GB2044649A - Metal cap manufacture - Google Patents

Abstract

Metal caps 10 having a circumferential line of weakness are formed in a press tool comprising a punch 1 having a head 3 of smaller radius than its body 4 with an annular ledge 5 therebetween. A shoulder 8 formed by the parts 6,7 of a die 2 cooperates with the ledge 5 to form the weakened line. <IMAGE>

Description

SPECIFICATION Metal caps This invention relates to metal caps, and is espe cially concerned with a process for the manufacture thereof.

In particular the invention relates to the type of metal cap having on its skirt one or a series of circumferential weakening lines. One such type of cap is known as a temperproof cap, and has one or more circumferential lines of weakening on its peripheral skirt between an upper portion of the skirt, in which thread will be formed when the cap is applied to a screw-threaded bottle neck, and the lower part of the skirt which is crimped under a bead on the bottle neck. The line of weakening normally takes the form of alternate bridges and slits, and when the cap is unscrewed from the bottle the bridges break and the top may be removed. In one form all the bridges break leaving a band on the bottle neck; in another form the lower band itself splits and is removed with the rest of the cap.

Another form of cap is that wherein the line of weakening is a circumferential score line, and a tear-tab is attached to the lower part of the skirt so that such lower part may be removed by gripping the tear-tab and pulling it round the cap. This causes the lower part of the skirt to break away from the upper part along the circumferential score line.

In the manufacture of both types of cap described above, it is normal firstly to form the cap shell, in a press tool, and then in a second operation to form the circumferential weakening line.

According to the invention the circumferential line of weakening is formed at the same time as, and in the same tool as, the cap shell.

A press tool for producing a metal cap having a circumferential line of weakening comprises (i) a punch having a head, a body of larger radius than the head, and an annular ledgetherebetween, and (ii) a throat the bore of which has a portion of relatively large radius, a portion of relatively small radius, and an annular shoulder therebetween.

In operation a disc blank of cap-forming metal, e.g.

aluminium ortinplate, is shaped in the tool by relative movement of the throat and the punch, thus forming the metal blank into the shape of a cap shell, the lower edge of the skirt of which is then rolled to form a bead. The head of the punch and the throat portion of relatively small radius form between them an upper part of the cap shell of smaller radius than the part therebelow, which is formed between the body of the punch and the throat portion of relatively larger radius. The annular ledge on the punch cooperates with the annular shoulder in the throat to form a step in the skirt of the shell the metal in which is of thinner cross-section than that in the rest of the cap shell. This thinner portion defines a score-line or circumferential line of weakening.

The invention is illustrated in the accompanying drawings, which are of a diagrammatic nature, and in which: Figure 1 is a cross-section through part of a press tool in which a cap shell is being formed; Figure 2 shows part of the shell of a cap made therein; Figure 3 is a cross-section of part of a press tool for forming a slightly different cap; Figure 4 shows part of the skirt of a cap formed therein; and Figure 5 is a section on the line A-A of Figure 4.

The caps shown in the drawings are of the type having a circumferential score line separating an upper part from a lower part, and a tear-tab attached to the lower part which enables its removal.

Referring to Figure 1, a press tool includes a punch or centre block 1 and a throat 2. The punch comprises a head 3 (which may be a separate disc) and a body 4, a circumferential sharp ledge 5 being formed around the top of body 4. The throat comprises a portion 6 of relatively small radius (the top tool), a portion 7 of relatively large radius (the pressure ring), and a radiussed shoulder 8 formed at the bottom of portion 6. The cap shell 10 formed in the press tool has a peripheral skirt having an upper portion 11, a lower portion 12 and a ledge 13 of thinner material formed by compression of the material between the ledge 5 and shoulder 8.

The shell 10 is produced by relative movement between the parts of the press tool. A sheet of shellforming material is placed over the centre block 1.

The outer tool 2 then descends to (a) cut a circular blank from the sheet, (b) form the blank into a shellshape by continued downward movement, and (c) pinch the skirt of the shell, and reduce its thickness, between ledge 5 and shoulder 8. The outer tool 2 is then lifted and the shell 10 removed.

Upon removal of the shell 10 from the press tool the bottom of the skirt 12 is rolled to form a bead 14.

The lower part of the skirt 12 is then cut as shown at 15 and a tear-tab attached to the portion 16.

The tool and cap shown in Figures 3-5 are similar to those shown in Figures 1 and 2, with the exception that the circumferential weakening line 13 if formed relatively higher up the skirt, and the portion of the skirt to which the tear-tab is affixed is of a different configuration.

1. A press tool for producing a metal cap having a circumferential line of weakening, comprising (i) a punch having a head, a body of larger radius than the head, and an annular ledgetherebetween, and (ii) a throat the bore of which has a portion of relatively large radius, a portion of relatively small radius, and an annularshouldertherebetween.

2. A press tool as claimed in claim 1, substantially as described with reference to Figure 1 or Figure 3 of the drawings.

3. A metal cap produced in a press tool as claimed in claim 1 or claim 2.

The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Metal caps This invention relates to metal caps, and is espe cially concerned with a process for the manufacture thereof. In particular the invention relates to the type of metal cap having on its skirt one or a series of circumferential weakening lines. One such type of cap is known as a temperproof cap, and has one or more circumferential lines of weakening on its peripheral skirt between an upper portion of the skirt, in which thread will be formed when the cap is applied to a screw-threaded bottle neck, and the lower part of the skirt which is crimped under a bead on the bottle neck. The line of weakening normally takes the form of alternate bridges and slits, and when the cap is unscrewed from the bottle the bridges break and the top may be removed. In one form all the bridges break leaving a band on the bottle neck; in another form the lower band itself splits and is removed with the rest of the cap. Another form of cap is that wherein the line of weakening is a circumferential score line, and a tear-tab is attached to the lower part of the skirt so that such lower part may be removed by gripping the tear-tab and pulling it round the cap. This causes the lower part of the skirt to break away from the upper part along the circumferential score line. In the manufacture of both types of cap described above, it is normal firstly to form the cap shell, in a press tool, and then in a second operation to form the circumferential weakening line. According to the invention the circumferential line of weakening is formed at the same time as, and in the same tool as, the cap shell. A press tool for producing a metal cap having a circumferential line of weakening comprises (i) a punch having a head, a body of larger radius than the head, and an annular ledgetherebetween, and (ii) a throat the bore of which has a portion of relatively large radius, a portion of relatively small radius, and an annular shoulder therebetween. In operation a disc blank of cap-forming metal, e.g. aluminium ortinplate, is shaped in the tool by relative movement of the throat and the punch, thus forming the metal blank into the shape of a cap shell, the lower edge of the skirt of which is then rolled to form a bead. The head of the punch and the throat portion of relatively small radius form between them an upper part of the cap shell of smaller radius than the part therebelow, which is formed between the body of the punch and the throat portion of relatively larger radius. The annular ledge on the punch cooperates with the annular shoulder in the throat to form a step in the skirt of the shell the metal in which is of thinner cross-section than that in the rest of the cap shell. This thinner portion defines a score-line or circumferential line of weakening. The invention is illustrated in the accompanying drawings, which are of a diagrammatic nature, and in which: Figure 1 is a cross-section through part of a press tool in which a cap shell is being formed; Figure 2 shows part of the shell of a cap made therein; Figure 3 is a cross-section of part of a press tool for forming a slightly different cap; Figure 4 shows part of the skirt of a cap formed therein; and Figure 5 is a section on the line A-A of Figure 4. The caps shown in the drawings are of the type having a circumferential score line separating an upper part from a lower part, and a tear-tab attached to the lower part which enables its removal. Referring to Figure 1, a press tool includes a punch or centre block 1 and a throat 2. The punch comprises a head 3 (which may be a separate disc) and a body 4, a circumferential sharp ledge 5 being formed around the top of body 4. The throat comprises a portion 6 of relatively small radius (the top tool), a portion 7 of relatively large radius (the pressure ring), and a radiussed shoulder 8 formed at the bottom of portion 6. The cap shell 10 formed in the press tool has a peripheral skirt having an upper portion 11, a lower portion 12 and a ledge 13 of thinner material formed by compression of the material between the ledge 5 and shoulder 8. The shell 10 is produced by relative movement between the parts of the press tool. A sheet of shellforming material is placed over the centre block 1. The outer tool 2 then descends to (a) cut a circular blank from the sheet, (b) form the blank into a shellshape by continued downward movement, and (c) pinch the skirt of the shell, and reduce its thickness, between ledge 5 and shoulder 8. The outer tool 2 is then lifted and the shell 10 removed. Upon removal of the shell 10 from the press tool the bottom of the skirt 12 is rolled to form a bead 14. The lower part of the skirt 12 is then cut as shown at 15 and a tear-tab attached to the portion 16. The tool and cap shown in Figures 3-5 are similar to those shown in Figures 1 and 2, with the exception that the circumferential weakening line 13 if formed relatively higher up the skirt, and the portion of the skirt to which the tear-tab is affixed is of a different configuration. CLAIMS

1. A press tool for producing a metal cap having a circumferential line of weakening, comprising (i) a punch having a head, a body of larger radius than the head, and an annular ledgetherebetween, and (ii) a throat the bore of which has a portion of relatively large radius, a portion of relatively small radius, and an annularshouldertherebetween.

2. A press tool as claimed in claim 1, substantially as described with reference to Figure 1 or Figure 3 of the drawings.

3. A metal cap produced in a press tool as claimed in claim 1 or claim 2.

The drawings originally filed were informal and the print here reproduced is taken from a later filed formal copy.