US1891452A - Can and method of sealing same - Google Patents

Description

Dec. 20, 1932. H. SCHIBSTED CAN AND METHOD OF SEALING SAME Filed Aug. 2, 1929 BY I @Mfl

ATTORNEY Patented Dec. 20, 1932- UNITED STATES,

PATENT OFFICE HELGE SCHIBSTED, OF SYRACUSE NEW YORK, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE BORDEN COMPANY, OF NEW YORK, /N. Y., A CORPORATION OF NEW JERSEY CAN AND METHOD OF SEALING SAME Application filed August 2, 1929. Serial 110,382,910.

The invention relates to an improvement in cans and methods of sealing the same, and more particularly to an improvement in sealing the joint between the ends or covers and the body portion of tin cans whether of cylindrical or other shape.

The cans for containing dry food products, such as powdered milk, are usually composed of a body portion which may be cylindrical or of other shape provided at one or both ends with a laterally extending flange or lip, and an end or cover having a laterally extending flange or lip. In closing or sealing the can the lip of the body portion and the lip of the cover are brought together and folded upon each other to form a joint hermetically sealing the contents of the can from the atmosphere. To assure an airtight joint it has been the practice heretofore to provide either the lip of the body portion or the lip of the cover with a layer of seaming material such as rubber cement which fills the space or joint between the adjacent surfaces of the lips of the can. It has been found, however, that none of the seaming preparations in use heretofore are absolutely airtight. This is particularly noticeable where the can is closed under vacuum or the contents of the can are of such a nature that they develop a vacuum in the can after the can has been closed. In the canning of powdered milk, for example, the can filled with the milk powder is subjected to a vacuum to withdraw the atmospheric air therefrom,

and particularly the oxygen, and then a non-r oxidizing gas is introduced into the can and the can is closed. In the course of time the powdered milk absorbs part of this gas and produces a partial vacuum in the can. Under such conditions even the most carefully fashioned cans in which an unstable and porous sealing substance, such as a rubber cement or other usual organic seaming substance is used to fill and seal the joint between the cover and the body portion of the can will in many instances develop a small leak and permit air'to enter the can and have a deleterious eflect upon its contents.

The object of the invention is to elfectlvely seal the joint between the mutually engaging surfaces of the lip of the cover and the lip of the body portion of the can by pro.- viding either or both lips with a film or coating of a stable, non-porous and non-volatile fore the lips are folded together to form the sealing joint. -It may also however, be applied to a filled and closed can in such manner as to be drawn into the joint between the cover and the body portion of the can by capillary attraction. tile plastic sealing substance enters the pores or minute openings in or around the usual seaming substance such as the rubber cement and establishes an impassable seal between two adjacent layers of the unstable, porous seaming substance or between a layer of the unstable, porous seaming substance and the adjacent part of the can or cover. The invention is more fully described hereinafter and is particularly pointed out in the appended claims.

In the accompanying drawing illustrating the preferred manner in which the invention is put into practice, Fig. 1 is a longitudinal section through a can cover on an enlarged scale showing the application of a layer or coating of stable, non-porous sealing substance applied to the usual seaming material on the inner surface of the flange of lip portion of the cover; Fig. 2 is a longitudinal section through one end of a can and showing the application of a layer of the stable, nonporous sealing substance to the pro ecting flange or lip thereof; Fig. 3 1s a longltudinal section through the end of the can shown in Fig. 2 to which the cover shown in Fig. 1 has been applied and the cooperatlng lips of the can and cover folded together and inwardly against the body portion of the can to establish a tight joint between them; and Fig. 4c is a longitudinal section through one end of a closed can provided in the first in- The dense non-vola porous sealing substance'has been applied according to the present invention after the closing of the can.

It is assumed that the invention is applied to a can the parts of which have beentreated as heretofore to form an air-tight. joint between the cover and the body portion of the can. Such a can is illustrated in the drawing. In Fig. 2 is shown one end of the body por- 19 tion 5- of a cylindrical can provided with a laterally extending flange or lip 6. In Fig. 1 is shown a dish-shaped end or cover consisting of the body portion 7 of the same shape as the body portion 5 of the can and 15 adapted to fit therein, as indicated in Fig. 3, when the parts are brought together to close the can, and a laterally extending flange or lip 8 having a downwardly and inwardly turned outer end 9. The diametrical distance between the inner edges 10 of the inturned ends 9 of the lip 8 is slightly greater than the diameter of the flange or lip 6 as determined by the outer edges 11 of the latter so that. the upper surface of the lip 6 may 15 contact with the under surface of the lip 8 when the cover is inserted into the open end of the body portion 5 preparatory to folding the lips together. The under surface of the lip 8 is coated with a layer of the usual seamwhich is indicated by the heavy section lines 12. This seaming material extends from the extremity 10 of the lip 8 to almost the body portioni'I of the cover. Theseaming material is applied in a layer of uniform depth in well-known manner;

When the can is closed by inserting the cover into the open end of the body portion withthe upper surface of the lip 6 lying 40 against the under surface of the lip 8, the two lips' are folded to ether in the manner shown in Fig. 3, where y the seaming material 12 is interposed as a layer between the mutually engaging portions of the lips. In

spite of the most careful adjustment of the rolls of the machines for folding the lips" together, it has been found impossible to make all thecans absolutely air-ti ht when the joint between the lips has been led with '50 only rubber cement or any other seaming materlal heretofore proposed or in use. This leakage may, or may not, be due to the fact that these cements or seaming compounds contain a certain amount of volatile ingredients, and are unstable and more. or less porous to air. Inany event, whatever the cause of the leakage, I have discovered that the leakage can be prevented if a layer or coating of a stable, non-porous and nonvolatile substance, such as mineral oil or a petroleum product, such as petrolatum with or without addition of beeswax or paraflin wax, be applied to either or to both lips, preferably before the lips are brought toa; gether for folding. The sealing substance ing material, such as rubber cement, and.

stance having an optimum yield point with a maximum mobility. I have found that a sealing composition containing oily material as its major ingredient and preferably composed of three parts of petrolatum and one part of beeswax will make a vacuum tight seal in a capillary having a diameter of .2.

mm at temperatures up to 120 F. In Fig. 1 the improved sealing substance is shown applied as a layer or coating 13 on the layer of usual seaming material 12. This layer of sealing substance is usually sufiicient to produce an absolutely tight joint between the lip ofthe cover and the lip of the body portion of the can when they are folded together. If desirable this improved sealing substance can instead be applied on the lip of the can as shown in Fig. 2 either on its upper or lower surface or both. If necessary such layer could also be applied both to the cover and to the lip of the can. However, care should in any case be taken to limit the amount of the sealing substance applied so as to avoid an excessive squeezing out of same during the seaming operation.

If the improved sealing substance is ap plied as an oil no heating may be required to cause it to adhere in an even layer of uniform depth to the surface of the seaming material or to the metal surface of the lips. But if the sealing substance is in plastic form, as

when a mixture of petrolatum and beeswax.

or parafiin wax is used, it will be desirable to heat the mixture sufiiciently'to cause it to flow smoothly when applied to the lips of the cover and the body portion of the can. The application of the sealing substance to the lips of the cover and the body portion of the can may be eflected in any preferred manner, asb v the usual lining or gumming machines. When the can lips coated 'with the improi ed sealing substance, as indicated in Figs. 1 and 2 are brought together and folded in the usual manner, some of the sealing substances will be squeezed into the slight space between the outer surface of the body portion 7 of thecover and the inner surface of the body portion 5 of the can, and between the outer surface of the body-portion of the can and the'under or inner surface 15 of the .end 9.ofthe lip 8.- as indicated at 16 and 17 respectively, in Fig. 3. y

In case abatch of cans already made up according to former practice, that is to say,

with the lip of the cover provided with a layer of seaming material of rubber cement or the like, develops an undesirably large percentage of leaky cans, these cans can be treated according to the present invention by heating the ends of the cans and applying to them a heated mixture of petrolatum and beeswax. In Fig. 4 there is represented one end of a can formed according to the former practice, the lip of the bodyportion 21 of the can being folded together with the lip 22 of the cap or cover 23 with a layer of seaming material 24 interposed between them. The mixture of petrolatum and bees wax having been melted until it flows freely and the end of the can having been heated slightly the melted mixtureiwill be applied at the point A at the junction between the bodyportion of the can and the lower end of the downturned fold 25 of the lips; the melted sealing material will flow into the slight space between the inner fold 26 of the lip 22 and the adjacent part 27 of the body portion 21 of the can as indicated by the stippled material 28, thereby eflectively seal ing the can and preventing ingress of air into the can or egress of gas from the can.

It will be understood that the illustrated cans in the drawing and especially the joints thereof between the overlapping lips are shown greatly exaggerated in order to bring out as clearly as possible the features and the principle of the invention.

Having thus described the invention what claim as new is 1. In a can for containing dry products and comprising a body portion having alip and a cover having a lip, one of said lips having on .one surface a coating of seaming material, a

layer of sealing composition of a difi'erent character than the seaming material and containing an oily material as its major ingredient applied directly on the seaming materialand forming a coating therefor,-the

sealing material being disposed toward thecontents of the can, said lips being brought together in a. joint with the seaming material and the sealing composition interposed between them. e

2. In a can for containing dry products and comprising a body portion having a lip and a cover having a lip, a seaming material on one of said li s and a layer of sealing composition of a di erent character and containing as its major ingredient stable, oily material, said composition bein contiguous to said seaming material and isposed toward the contents of the can and at least in part between it and the atmosphere,

being brought together in a joint with the and said lips material on one of said lips, and a sealing composition of difierent characteristics than the seaming material contiguous to said seaming material and disposed toward the contents of the can, said sealing material possessing the property of remaining positively and permanently airtight in the presence of dry vapor in the can and said lips being brought together in a joint with said material between them.

4. In a can for containing dry products and comprising a body portion having a lip and a cover having a lip, a coating of scaming material on one of said lips, and a sealing composition of difl'erent characteristics than the seaming material and containing stable, oily material as its major ingredient, applied directly on and forming a coating for the seaming material-and disposed toward the contents of the can, said lips being brought together in a joint with said materials beseaming material and the sealing composition,

interposed between them.

3. In a can for containing products and comprising a body portion having a lip and a cover having a 11 a coating of seaming

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