, the position of the collar 4 where it touches the roller 45 is also precisely defined. Thanks to the spring means 54, the lid ring can be adjusted in the horizontal position such that the lid ring assumes the position of the roller 45. However, the roller 45 is rotatable but not driven itself since it takes on the rotation of the lid rings.

(27) Once the lifting is ended and once the lid ring has thus reached the position shown in FIGS. 12, 15 and 19, the spray nozzle 46 is moved by its drive 48 in the direction F and assumes its fixed application position. Since the position of the roller 45 in the processing station has been precisely defined in its distance from the spray nozzle, the inside 40 of the collar 4 is also positioned at a precise spacing relative to the spray nozzle for the spraying-on of the plastics material onto the inside 40, when the spray nozzle 46 has reached its end position in the direction F, as shown in FIGS. 16 and 20. The recess 49 in the spray nozzle 46 enables the approach of the spray nozzle 46 to the collar 4 despite the curvature of the collar at the end 34. Once the spray nozzle 46 has reached its end position, the spraying-on is started and takes place throughout a complete rotation (or, if required, a plurality of full rotations) of the lid ring. FIGS. 12, 17 and 21 show the spraying-on by the spray nozzle. In this way, the band 32 of plastics is made in a precisely selectable thickness. The height H of the band 32 depends on the selection of the spray nozzle. The spraying-on of the plastics is stopped and the spray nozzle 46 is moved back by its drive 48 in the direction of the arrow E. Furthermore, the rotation of the support 50 and the holder 52 is ended and the support 50 is moved downwardly in the direction of the arrow C, wherein the lid ring loses contact with the roller 45 again. The lid ring 2 equipped with the band 32 is again laid on the conveying means and the next conveying step takes place and conveys the lid ring equipped with the plastics band 32 to the next processing station 25.

(28) The supply of liquid melted TPE plastics to the spray nozzle 46 can take place in a fundamentally known manner in that the plastics is melted in an extruder 60 and is extruded and, for example, is fed through a heated hose line 61 in liquid form and under pressure to the processing station. This is indicated purely schematically with lines so that the actual embodiment of the entry of the line into the head containing the spray nozzle is not shown. A controllably openable and closable valve 62 which is also preferably heated, causes the start and the end of the spraying of the plastics. A control system 63 can control the outlined sequence of the lifting from the conveying means, the rotation of the support with the lid ring about the axis 55 and the displacement of the spray nozzle 46 and the start of spraying and the ending of spraying and the withdrawal of the spray nozzle, the ending of the rotation and the lowering of the support. This control system can be a control unit provided at the processing station 29 or is a joint control unit common to a plurality of, or all, the processing stations and the conveying means 22.

(29) The aforementioned FIGS. 14 to 17 show an example of the drive 48 of the spray nozzle 46 in more detail. This is movable horizontally in a linear guide in the direction E-F, which is brought about here by means of an eccentric drive. In FIGS. 18 to 21, the positioning of the spray nozzle relative to the inside of the collar 4 is shown enlarged. The channel for the plastics in the interior of the spray nozzle 46 is also shown with dashed lines. The displacement of the support 50 and thus of the lid ring 2 on contact of the lid ring with the outside of the roller 45 is indicated in FIG. 19 with the arrows G.

(30) Whilst in the present application, preferred embodiments of the invention are described, it should be made clear that the invention is not restricted thereto and can also be carried out in other ways within the scope of the following claims.