US3620406A

US3620406A - Pull tab and pressure relief valve

Info

Publication number: US3620406A
Application number: US888793A
Authority: US
Inventors: Joseph H Evans; Fred Eugene Weir
Original assignee: Raychem Corp
Current assignee: Raychem Corp
Priority date: 1969-12-29
Filing date: 1969-12-29
Publication date: 1971-11-16
Anticipated expiration: 1988-11-16

Abstract

A pull tab for a pressurized container which can be manually removed to release the fluid under pressure and which also operates as a relief valve if the internal pressure in the container exceeds a desired level. The tab is formed in place by placing a piece of heat-recoverable plastic tubing or rod in one or more appropriately sized holes in the container and then expanded by heat to block the hole. The plastic tubing or rod then acts as a valve which relieves the container pressure upon its removal.

Description

United States Patent [72] lnventors Joseph l-l-Evans Palo Alto; Fred Eugene Weir, Atherton, both of Calif. [21 Appl. No. 888,793 [22] Filed Dec. 29, I969 [45] Patented Nov. 16, 1971 [7 3] Assignee Raychem Corporation Melllo Park, Calif.

[54] FULL TAB AND PRESSURE RELIEF VALVE 7 Clalms. 4 Drawlng Figs.

[52] US. Cl 220/44, 62/371, 220/95 [51] lnt.Cl 865d 51/16 [50] Field of Search 220/44, 53;

[56] References Cited UNITED STATES PATENTS 3,229,478 1/1966 Alonso ......,.,=:=i220/24 UX Primary Examiner-George T Hall Attorney-Lyon & Lyon ABSTRXETi lo a pressurized container which can be manually removed to release the fluid under pressure and which also operates as a relief valve if the internal pressure in the container exceeds a desired level. The'tab is formed in place by placing a piece of heat-recoverable plastic tubing or rod in one or more appropriately sized holes in the container and then expanded by heat to block the hole. The plastic tubing or rod then acts as a valve which relieves the container pressure upon its removal.

VPAIENTEUNHV men v 3.620.406

INVENTORS JOSEP H E WI/JS E E 'E/VE WE/ BY ATTGEA/EVS PULL TAB AND PRESSURE RELIEF VALVE BACKGROUND OF THE INVENTION It has recently been suggested that the contents of a can may be cooled quickly and at the desired time of consumption or other use by causing the sudden evaporation of a liquid normally a gas at atmospheric pressure. The liquid is maintained in a separate pressurized section of the can until the contents are to be cooled, at which time the pressure on the refrigerant is released by use of a suitable valve. Release of the refrigerant liquid allows it to evaporate and consequently remove the heat required for its vaporization from the contents of the can. This system requires a reliable, inexpensive, and discardable valve for venting the pressurized refrigerant. Several so-called easyopen devices have been developed which require either a deep-scoring of the container or a precisely fitted insert. When removed, the tab formed by the deep scoring of a metal container is an undesirable sharpedged piece of metal. The deep-scoring of a metal container also requires the disadvantageous weakening of the material which enhances the chance of accidental rupture. The use of a metal or plastic insert requires a relatively precise fit between the container and the insert. The insert itself is also relatively detailed and expensive. For reasons of safety, the valve must also act as a relief valve when the internal pressure exceeds a predetermined level and this requirement has been difficult to satisfy with the previously suggested devices.

SUMMARY OF THE INVENTION According to the present invention, a combined pull tab and pressure relief valve is provided which is highly reliable, is very easy to operate, and can be simply and inexpensively fabricated. These desirable features are made possible by constructing the pull tab from a piece of heat-recoverable material, e.g., tubing or rod, and using the heat-recoverable properties of the tubing to form a seal in a hole formed in one end of the container. The plastic tubing is of sufficient length to extend out far enough to allow sufficient purchase for manual removal of same. The quality of the seal is improved by providing the container end with a small cone formed by an oversized die around the hole or holes. This will relieve the concentration of shear forces on the expanded plastic where it presses against the metal of the end of the container. Use of such a cone has the additional advantages of allowing for the use of a more irregular punch with which to make the hole or holes due to the fact that the seal is made against the surface of the cone and not solely against the edge of the hole, thus reducing costs. In addition, the seal in the cone is self-tightening against internal pressure and radial shrinkage of the tube or rod can be offset by longitudinal recovery or by internal pressure.

The internal pressure of the refrigerant liquid within the can may then be relieved by manually pulling the plastic tubing or tab from the hole or holes. Also, the plastic tubing is sized so that a sufficient overpressure in the can will cause the tubing to be expelled automatically, thus preventing rupture of the can.

It is therefore an object of the present invention to provide a pressure release mechanism for a pressured container.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view, partly broken away, of a container incorporating the present invention;

FIG. 2 is a top view of the container of FIG. 1;

FIG. 3 is a detail view, partly broken away, illustrating the operation of the tab of the present invention; and

FIG. 4 is a cross-sectional detail view taken along lines 4-4 of FIG. 2.

DESCRIPTION OF THE INVENTION FIG. I illustrates a container 10, containing a consumable liquid 11, which may, for example, be beer or a soft drink. Ac-

cess to this liquid 11 is provided by a conventional removable tab 12, typically of the scribed type and located on one end l3 of the container. A generally conical wall 14 within the container defines a chamber 15 for holding under pressure a body 16 of a refrigerant liquid such as difluorodichloromethane. Preferably, the wall 14 is provided with an inner wall 17, constructed from a thennally conductive material. The wall 14 engages the wall 18 of the container 10 so that access to the consumable liquid is only through the removable tab 12.

The chamber 15 is provided with a cover 19 which engages the

walls

14 and 18 in any suitable manner to form the other end of the container 10. The cover 19 is preferably convex to increase its strength with respect to increased resistance to pressure.

As can be seen, the cover 19 is provided with a pair of

holes

20 and 21 into which extend the ends of a generally U-shaped tab or plug 22 according to the present invention. As illustrated, the tab 22 takes the form of a hollow tube. It should be understood, however, that it could be a solid rod. It should also be understood that other than two holes could be used. If one hole was used, of course, the tab 22 would have to be solid or sealed closed at least at one end. The tab 22 is preferably formed so that its main body is at an angle to its ends thereby permitting it to lie within the confines of the concave cover 19 so that it will not he accidentally released. The length or shape of the tubing making up the tab 22 is not important but it should be of sufficient size to make it easily grippable.

The tubing may be fabricated or any suitable heat recoverable plastic, care course being taken that the tubing is not degraded by the refrigerant liquid. Examples of suitable materials are, a copolymer of ethylene/vinyl acetate, low density polyethylene or a blend of low density polyethylene with a small proportion of ethylene/vinyl acetate copolymer. The latter is preferred because the copolymer content would give a slight degree of stickiness on heating. Other examples of suitable materials can be found in Cook et al. U.S. Pat. No. 3,086,242.

At least the end portions of the tab 22 are elongated while heated to above their recovery temperature and held in the elongated condition while being cooled so that they are in a heat-unstable state having a diameter less than the recovered diameter of the tubing. To install the tab, the ends of the tubing are inserted through the

holes

20 and 21 and then heated to above the recovery temperature of the material. This causes the ends to attempt to return to their original diameter, this diameter being greater than the size of the holes 20 and 2|. As a result, the tubing engages the metal of the cover 19 and forms a seal. For example, with a hole-size of 0.3 I75 cm. in diameter, a hollow tubing having a nominal diameter of 0.381 cm. and a wall-thickness of 0.0635 cm. was found to make a satisfactory seal that would withstand pressure up to about p.s.i.

A better valve is made if the holes are at the center of concave cones such as is shown in at 23 in FIG. 4. These cones are easily formed by the use of an oversized die with a correctly sized punch. The provision of a conical surface increases the surface area with which the expanded tubing can make contact and reduces the likelihood of the metal cutting into the plastic by relieving the concentration of shear forces which may develop at the edge of the hole.

FIG. 3 shows the manner in which the tab is removed from a container. There is no bending or breaking of metal or plastic. The operation is performed with one simple motion. The same effect will be produced if the internal pressure in the chamber 15 exceeds that for which the tab is designed.

While the present invention has been illustrated in connection with a coolable can, such a tab device may be used with any pressurized container where a small one-cycle valve is desired. As mentioned above, the grippable extension of the 1 tab may assume any desired configuration. The number of punched holes also may vary. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive.

What is claimed is:

l. A combined pull tab and pressure relief valve for a container having a surface having at least one hole therein, comprising a plastic member having at least a portion comprising heat-recoverable material, said portion of said plastic member being inserted into said hole and expandably heat-recovered to engage said container and seal said hole.

2. A combined pull tab and pressure relief valve for a container having a surface having at least one hole therein, comprising a plastic member having at least a portion comprising heat-recoverable material, said portion of said plastic member being inserted into said hole and expandably heat-recovered to engage said container and seal said hole; said hole in said surface being defined by a conical, outwardly concave surface.

3. A combined pull tab and pressure relief valve for a container having a surface having at least one hole therein, comprising a plastic member having at least a portion comprising heat-recoverable material, said portion of said plastic member being inserted into said hole and expandably heat-recovered to engage said container and seal said hole; said member being tubular.

4. A combined pull tab and pressure relief valve for a container having a surface having at least one hole therein, comprising a plastic member having at least a portion comprising heat-recoverable material, said portion of said plastic member being inserted into said hole and expandably heat-recovered to engage said container and seal said hole; said surface being concaved inwardly to allow retraction of said plastic member inside of the outermost plane of said surface.

5. The combined pull tab and pressure relief valve of claim 1 wherein said container is a pressurized can.

6. The device of claim 1 wherein said surface has two holes and said plastic member has at least two portions comprising heat-recoverable material, said portions being inserted into said holes.

7. A combined pull tab and pressure relief valve for a pressurized can comprising a surface of said can having two holes formed therein, a generally U-shaped plastic tubular member comprising heat-recoverable material, the ends of said plastic tubular member being inserted into said holes and expandably heat-recovered to engage said surface; said surface being formed around said holes into a cone concaved toward the outside of said can; said surface being concaved inward to allow retraction of said plastic tubular member inside of the outermost plane of said surface.

Claims

1. A combined pull tab and pressure relief valve for a container having a surface having at least one hole therein, comprising a plastic member having at least a portion comprising heatrecoverable material, said portion of said plastic member being inserted into said hole and expandably heat-recovered to engage said container and seal said hole.