Profiled closing members with slide

[57] ABSTRACT

A method of making bags and the bags resulting therefrom wherein the bags have a top edge and first and second side edges and interlocking rib and groove element at the top edge with a slider straddling the top edge and the slider having a back and downwardly projecting sides with the sides being closer together at a closing end of the slider which extends toward the first edge of the bag and being wider apart at the opening end of the slider which extends toward the second edge of the bag and with a finger between the sides at the opening end and the bag having heat seals joining the rib and groove elements and the heat seal being wider at the first edge than the second edge and being of a width at least equal to the length of the slider from its closing end to the finger so that the slider will remain fully on the bag at the end of its travel when opening the bag.

Claims, 5 Drawing Figures

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Patented Feb. 12, 1974

3,790,992

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3,790,992

PROFILED CLOSING MEMBERS WITH SLIDE

BACKGROUND OF THE INVENTION

The invention relates to improvements in fasteners for plastic bags or the like wherein the fasteners include releasably interlocking rib and groove elements with a slider for opening or closing the rib and groove elements. More particularly, the invention relates to an improved structure which limits the travel of the slider in its movement in an opening direction so that it does not wedge or stick and does not come off the end of the fastener strips.

In plastic fasteners for bags such as the type with which the present invention is concerned, releasably interlocking rib and groove elements extend along the top of the bag from a first edge to a second edge. The rib and groove elements are on the inside facing surfaces of the sheets of the bag and a straddling slider moves along the top of the bag. The straddling slider has a back and sides which extend along the outside of the rib and groove elements, and the sides are closer together at a closing end of the slider so that the rib and groove elements are pressed into interlocking relationship as the slider moves from the first to the second edge of the bag. At the opening end of the slider, the sides are further apart and a finger extends down between the slides for separating the interlocking rib and groove elements as the slider is moved from the second to the first edge of the bag.

When the bag is opened, the only thing to stop the slider in structures heretofore available is the seam at the edge of the bag, and when the slider finger comes into contact with it, most of the slider body is already off of the bag and, therefore, can easily be twisted off. If not twisted off, it may wedge or jam or become cocked or twisted so that it is not easy to start it and move it back in the direction to close the bag.

It is accordingly an object of the present invention to provide an improved structure wherein the slider is stopped in a position so that it remains fully on the bag at one edge and cannot be twisted off and does not wedge or jam, but can easily be again pushed in its closing direction.

Another object of the invention is to provide an improved method for manufacturing a series of bags providing bag structures of the type above described wherein structures are made by a minimum of steps for rapid and efficient manufacture resulting in a reduction of cost.

Other objects and advantages will become apparent from the teaching of the principles of the invention from which equivalent structures and methods will be become apparent to those versed in the art, as disclosed in the specification, claims and drawings, in which:

DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of bags constructed and manufactured in accordance with the principles of the present invention;

FIG. 2 is a vertical sectional view taken substantially along line II—II of FIG. 1;

FIG. 3 is a vertical sectional view taken substantially along line III— III of FIG. 1;

FIG. 4 is a fragmentary end elevational view taken substantially along line IV—IV of FIG. 1; and

FIG. 5 is an elevational view illustrating steps in the method of making bags in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in FIGS. 1 through 3, the structure includes flexible plastic bags formed of plastic sheets 1 and 2. These sheets form a bag 3 which has a top edge 27, and a first side edge 28 and a second side edge 29.

Along the top edge of the bag are fastener means which include flexible rib and groove elements with the rib 6 being sized and shaped to be releasably interlockable in the groove 5 of a groove element 4.

The rib and groove elements are formed of plastic as are the sheets 1 and 2 which form the walls of the bag, and in one form these elements may all be formed in a single extrusion method by being extruded from a plastic die. While the rib and groove elements are shown as being integral with the sheets, it will be understood that the features of the invention will also apply to separate closure strips which have rib and groove elements and which are attached to sheets.

When the rib and groove elements are pressed together by the application of a lateral pressure, they interlock as shown in their relative positions of FIG. 3. When they are forcibly pulled apart as by applying a separating pressure between them, they separate as illustrated in FIG. 2.

For joining or separating the rib and groove elements which closes or opens the top of the bag 3, a straddling slider 7 is positioned at the top edge of the bag. The slider has a back 8 which slides along the top edge and sides 9 and 10 mounted on the back that extend downwardly along the outer surfaces of the rib and groove elements.

The slider has a closing end 11 and an opening end 12 with the closing end extending toward the first edge 28 and the opening end extending toward the second edge 29.

At the closing end 11 of the slider, the sides 9 and 10, as shown in FIG. 3, are sufficiently close together so that they press the rib and groove elements into interlocking position. This will occur as the slider is moved in a closing direction from the first edge 28 to the second edge 29.

At the opening end 12 of the slider, a separating finger 13 is mounted on the back 8 and extends down between the sides 9 and 10. The finger forces the rib and groove elements apart to open the top of the bag, and the sides 9 and 10 are wider spaced at the opening end to permit this separation of the rib and groove elements.

Means are provided for holding the slider 7 in its straddling position at the top edge of the bag. One of these means are shown by the upwardly facing shoulders 14 and 15 at the lower edges of the side walls. These shoulders are locked beneath the bulges formed on the outer surfaces of the sheets 1 and 2 by the rib and groove elements 4 and 5. The slider is also held onto the top of the bag by shoulders formed by an enlarged head 16 at the lower end of the separating finger 13. These shoulders lock beneath the rib and groove element and also thus lock the slider in its straddling position onto the top edge of the bag.

As will be observed from the drawings and the foregoing description, the slider will be held onto the top

3,790,992 edge of the bag in all positions. However, if the slider could be pulled off of the end of the bag, such as moving too far to the right toward the first edge 28 in FIG. 1, it could twist upwardly and wedge or jam or be lifted fully off of the top edge of the sheets. To prevent this, a stop 18 is provided which is engaged by the separating finger 13 as the slider is moved to the edge of the bag to limit the travel of the slider to traveling no further than the position shown in FIG. 1. The stop 18 is preferably in the form of a cross-seal joining the rib and groove elements which prevents them from separating. The stop may be provided by a seal created by ultrasonic welding or by the application of a heated instrument to join the rib and groove elements, but an important feature of its construction is its location. That is, it extends inwardly from the first edge 28 a distance shown at X which is at least the length of the slider from its closing end 11 to the inner surface 21 of the separating finger 13.

In the manufacture of the bags as shown in FIG. 2, the bags are formed from a front sheet which becomes the front wall 1 of the bag and a continuation of said front sheet that is folded under itself to become the rear wall 2 of the bag 32 of FIG. 1. These sheets are continuous and have at their top edge the fastener means comprised of the rib and groove elements 5 and 6. To form bags cross-seals are made which form the side edges of the bags. As shown in FIG. 5, the bags have their crossseals made so as to form a first side edge 28 of the bag 32 and a second side edge 25 of the bag 31. Individual bags are severed from each other along line 23. The cross-sealing and severing is accomplished either in a single operation by using a hot wire that seals and cuts or in two operations by the application of a broader heated sealing bar which is then cut through its center by a knife. At the top of the bag, prior to the cross-seal, the stop 18 is formed such as by ultrasonic sealing. The provision of a stop is provided for successive bags as shown by the sealed areas 26 and 36. Stop 26 extends a greater distance into the second bag 32 than into the first bag 31. That is, the portion 266 of the seal 26 is narrower than the portion 26α. Portion 266 provides the stop for the slider 35 at the end of its travel when it closes the bag 31. Portion 26α provides the stop for the slider 7 at the end of its travel when it opens the bag 32. Thus, in a single manufacturing operation correctly sized stops are made for both the first and second bags 31 and 32 by virtue of the selective positioning of the overall area 26.

The slide 7 is formed of suitable material such as being molded from relatively hard plastic. The slide may be positioned by various methods such as by having its walls forcibly separated and pushed into its straddling position over the top of the bag. While the method of FIG. 5 shows the simultaneous manufacturing of a number of bags, the end seals at the first and second edges of the bag can be placed on the bags at a separate time. The bonding or welding of the edges of the bags and the formation of the stop can be formed by various types of equipment and can utilize the method of ultrasonic welding with the aid of electrodes or heads, one type of which is known to the art as “sonotrode.”