GB1567162A

GB1567162A - One-piece thermoformaed cardboard lid

Info

Publication number: GB1567162A
Application number: GB51602/75A
Authority: GB
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1975-12-17
Filing date: 1975-12-17
Publication date: 1980-05-14
Also published as: FR2335415B1; ATA909976A; FR2335415A1; AT365124B; ES224671Y; IT1065734B; ES453979A1; DE2656293A1; CH614414A5; ES224671U; BE849525A; NL7613990A

Abstract

The hitherto conventional cardboard lids for cup-shaped containers have an attached rim and can only be produced in processes with a plurality of operations and are therefore relatively expensive. The new process makes it possible to produce a one-part cardboard lid with only two operations which are similar to deep-drawing and can be carried out at high speed and using commercially available cardboard. <IMAGE>

Description

(54) ONE-PIECE THERMOFORMED CARDBOARD LID (71) We, THE PROCTER & GAMBLE COMPANY, a body corporate organised and existing under the laws of the State of Ohio, United States of America, of 301 East Sixth Street, Cincinnati, Ohio 45202, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates broadly to a method for producing one-piece thermoformed cardboard lids having a rim which allows easy grabbing of the lid, easy closing of the drum on the packing line as well as easy opening and reclosing of the drum by the user. More particularly, it is directed to a method for two-directional thermoforming of such lids out of cardboard through one single sequence of steps.

Cardboard drum lids are generally known and used. Their manufacture is however expensive since several steps are necessary inclusive of special thermoforming of cardboard disk, glueing of a spiral wound ring to the formed disk and rolling of the ring over the top edge of the formed disk. It is also common practice to equip drums with a plastic lid. Plastic lids give less flexibility with printing techniques. They are more dangerous in use because of sharp edges.

It is also very difficult to make them antistatic. Furthermore a thermoformed plastic lid of comparable cost is less suitable for mass production, particularly in view of its diminished physical resistance such as to breakage during transportation. Cardboard being diodegradable whereas plastic is not.

it is very desirable to have a method to develop suitable cardboard lids at lesser expense. No method has been found until now, however, to form one piece cardboard lids having a rim which allows easy grabbing of the lid, easy closing of the drum on the packing line as well as easy opening and reclosing of the drum by the user.

U.S. Patent 1 575 300 to Weeks et al discloses a method and an apparatus for making bottle closures from paper stock.

The thickness of the material used and the degree to which the thermoforming process stretches and compresses the material will however not be interpreted, by anyone skilled in the art, as suggesting a solution to the present problem.

U.S. Patent 2 120 328 to Ferngren teaches a method for shaping sheet material. The method of Ferngren focuses on producing small cap-sized articles from thermoformable materials. When larger articles are to be produced, the extra material when shaping walls of trays or cups out of flat blanks is mastered through crimping, pleating or corrugating, thus using a process different from the one herein disclosed.

Irrespective of the importance Ferngren attaches to the properties of the raw material, it is not suggestive of anything which could hint towards a solution of the problem solved by the present invention, e.g. the rim which is produced could in no way give a satisfactory closing of drum type articles as the method does neither recognize nor solve the problem of vertical outer walls of rims.

U.S. Patents 221 234 to Ingersoll, 1 221 846 to Dreux and 1 904268 to Bronson all teach forming of paper-like material into trays or dishes but none discloses the twodirectional forming of the present invention.

The above five patents represent the closing prior art found, additional prior art in the field of thermoforming of cardboard and like material teaching a solution to the problem entirely different from the one solved by the present invention.

The principal objects of the present invention are recited in the ensuing paragraph in order to provide a better appreciation of the important aspects prior to describing the details of a preferred embodiment in later portions of this description.

Tie major object of the invention is the provision of a method for forming a onepiece container lid made of cardboard.

A still further object of the invention is to provide a method for forming a lid as described above, which allows easy handling for closing of containers on the packing line.

Still another object of the invention is to provide a method for forming a lid as described above which allows easy opening and reclosing of the container by the user.

Another object of the invention is to provide a method for forming such a lid through one single operation comprising a sequence of steps.

A still further object of the present invention is to provide a method for producing such lids at a high speed.

Another object of the present invention is to provide a method for forming such lids requiring a low investment in apparatus.

Another object of the invention is to provide a method for forming a lid as described in the preceding paragraphs which will allow the use of substantially regular cardboard.

The invention provides a method for making a one-piece thermoformed cardboard lid, characterized in that a) the central part of a thermoformable cardboard blank, the periphery of which is held in place, is first pushed down forming a depressed central part, the immediately adjacent material adopting an upward inclination so as to form an inside wall which is generally at right angles to ttie depressed central part, such wall ending in a generally flat or rounded top and b) the peripheral area of the cardboard beyond the top is pushed down to form an outside wall which is substantially parallel to the inside wall whereby the top forms a bridging part between the two walls.

The two walls and the bridging part form a rim dimensioned to match the rolled top edge of the container to be closed.

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the present invention, it is believed that the invention would be better understood from the following description taken in connection with the accompanying drawings representing a preferred embodiment: Figure 1 is a side view of a preferred embodiment drum lid, the left half showing a sectional elevation of said lid.

Figure 2 is a fragmentary sectional elevation of the lid of the preferred embodi ment closing a rolled edge drum.

Figure 3 is a fragmentary, side elevational view of the apparatus used to form said lid, showing the cardboard blank clamped along its periphery by a holder, ready to undergo the first thermoforming step.

Figure 4 is a fragmentary, side elevational view of the apparatus shown in Figure 3, where the step of pushing the central part of the blank down, thereby forming the inside, substantially vertical wall of the rim along a ring former as well as the bridging part, is shown.

Figure 5 is a fragmentary, side elevational view of said apparatus showing the cutting die coming down to first cut the cardboard to the desired shape and then pushing the periphery cardboard down along the ring former to form the outside vertical wall of the lid rim.

A preferred embodiment of the present invention, a drum lid, is shown in Figure 1 to have a central depressed part 2, surrounded by a rim 3 consisting of a substantially vertical inside wall 3a, a vertical outside wall 3b which is substantially parallel to said inside wall, and a bridging part 3c between said two walls.

Before starting the thermoforming operation according to the preferred embodiment, a circular blank 1 of front side white coated long fiber greyboard with a thickness of 0.88 to 0.95 mm and a weight of 720g/m2 is humidified to about 8-10% by weight, normal dry cardboard having a 6% degree of humidity. The humidifying solution also contains a coating element, be it soap or oil or silicone, to allow easier forming and release of the formed lid from the mold.

This coating element will not be needed if the cardboard blanks are already treated, for example during the printing stage, with a special varnish or a silicone.

Subsequently, the prepared circular blank 1 is introduced by a conventional means between two dies (4, 5) its periphery being clamped by a holder (6a, 6b) as shown in figure 3. Die 4 and cutting ring 8 are circled by a heating means maintaining the ztemperature of the assembly between 120 and 1 5or C, whereas die 5 and ring former 7 are also circled by a heating means main taining the temperature between 150 and 1700 C. As soon as the cardboard blank is clamped by the holder, dies 4 and 5 come down exerting a force of about 2.5 tons on the cardboard blank 1, the periphery of which is still held between the holder 6.

This stretches the cardboard material over the ring former to form a depressed central part 2 and the substantially vertical inner wall 3a of the rim and compresses it further over the top of the ring former 7. The angle formed between the depressed generally planar central part 2 and the inner wall 3a will normally be of about 92".

At this stage, some of the material will have been drawn from in between the holder sections 6a and 6b and the periphery of the blank 1 will have changed to a generally oval shape due to the fibers of the cardboard reacting differently to the stretching depending on their orientation. Cutting die 8 comes down now to cut the partially formed blank 1 to the desired final dimensions as shown in Figure 5. Thereupon, cutting die 8 continues its downward movement, thereby compressing the periphery of the cardboard blank 1 along outer wall of ring former 7, thereby forming the vertical outer wall 3b of the rim and leaving the bridging part 3c between the two walls of this rim as shown in Figure 5.

The lid being completed without need for any additional trimming operation, the molds 4 and 5 and the holder 6a and 6b open, the formed lid and the peripheral cutoff material are removed by a conventional means and a new blank is fed into the apparatus. The complete operation between the feeding of the blank and the removal of the formed lid takes 3-4 seconds in the preferred embodiment described above.

In another embodiment the above method is slightly modified in that cutting die 8 is replaced by a non-cutting die 8 which may be integral or not with die 4, and which compresses the periphery of the cardboard blank along the outer wall of ring former 7, thereby building the vertical outer wall 3b of the rim and leaving the bridging part 3c between the two walls of this rim. A subsequent sideways trimming operation will then be needed, however, if a perfect lid is desired.

It goes without saying that the methods described above can be used for lids of different formats, be it square, octagonal or any other shape, as long as all angles are rounded off.

As will be easily recognized by any person skilled in the art, the apparatus necessary for performing the above methods requires only a low investment.

A lid as described in the above preferred embodiment is especially advantageous for example for use on drums containing detergents. When using a lid according to the invention, the top edge of the drums is rolled as shown in Figure 2. On the packing line the lids are easily grabbed and fall almost automatically into place on the filled drum, thanks to the fact that there is a bridging part between the two walls of the rim. The rolled edge of the drum filling the space between the two walls of the lid rim, sufficient resistance is available for the taping operation whereby the lid is fixed on the drum. Once the drum is in use, it is very easy for the user to remove the lid repeatedly after having opened the tape and to reclose it just as conveniently.

Furthermore, speed, temperature, degree of humidity, composition of the cardboard, pressure, etc. are all interrelated, one depending on the other, and the above figures are to be considered indicative and applicable to the present preferred embodiment.

For example, if the degree of humidity of the cardboard is not slightly increased, the speed of the operation will have to be reduced accordingly. Thicker cardboard will require either a higher degree of humidity, a higher temperature, higher pressure or more time or a combination of some of these factors. The method also works if the angle between the depressed generally planar central part and the inner wall of the rim is only of 90" but this, again, would decrease the speed of the operation.

Obviously it would also work with an angle of more than 92". Lower temperatures and lower pressures obviously also decrease the speed of the operation. The above methods can also be used for any cardboard found in the trade including cardboard laminates.

While a particular preferred embodiment of the present invention has been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention and it is intended to cover in the appendent claims all such changes and modifications that are within the scope of this invention.

WHAT WE CLAIM IS: 1. A method for making a one-piece thermoformed cardboard lid, characterized in that a) the central part of a thermoformable cardboard blank, the periphery of which is held in place, is first pushed down forming a depressed central part, the immediately adjacent material adopting an upward inclination so as to form an inside wall which is generally at right angles to the depressed central part, such wall ending in a generally flat or rounded top and b) the peripheral area of the cardboard beyond the top is pushed down to form an outside wall which is substantially parallel to the inside wall whereby the top forms a bridging part between the two walls.

2. The method for making a one-piece thermoformed cardboard lid according to claim 1, characterized in that the partially thermoformed material according to step a) is cut to the desired shape before the outside wall is formed according to step b).

3. The method for making a one-piece thermoformed cardboard lid according to claim 1, characterized in that the outside wall is cut to a constant height.

4. The method for making a one-piece thermoformed cardboard lid according to

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. planar central part 2 and the inner wall 3a will normally be of about 92". At this stage, some of the material will have been drawn from in between the holder sections 6a and 6b and the periphery of the blank 1 will have changed to a generally oval shape due to the fibers of the cardboard reacting differently to the stretching depending on their orientation. Cutting die 8 comes down now to cut the partially formed blank 1 to the desired final dimensions as shown in Figure 5. Thereupon, cutting die 8 continues its downward movement, thereby compressing the periphery of the cardboard blank 1 along outer wall of ring former 7, thereby forming the vertical outer wall 3b of the rim and leaving the bridging part 3c between the two walls of this rim as shown in Figure 5. The lid being completed without need for any additional trimming operation, the molds 4 and 5 and the holder 6a and 6b open, the formed lid and the peripheral cutoff material are removed by a conventional means and a new blank is fed into the apparatus. The complete operation between the feeding of the blank and the removal of the formed lid takes 3-4 seconds in the preferred embodiment described above. In another embodiment the above method is slightly modified in that cutting die 8 is replaced by a non-cutting die 8 which may be integral or not with die 4, and which compresses the periphery of the cardboard blank along the outer wall of ring former 7, thereby building the vertical outer wall 3b of the rim and leaving the bridging part 3c between the two walls of this rim. A subsequent sideways trimming operation will then be needed, however, if a perfect lid is desired. It goes without saying that the methods described above can be used for lids of different formats, be it square, octagonal or any other shape, as long as all angles are rounded off. As will be easily recognized by any person skilled in the art, the apparatus necessary for performing the above methods requires only a low investment. A lid as described in the above preferred embodiment is especially advantageous for example for use on drums containing detergents. When using a lid according to the invention, the top edge of the drums is rolled as shown in Figure 2. On the packing line the lids are easily grabbed and fall almost automatically into place on the filled drum, thanks to the fact that there is a bridging part between the two walls of the rim. The rolled edge of the drum filling the space between the two walls of the lid rim, sufficient resistance is available for the taping operation whereby the lid is fixed on the drum. Once the drum is in use, it is very easy for the user to remove the lid repeatedly after having opened the tape and to reclose it just as conveniently. Furthermore, speed, temperature, degree of humidity, composition of the cardboard, pressure, etc. are all interrelated, one depending on the other, and the above figures are to be considered indicative and applicable to the present preferred embodiment. For example, if the degree of humidity of the cardboard is not slightly increased, the speed of the operation will have to be reduced accordingly. Thicker cardboard will require either a higher degree of humidity, a higher temperature, higher pressure or more time or a combination of some of these factors. The method also works if the angle between the depressed generally planar central part and the inner wall of the rim is only of 90" but this, again, would decrease the speed of the operation. Obviously it would also work with an angle of more than 92". Lower temperatures and lower pressures obviously also decrease the speed of the operation. The above methods can also be used for any cardboard found in the trade including cardboard laminates. While a particular preferred embodiment of the present invention has been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention and it is intended to cover in the appendent claims all such changes and modifications that are within the scope of this invention. WHAT WE CLAIM IS:

1. A method for making a one-piece thermoformed cardboard lid, characterized in that a) the central part of a thermoformable cardboard blank, the periphery of which is held in place, is first pushed down forming a depressed central part, the immediately adjacent material adopting an upward inclination so as to form an inside wall which is generally at right angles to the depressed central part, such wall ending in a generally flat or rounded top and b) the peripheral area of the cardboard beyond the top is pushed down to form an outside wall which is substantially parallel to the inside wall whereby the top forms a bridging part between the two walls.

4. The method for making a one-piece thermoformed cardboard lid according to

claims 1 or 2, characterized in that it consists of one uninterrupted sequence of steps.

5. The method for making a one-piece thermoformed cardboard lid according to claims 1, 2, 3 or 4, characterized in that the degree of humidity of the thermoformable cardboard blank is 8 % to 10 % by weight.

6. The method for making a one-piece thermoformed cardboard lid according to claims 1, 2, 3 or 4 characterized in that the thermoformable blank is a cardboard laminate.

7. A method for making a one-piece thermoformed cardboard lid when carried out substantially as hereinbefore described with reference to the accompanying drawings.

8. A one-piece thermoformed cardboard lid when produced by the process of any of the foregoing claims.