Ringless metal cans and method

Abstract

A can comprises a can body (10) and a lid (4). The can body is manufactured using only a single homogeneous piece of material and has an edge that defines a top opening into the can. The can body also has an inwardly directed bead (23), which extends around the body, is adjacent to the can body edge, and defines an inwardly facing sealing surface (24) of substantially constant transverse cross-sectional dimension along an axial extent. The lid defines an outwardly directed sealing surface which abuts the inwardly facing sealing surface presented by the inwardly directed bead in order to seal the lid to the can body. An alternative can body has an inwardly directed pinched or collapsed bead which defines an upwardly facing sealing surface (34) for engagement with a downwardly facing sealing surface of a can lid. The alternative can body additionally has an inwardly directed bead (35) between the can body edge and the pinched or collapsed bead. An outer brim (42) of the lid is configured to be retained between the two beads of the alternative can body.

Claims

1. A can comprising: a cylindrical can body being formed of only a single homogeneous piece of material that includes a can wall that extends from a base of the can body to a terminal end of the can body the terminal end defining a curled edge that extends radially outwardly from the can wall, said curled edge defining a top opening into the body, the body further comprising an inwardly directed bead pressed into the can wall and extending around the body adjacent to said edge, the bead defining a radially inwardly facing sealing surface which has a substantially constant transverse cross-sectional dimension along an axial extent and has a circular cross-section that extends about a longitudinal axis of the can body wherein said sealing surface of the bead overlaps at least partially with the curled edge in an axial direction, the axial direction being parallel to the longitudinal axis of the can body; and a lid defining an outwardly directed sealing surface abutting the inwardly facing sealing surface presented by the bead in order to seal the lid to the can body, wherein an upwardly facing surface or surfaces of the bead define, together with said edge, an annular trough located radially inside said curled edge, the annular trough having an inclined bottom surface configured to allow access to the lid by a lid removal tool.

2. A can according to claim 1, wherein the radially outermost region of the bead is collapsed in the axial direction to substantially close the bead to an area surrounding the can body.

3. A can according to claim 1, wherein the radially outermost region of the bead is collapsed in the axial direction to substantially close the bead to an area surrounding the can body and the bead has an axial cross-sectional shape that is substantially triangular.

4. A can according to claim 3, wherein said shape is substantially that of an isosceles triangle having a centre line that extends radially and is substantially in axial alignment with the closed region of the bead.

5. A can according to claim 1, wherein the inwardly directed bead has a radial depth ranging from 2 mm to 10 mm.

6. A can according to claim 1, wherein the inwardly directed bead has a radial depth ranging from 2 mm to 5 mm.

7. A can according to claim 1, wherein said sealing surface of the inwardly directed bead has an axial extent of between 2 mm to 10 mm.

8. A can according to claim 1, wherein said sealing surface of the inwardly directed bead has an axial extent of between 2 mm to 6 mm.

9. A can according to claim 1, the can body being metal.

10. A can according to claim 1, wherein the can body and the lid are configured such that, when the lid is sealed to the can body, an upper surface of the lid is located above the edge of the can body.

11. A can according to claim 1 and comprising an end secured to the can body to close a bottom opening of the can body.

12. A can according to claim 1, wherein said lid comprises a substantially flat panel having a U-shaped bead defined around its periphery, a radially outer surface of the bead providing said outwardly directed sealing surface.

13. A can according to claim 12, said lid comprising a curled peripheral edge, a lower surface of that curled edge abutting an upper surface of said inwardly directed bead.

14. A can according to claim 13, wherein the outwardly directed sealing surface is substantially flat and extends from the curled peripheral edge of the lid to a U-shaped surface of the U-shaped bead, the U-shaped surface being spaced radially inward from the outwardly directed sealing surface.

15. A can according to claim 1, wherein said curled edge extends upward in the axial direction from the upwardly facing surface or surfaces of the bead, thereby defining the top opening into the body above an uppermost portion of the bead.

16. A can comprising: a cylindrical can body being formed of only a single homogeneous piece of material and having an edge defining a top opening into the body, the body further comprising an inwardly directed bead pressed into and extending around the body adjacent to said edge, the bead defining a radially inwardly facing sealing surface which has a substantially constant transverse cross-sectional dimension along an axial extent and has a circular cross-section when viewed axially, wherein the cylindrical can body further comprises a sidewall that extends from the bead to a bottom end of the cylindrical can body, wherein the inwardly facing sealing surface is spaced radially inward from the sidewall such that a diameter of the inwardly facing sealing surface is less than a diameter of the sidewall; and a lid defining an outwardly directed sealing surface abutting the inwardly facing sealing surface presented by the bead in order to seal the lid to the can body, wherein the bead further defines by an upwardly facing surface and a downwardly facing surface that both extend from an outermost region of the bead to the inwardly facing surface, wherein the upwardly facing surface and the downwardly facing surface are substantially symmetric about an axis substantially perpendicular to the sidewall and that extends through the outermost region of the bead.

17. A can according to claim 16, wherein the inwardly facing sealing surface is spaced radially inward from the sidewall by a distance of between 2 mm and 10 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a conventional can utilising a ring, and with a lid attached;

(2) FIG. 2 is an axial cross-sectional detail of the can of FIG. 1;

(3) FIGS. 3 to 7 illustrate various stations used in the production of a novel ringless can body as well as various manufacturing states of the body;

(4) FIG. 8 illustrates a ringless can body;

(5) FIG. 9 illustrates a detail of a novel ringless can body with a lid attached;

(6) FIG. 10 illustrates a production process for manufacturing the can body of FIG. 9; and

(7) FIG. 11 is an axial cross-sectional detail of a ringless can body with lid attached.

DETAILED DESCRIPTION

(8) A conventional paint can with ring has been described above with reference to FIGS. 1 and 2. An improved ringless paint can will now be described with reference to FIGS. 3 to 10.

(9) The first stages of forming a cylindrical can body are conventional, requiring cutting of a rectangular flat sheet, rolling the sheet into a cylinder, and welding the abutting edges to form a seam. A curl is formed around the top edge of the can body in order to strengthen the edge whilst “hiding” the cut edge. An outwardly directed flange is formed around the bottom edge of the can body to allow subsequent attachment of bottom end. FIG. 3 illustrates a can body 10 formed in this manner, with a curl 11 formed around its top edge and a flange 12 directed outwardly around its bottom edge. A bottom end has not yet been attached to the can body such that the bottom remains open.

(10) FIG. 4 illustrates tools of a deep-bead forming station 13 into which the can body 10 of FIG. 3 is introduced. This station 13 is configured to form an inwardly directed bead circumferentially around the can body 10, with a predetermined depth, height and shape. A first inner tool 14 is generally cylindrical and is rotatable about the axis 28 of its cylindrical shape. A groove 15 is provided around the circumference of the inner tool 14 and has a generally rectangular cross-sectional shape. A second outer tool 16 is generally cylindrical and is mounted for rotation about its axis to rotate in the opposite direction of outer tool 16. The tool 16, and its rotational mounting, can be moved radially with respect to the axis of the inner tool 14.

(11) At the bead forming station 13, the inner tool 14 is inserted into the can body 10 through the top opening. Whilst the can body 10 remains stationary, both the outer tool 16 and the inner tool 14 mutually engage by moving radially in opposite directions. This causes a portion of the can body 10 to be pressed into the groove 15 around the inner tool 14. This is the position illustrated in FIG. 5. [Other arrangements to engage the inner 14 and outer tools 16 may also be contemplated.] The outer tool 16 is then rotated about its own axis 29. The inner tool 14 is counter-rotated about its own axis 28 (the inner tool 14 may be driven or may rotate freely). This operation causes the can body 10 to rotate about its own axis 30 such that a bead 17 is formed around the entire circumference of the can body 10.

(12) At least a rotation of just over 360 degrees is required to form the groove. However, forming the inwardly directed bead 17 normally requires between 3 to 20 revolutions of the can body 10 around its axis 30. Following this operation, the inner 14 and outer tools 16 are moved out of engagement with the can body 10. FIG. 6 illustrates the formed can body 10 following removal from the bead forming station 13.

(13) The can body 10 is then moved to a bead re-sizing station 18, the operation of which is illustrated in FIGS. 7A, 7B and 7C. This station 18 makes use of an upper bead shaping tool 19 and a lower bead shaping tool 20. These tools 19, 20 have complimentary shaped angled features 21 and 22 formed on their opposed end regions. FIGS. 7A and 7B show the upper and lower bead shaping tools 19, 20 being introduced into the can body 10. The uppermost edge of the angled feature 22 of the lower tool 20 has been introduced into the can body 10 through the bottom opening and is just engaged with the lower, peripheral region of the bead 17, whilst the upper bead shaping tool 19 is about to enter the can body 10 through the top opening. FIG. 7C shows the upper and lower bead shaping tools 19, 20 being brought together around the bead 17, pressing the top and bottom surfaces of the bead 17, at their outer peripheral regions, together, i.e. effectively pinching the bead 17 together at its outer region to form a pinched bead 23. The upper and lower bead forming tools 19, 20 are then removed from the can body 10, and the body 10 is advanced to the next station in the production line, e.g. a station that attaches the bottom end to the can body 10.

(14) FIG. 8 illustrates the completed can body 10 with pinched bead 23. FIG. 9 illustrates a cross-sectional detail of the formed can body 10, also illustrating a lid 4 in place. The pinched bead 23 is generally triangular in cross-section, with the outermost region B effectively closed by the bead shaping operation. This closure of the bead 23 is desirable to structurally reinforce the bead 23, thereby preventing a collapse under axial loading, and to prevent the subsequent ingress of product and dirt, etc., into the bead 23. The inwardly facing sealing surface 24 of the pinched bead 23 is flat in cross-section, and has a circular cross-section when viewed axially. In other words, the sealing surface 24 has a substantially constant transverse cross-sectional dimension along its axial extent. The radial depth d.sub.r of the bead 23 is preferably in the range of 2 mm to 10 mm, and more preferably in the range 2 mm to 5 mm. The closed outer area B of the bead 23 lies just beneath the curled edge 25 of the can body 10, i.e. immediately beneath that edge 25. The inwardly facing sealing surface 24 of the bead surface has an axial extent d.sub.a that is in the range 2 mm to 15 mm, preferably in the range 2 mm to 6 mm. FIG. 9 also shows the periphery of a can lid 4, which is conventional in construction, i.e. it may be a can lid that is suitable for use with a can with ring.

(15) A comparison of FIGS. 2 and 9 illustrate that the ringless design presented here has a very similar outward appearance to that of the conventional can 1 with ring 3. The ringless can 10 is adapted to receive a lever into a gap 26 between the curled edge 25 of the can body and the curled edge 27 of the lid 4 to enable the lid 4 to be prised off from the can body 10. The drip characteristics of the ringless can 10 are substantially the same as those of the can 1 with ring 3, i.e. paint or other product is captured within the gap 26 before is able to flow over the curled edge 25 of the can body.

(16) FIG. 10 presents an exemplary process for manufacturing a can as described above. Steps 100, 200 and 300 are conventional can body forming steps that take a flat metal sheet and form it into a generally cylindrical can body with a welded seam. The body is formed with a curled top edge and a flange around its bottom edge. Step 400 is an option curl re-sizing operation. Step 500 forms a deep bead around the can body, just beneath the top curled edge (see above and FIGS. 4 and 5). Step 600 collapses the bead in order to pinch the outer periphery and leave a flat sealing surface (see above and FIGS. 7A, 7B and 7C). At step 700 a bottom end is introduced and is seamed to the bottom opening of the can, making use of the previously formed flange.

(17) FIG. 11 illustrates a cross-sectional detail of an alternative ringless can design. The can body 31 comprises an inwardly directed flange 33. The flange 33 extends circumferentially around the can body 31 and has an elongate, substantially diamond-shaped or rhomboid cross-section. The flange 33 may formed by first pressing a bead into the wall and then pinching or flattening the bead. The outermost region B′ of the flange 33 is effectively closed to an area surrounding the can body 31 thereby substantially preventing the ingress of dirt or other materials into the flange. The flange 33 has an upwardly facing sealing surface 34 which extends into the can body 31 interior, in a plane substantially perpendicular to the longitudinal axis of the can body 31. The upwardly facing sealing surface 34 may comprise two surfaces slightly angled in respect of one another. The sealing surface 34 may form a peak.

(18) The cylindrical can body 31 comprises an outward curl 32 around its top edge. Between the curl 32 and the flange 33, the wall of the can body 31 is provided with a retention bead 35. The retention bead 35 is pressed into the can body 31 and forms a substantially semi-circular, inwardly directed groove around the external circumference of the can body 31. The retention bead 35 opens outwardly onto the area surrounding the can body 31 exterior.

(19) FIG. 11 also illustrates a portion of a substantially rigid can lid 38 in place on the can body 31. The lid 38 comprises a substantially flat centre panel 39 from which a downwardly dependent cylindrical side wall 40 extends. The centre panel 39 has a diameter which exceeds that of the side wall 40, such that the periphery of the centre panel 39 forms a lip 41 which overhangs the side wall 40. The side wall 40 is connected to an outer brim 42 which extends from the side wall 40 in substantially the same plane as the plane of the centre panel 39. An upwardly-opening U-shaped channel 43 runs between the side wall 40 and the brim 42. The brim 42 has an inward curl 44 at its periphery. A layer of sealing compound 37 is provided within the channel formed between the U-shaped channel 43 and the curl 44 such that a downwardly facing sealing surface of the sealing compound 37 is exposed.

(20) In use (i.e. when the lid 38 is in place on the can body 31 and the can body 31 is conventionally oriented), the sealing surface presented by the sealing compound 37 is pressed against the upwardly facing sealing surface 34 presented by the flange 33, slightly compressing the sealing compound. More particularly, the peak of the sealing surface 34 is pressed tightly into the compound 37. It will be appreciated that the compound 37 may project slightly out of the accommodating channel within the brim 42, sit flush with the surface of the channel, or even lie slightly within the channel (due to the upper surface profile of the flange 33).

(21) The lid 38 is retained on the can body 31 by engagement of the lid curl 44 below the retention bead 35. The resilience provided by the lid curl 44 allows the lid 38 to be pressed into the can body 31, past the retention bead 35, in a press or snap fit manner. This structure allows the lid 38 to be reattached to the can body 31 even after initial opening. The spacing between the retention bead 35 and the flange 33 is such that the curled edge 44 is trapped between these two features when the lid 38 is attached to the can body 31. During transportation of the can, the retention bead 35 helps prevent displacement of the lid 38 from the can body 31 caused by side impact.

(22) The ringless can is adapted to receive a lever into an annular space or gap 36 defined by the cross-sectional shape of the can body 31 and the lid 38. Application of an upward force to the underside of the lip 41 enables the lid 38 to be prised off the can body 31. As the lid 38 is prised off, the seal between the underside of the sealing compound 37 and the upper sealing surface 34 of the flange 33 is broken. The layer of sealing compound 37 is preferably retained on the underside of the brim 42 following opening.

(23) The sealing compound 37 may comprise a plastisol, for example, which may be soft when applied but may subsequently harden. The sealing compound 37 may be applied to the underside of the brim 42 of the lid 38, or to the sealing surface 34 of the can body 31. If the sealing compound 37 is initially applied to the lid 38, the sealing compound 37 may be protected, for example by a removable cover or strip, prior to placement of the lid 38 on the can body 31. This facilitates handling and storage of the lid 38.

(24) Where the can body 31 and lid 38 contain a substance such as paint, for example, a further benefit of the inwardly directed flange 33 is that it may also function as a convenient means of removing excess paint from a brush.

(25) It will be appreciated by the person of skill in the art that modifications may be made to the above described embodiments without departing from the scope of the present invention. For example, whist the pinched bead of the design described above with reference to FIG. 9 presents a flattened inwardly directed sealing surface, the surface may take another form, e.g. curved or sharp edged.

(26) The beads of the ringless cans described herein may not, in some embodiments, be pinched to complete closure, and a gap opening to the exterior of the can body may remain. Whilst the designs described above have a cylindrical can body, other can body shapes may also be contemplated, for example can bodies with a rectangular or triangular cross-section.