Method of producing a container with a protective liner, product container

Abstract

 A method of producing a container (1) having a cup-shaped body (2) and a liner (8), the method including the steps of inserting the liner (8) inside the cup-shaped body (2); forming a vacuum inside the gap between the cup-shaped body (2) and the liner (8); and connecting the liner (8) to the inner surface of the cup-shaped body (2).

Description

[0001] The present invention relates to a method of producing a container with a protective liner.

[0002] Liquid-product containers are known comprising a metal cup-shaped body symmetrical about an axis of symmetry and having a bottom wall, and a truncated-cone-shaped or cylindrical lateral wall coaxial with the axis of symmetry; and a plastic liner coaxial with the axis of symmetry and having a truncated-cone-shaped or cylindrical lateral wall coaxial with the axis of symmetry, and a bottom wall. The top edge of the liner is turned outwards to form an annular collar coaxial with the axis of symmetry and designed to fit onto a collar of the cup-shaped body. And the liner is made of thin, single- or multilayer, flexible plastic material.

[0003] The liner is used to form a barrier, when the liquid product in the container is incompatible (and therefore capable of corroding) the metal cup-shaped body.

[0004] The liner is also used to enable more effective use of (i.e. of all) the liquid product in the container, and at the same time to simplify disposal of the empty container. In fact, once containers of the above type are emptied, the liner can be removed to 'squeeze' out any remaining product. So the metal cup-shaped body remains clean and can be either re-used or recycled cheaply and easily as scrap metal.

[0005] In various alternative embodiments, the liner is entirely thermoformed; or is made from a tube, which is cut to length and so has no longitudinal weld, and to which the bottom wall is preferably welded; or is made from a sheet of appropriate shape and size, and so has a longitudinal weld connecting the two opposite ends of the sheet to form a tube, to which the bottom wall is preferably welded.

[0006] Documents US3445031, US6216907, US2002088811, and DE902597 describe methods of producing containers with protective liners of the above type.

[0007] The liner is usually fitted manually to the cup-shaped body, and as such is both cost- and time-intensive.

[0008] It is an object of the present invention to provide a method of producing a container with a protective liner, designed to eliminate the drawbacks of the known art, and which at the same time is cheap and easy to implement.

[0009] It is a further object of the present invention to provide a container with a protective liner, designed to eliminate the drawbacks of the known art, and which at the same time is cheap and easy to produce.

[0010] According to the present invention, there are provided a production method and container as claimed in the accompanying Claims.

[0011] A number of non-limiting embodiments of the present invention will be described by way of example with reference to the attached drawings, in which :

Figure 1 shows a section of a cup-shaped body of a container in accordance with the present invention;

Figure 2 shows a section of a first embodiment of a liner of the container according to the present invention;

Figure 3 shows a section of a second embodiment of a liner of the container according to the present invention;

Figure 4 shows an enlarged detail of the Figure 2 liner-cup-shaped body contact area;

Figure 5 shows a plan view of the Figure 2 liner-cup-shaped body contact area;

Figure 6 shows a section of the cup-shaped body in the course of a first embodiment of the method of inserting the liner inside the Figure 1 cup-shaped body;

Figures 7a and 7b show alternative embodiments of a detail of the Figure 1 cup-shaped body;

Figures 8a-8e show successive steps in a second embodiment of the method of inserting the liner inside the cup-shaped body in accordance with the present invention.

[0012] Number 1 in Figures 1-8 indicates as a whole a metal container having a cup-shaped body 2 with a handle 3 for easy grip by the user. Container 1 is a so-called 'full-open' type, i.e. in which the product outlet is defined by the top cross section of cup-shaped body 2. Cup-shaped body 2 is symmetrical about a central axis X, and comprises a bottom wall 4; and a substantially truncated-cone-shaped lateral wall 5 coaxial with central axis X and tapering slightly towards bottom wall 4. The truncated-cone shape of lateral wall 5 allows containers 1 to be stacked, to reduce transportation and storage volume and, therefore, cost. The top end of lateral wall 5 is surrounded by a collar 6, the edge of which is turned outwards to form a reinforced rib 7. Containers 1 with stacked cup-shaped bodies 2 are normally transported from the container manufacturing plant to the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar).

[0013] Figure 2 shows a protective liner 8, which is fitted inside cup-shaped body 2 before container 1 is filled with the liquid product (e.g. paint or similar). Liner 8 may be fitted to cup-shaped body 2 either at the container manufacturing plant, or at the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar). Liner 8 is preferably made of single- or multilayer plastic material or polylaminate.

[0014] Liner 8 substantially comprises three different component parts 9, 10, 11, which are welded prior to assembly to cup-shaped-body 2.

[0015] More specifically, liner 8 comprises a substantially truncated-cone-shaped tubular body 9 coaxial with central axis X and tapering slightly towards the end facing bottom wall 4 in use. Tubular body 9 is substantially the same size and shape as lateral wall 5 of cup-shaped body 2. In a first embodiment, tubular body 9 is made from a tubular member cut to length, and so has no longitudinal weld. In a second embodiment, tubular body 9 is made from a sheet of appropriate shape and size, and so has a longitudinal weld joining the two opposite ends of the sheet to form a tube.

[0016] Liner 8 comprises a bottom plate 10, which is welded or otherwise joined to tubular body 9. In a preferred embodiment, bottom plate 10 is in the form of a preferably thermoformed cup-shaped body. More specifically, bottom plate 10 comprises a bottom wall 12 positioned, in use, contacting bottom wall 4 of cup-shaped body 2; and a low lateral wall 13 connected to bottom wall 12. Lateral wall 13 is substantially cylindrical and coaxial with central axis X, or is substantially the same truncated-cone shape as the bottom end portion of lateral wall 5 of cup-shaped body 2, and is preferably welded to the bottom end of tubular body 9.

[0017] The cylindrical shape of lateral wall 13 enables it to be welded to the bottom end of tubular body 9 with no wrinkling, which could result in uneven weld surfaces and so impair the airtightness, and therefore the barrier performance, of line 8.

[0018] In a further embodiment, not shown, bottom plate 10 comprises a bottom wall 12 positioned, in use, contacting bottom wall 4 of cup-shaped body 2, and which is connected, preferably welded, directly (i.e. with no lateral wall) to the bottom end of tubular body 9.

[0019] Finally, liner 8 comprises an annular top collar 11 coaxial with central axis X and comprising a low, cylindrical lateral wall 14 coaxial with central axis X and which is connected, preferably welded, to the top end of tubular body 9. A top edge 15 of collar 11 is turned outwards to form a rib 16 of substantially the same shape and size as reinforced rib 7 to which rib 16 is fitted in use. Top edge 15 is defined by an annular appendix 17 coaxial with central axis X and connected to cylindrical lateral wall 14 by a number of radial connecting bridges 19.

[0020] As shown more clearly in Figures 4 and 5, radial bridges 19 are equally spaced about central axis X, and define a number of gaps 18. Gaps 18 defined between adjacent radial bridges 19 allow air to escape, which would otherwise be trapped between the outer surface of tubular body 9 and the inner surface of lateral wall 5 of cup-shaped body 2.

[0021] Lateral wall 14 must be connected, in use, to the top outlet of cup-shaped body 2, while lateral wall 13 must adapt to the bottom end of cup-shaped body 2. In the case of a truncated-cone-shaped lateral wall 5 of cup-shaped body 2, the bottom end of lateral wall 5 is smaller in diameter than the top outlet of cup-shaped body 2. So, obviously, lateral wall 14 is larger in diameter than lateral wall 13. In the case of a cylindrical tubular body 9, the diameter of tubular body 9 is constant along its whole length, i.e. at both the bottom end for connection to bottom plate 10, and the top end for connection to top collar 11, and substantially equals the diameter of lateral wall 13 of bottom plate 10. To improve connection to top collar 11, tubular body 9 is flared at the weld stage. The flare in tubular body 9 may be located at the top end, at top collar 11 (as shown in Figure 3), or roughly halfway along the length of tubular body 9, or may be distributed along at least a portion (preferably the whole length) of tubular body 9.

[0022] Liner 8 clearly has an overlap at the top, where tubular body 9 overlaps top collar 11, thus creating a thicker portion 20 in liner 8. In a preferred embodiment not shown, lateral wall 5 of cup-shaped body 2 is shaped with a recess to accommodate the thicker portion 20 in liner 8. In other words, lateral wall 5 is divided into a cylindrical or truncated-cone-shaped bottom portion 5* coaxial with central axis X; and a cylindrical or truncated-cone-shaped top portion 5** also coaxial with central axis X and shorter in height than bottom portion 5*. Bottom portion 5* is smaller in diameter than top portion 5**. And bottom portion 5* and top portion 5** are connected to define a recess in which to accommodate thicker portion 20 of liner 8. This way, even if liner 8 is fitted to cup-shaped body 2 at the container manufacturing plant, the stacked containers 1 can be unstacked easily at the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar).

[0023] The following is a description of a method of assembling liner 8 to cup-shaped body 2 to form container 1.

[0024] As stated, liner 8 may be fitted to cup-shaped body 2 to form container 1 either at the container manufacturing plant, or at the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar). If liner 8 is fitted to cup-shaped body 2 at the container manufacturing plant, it is important to ensure that liner 8 (in particular tubular body 9) adheres perfectly to the inner surface of cup-shaped body 2, to enable the stacked containers 1 to be unstacked easily at the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar).

[0025] To ensure liner 8 adheres perfectly to the inner surface of cup-shaped body 2, a vacuum must be formed between liner 8 and the inner surface of cup-shaped body 2.

[0026] As shown in Figure 6, the assembly method comprises first applying a coating 21 of glue to the inner surface of cup-shaped body 2. In a first embodiment, glue coating 21 is applied to the inner top-end surface of lateral wall 5. In a second, preferred, embodiment, glue coating 21 is applied to the inner surface of bottom wall 4. Alternatively, glue coating 21 may be applied to both the inner surface of bottom wall 4 and the inner surface of lateral wall 5.

[0027] Glue coating 21 is applied to form a continuous annular coating, preferably coaxial with central axis X and of substantially even size. Next, liner 8 is inserted inside cup-shaped body 2, so that bottom wall 12 contacts bottom wall 4 of cup-shaped body 2. The insertion step is preferably performed using an expansion plug.

[0028] In fact, once inserted, liner 8 is expanded to improve adhesion of tubular body 9 to cup-shaped body 2.

[0029] Expansion of the plug expels any air from the gap between liner 8 and the inner surface of cup-shaped body 2. And, once the plug is expanded and the air expelled from the gap between cup-shaped body 2 and liner 8, glue coating 21 is such as to maintain the vacuum formed inside the gap.

[0030] In the Figure 7a and 7b embodiments, a substantially central through opening 22 may be formed in bottom wall 4 of cup-shaped body 2 to permit connection, when fitting liner 8 to cup-shaped body 2, to suction means (not shown) by which to form the vacuum inside the gap between liner 8 and the inner surface of cup-shaped body 2.

[0031] In a first embodiment shown in Figure 7a, through opening 22 is then closed with a plug 23 made of elastic material.

[0032] In a second embodiment shown in Figure 7b, through opening 22 is then closed with adhesive tape 24 applied to the outer surface of bottom wall 4, over through opening 22.

[0033] In this case, it is important that the adhesive of tape 24 and the glue of the continuous annular coating (i.e. coating 21) be strong enough to keep container 1 airtight and maintain the vacuum inside the gap between cup-shaped body 2 and liner 8, while at the same time enabling removal of liner 8 from cup-shaped body 2 to squeeze out all the liquid product and later dispose of the liner.

[0034] As will be clear to anyone skilled in the art, what is stated above relative to fitting liner 8 to the inner top-end surface of lateral wall 5 of cup-shaped body 2 by applying glue coating 21 also applies to other, e.g. ultrasound, thermal, laser, infrared, etc. fastening techniques. It is important to note, however, that connection of liner 8 to the inner surface (of lateral wall 5 or bottom wall 4) of cup-shaped body 2 is not a mechanical connection; and that the used liner 8 is easily removable from cup-shaped body 2 by the user to extract any residual product from liner 8.

[0035] In the event the other fastening techniques mentioned are combined with an expansion plug, liner 8 is necessarily fitted to the inner surface of cup-shaped body 2 after the plug is expanded.

[0036] On the other hand, in the event the other fastening techniques mentioned are combined with means for forming a vacuum through opening 22, liner 8 is fitted to the inner surface of cup-shaped body 2 before the vacuum is formed inside the gap between liner 8 and cup-shaped body 2.

[0037] It is important to note that, using the method described above of assembling liner 8 to cup-shaped body 2, liner 8, once container 1 is emptied, can be detached, undamaged, from cup-shaped body 2, thus leaving a plastic package containing residual liquid product, and a clean metal cup-shaped body 2 that can either be re-used or easily disposed of.

[0038] Figures 8a-8e show successive steps in the method of assembling liner 8 to cup-shaped body 2 at the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar). This is a particular method, which may be implemented as follows.

[0039] As shown in Figure 8a, for delivery from the container manufacturing plant to the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar), liner 8 is folded for easy transport and handling. More specifically, tubular body 9 is fan-folded. On arrival of the cup-shaped body 2 and separate liner 8 (with tubular body 9 fan-folded) at the filling plant where containers 1 are actually filled with the liquid product (e.g. paint or similar), rib 16 on liner 8 is fitted to reinforced rib 7 on cup-shaped body 2. And, once rib 16 on liner 8 is fitted to reinforced rib 7 on cup-shaped body 2, assembly of container 1 is completed using locking means 25.

[0040] Locking means 25 comprise a substantially annular pusher 26 coaxial with central axis X, of an outside diameter substantially approximating the outside diameter of cup-shaped body 2 and liner 8, and shaped with an annular cavity 27, which is coaxial with central axis X, faces container 1, and has a profile complementary to that of rib 16 of liner 8 and of reinforced rib 17 of cup-shaped body 2. Pusher 26 is movable up and down along central axis X, between a raised rest position and a lowered work position. In the lowered work position, pusher 26 is designed to centre liner 8 perfectly on cup-shaped body 2 and lock top collar 11 to collar 6 along the whole circumference of the collars.

[0041] Locking means 25 also comprise a thin, substantially cylindrical pusher 28 coaxial with central axis X. The outer surface of pusher 28 has an outside diameter approximating but no larger than the diameter of bottom wall 4 of cup-shaped body 2. Pusher 28 has a flat bottom surface which contacts bottom wall 12 of liner 8. And pusher 28 is movable up and down along central axis X, between a raised rest position; an intermediate position, in which it contacts bottom wall 12 of liner 8; and a lowered end position, in which bottom wall 12 of liner 8 is positioned contacting bottom wall 4 of cup-shaped body 2. As it moves down into the bottom end position, pusher 28 pushes bottom wall 12 of liner 8 onto bottom wall 4 of cup-shaped body 2 and, at the same time, unfolds fan-folded tubular body 9. The downward movement into the lowered end position is relatively slow, to enable air trapped inside the gap between liner 8 and cup-shaped body 2 to escape.

[0042] Pushers 26 and 28 are then raised into their respective raised rest positions, at which point, container 1 may be filled with the liquid product. As the column of liquid product inside container 1 rises, it pushes radially on liner 8, so that tubular body 9 adheres perfectly to the inner surface of lateral wall 5 of cup-shaped body 2, and any air still trapped inside the gap between liner 8 and cup-shaped body 2 can escape, thanks to the action of pushers 26 and 28.

[0043] Clearly, changes may be made to what is described and illustrated herein without, however, departing from the protective scope of the present invention, as defined in the accompanying Claims.

[0044] It is important to note that the method described of assembling liner 8 to cup-shaped body 2 may, in a preferred, non-limiting embodiment, be implemented with the liner 8 described above.

Claims

1. A method of producing a container (1) with a liner (8), the method comprising the steps of :

- forming a cup-shaped body (2) made of metal and having a lateral wall (5);

- forming a liner (8) made of plastic or polylaminate material and substantially complementary in shape to the cup-shaped body (2),

- inserting the liner (8) inside the cup-shaped body (2); and

- fitting the liner (8) to the cup-shaped body (2) to form the container (1) ready for being filled with a product;
the method being characterized in that the step of fitting the liner (8) to the cup-shaped body (2) to form the container (1) ready for being filled with a product comprises a sub-step of forming a vacuum inside the gap between the cup-shaped body (2) and the liner (8), and a sub-step of connecting the liner (8) to the inner surface of the cup-shaped body (2).

2. A method as claimed in Claim 1, wherein the liner (8) is connected to the inner top-end surface of the lateral wall (5) of the cup-shaped body (2).

3. A method as claimed in Claim 1 or 2, wherein the liner (8) is connected to the inner surface of a bottom wall (4) of the cup-shaped body (2).

4. A method as claimed in one of the foregoing Claims, wherein connection of the liner (8) to the inner surface of the cup-shaped body (2) is not a mechanical connection.

5. A method as claimed in one of the foregoing Claims, wherein the liner (8) is connected to the inner surface of the cup-shaped body (2) using one of the following fastening techniques : ultrasound, thermal, laser, or infrared.

6. A method as claimed in one of the foregoing Claims, wherein the liner (8) is connected to the inner surface of the cup-shaped body (2) by applying a coating (21) of glue.

7. A method as claimed in one of the foregoing Claims, wherein the sub-step of forming a vacuum inside the gap between the cup-shaped body (2) and the liner (8) comprises :

forming a through opening (22) in a bottom wall (4) of the cup-shaped body (2); and

forming the vacuum inside the gap between the liner (8) and the cup-shaped body (2) by connecting the through opening (22) to suction means.

8. A method as claimed in Claim 7, and comprising the further step of closing the through opening (22) with a plug (23) made of elastic material.

9. A method as claimed in Claim 7, and comprising the further step of applying adhesive tape (24) onto the outer surface of the bottom wall (4) of the cup-shaped body (2), over the through opening (22).

10. A method as claimed in one of the foregoing Claims, wherein the sub-step of forming a vacuum inside the gap between the cup-shaped body (2) and the liner (8) is performed using an expansion plug.

11. A method as claimed in one of the foregoing Claims, wherein the liner (8) is removable from the cup-shaped body (2), and the method comprises the further step of removing the liner (8) from the cup-shaped body (2) after use.

12. A product container (1) comprising a metal cup-shaped body (2), and a liner (8) made of plastic or polylaminate material; said container (1) being produced as claimed in one or more of Claims 1 to 11.

Drawing