Flexible continuous slide closures

The invention relates to flexible continuous slide closures of the type having pairs of strips having continuous interlocking complimentary ribs and groove elements, and more particularly to a flexible reopenable slide closure structure incorporating a closure slider for, and a method of closing, such strips which have three or more cooperating pairs of rib and groove elements.

In flexible fastener strips of the type that are formed of plastics materials manufactured by continuously being extruded from a die, the rib and groove elements are matingly shaped so as to interlock when pressed together in a direction normal to the strips. In applying a closing pressure, tie strips are pressed together either between a thumb and forefinger or by a slider which is moved along the strips. The ribs and grooves are forced into interlocking positions as the normal pressure is applied, with the rib element forcing the complimentary groove element open as it is pushed into it and deflecting its sides sideways until the groove formed between adjacent rib elements opens far enough to admit the opposing rib element which then interlocks in the groove element.

On heavy duty strips of the type which have three or more tracks, closure cannot be accomplished without considerable effort because the lateral deflection is impeded. In other words, as ribs are pressed into the grooves on heavy duty strips each haying three ribs and three grooves, the ribs forming the sides of one groove, cannot push apart, but instead will fight each other. As the ribs on each side of the

-3outside grooves spread apart, the ribs on each side of the middle groove will move towards each other so that it reduces the size of the middle groove.

In order successfully to close the fastener, the ribs must spread so that each of the grooves defined therebetween is made wider to admit the complimentary ribs of the opposing strip. While this is possible on a two track fastener, it is not possible on a three or more track fastener. Thus, it has been found to be considerably impractical to attempt to close a heavy duty fastener with three or more tracks, due to the fact that the strips fight each other so that when the sides of the groove tend to spread to open one groove, another of the grooves closes instead of opening. This problem is further aggravated when the fastener being closed is constrained by the sides of a slider that is closing it. Added to the problem described above is the friction of the extra substantial surface of the strip that is being forced laterally outwardly during the interlocking phase. This can be overcome in part by putting a coating of silicone on the strip. However, while this permits the slider to move more easily, it does not accommodate the problem of affording more space for the ribs and grooves to bypass each other and to snap into position.

The present invention is based upon a method wherein the different ribs and grooves of each of the strip tracks are closed progressively, one after another, so that each one has enough room to interlock before the next one to it is required to respond in, the same way. This can be accomplished by a structure that provides for an angled indentation

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-4or for welding an angle bar either on the top or bottom of the inside slider surface between the end of the slider and the separating bridge. The angled bar successively deforms and interlocks the ribs and grooves one after the other from one side to the other side of each of the strips.

In accordance with one aspect of the present invention there is provided a flexible reopenable slide closure structure comprising first and second flexible continuous fastener strips each having parallel portions providing at least three rib and groove elements which extend along the associated strip and are interlockingly releasable with the corresponding elements on the other strip and a closure slider positioned on said strips and having means for guidingthe slider along the strips and having first and second surfaces in opposing relationship for pressing the strips together when moved in a closing direction along the strips, one of said surfaces having a ridge for pressing the strips

2o together, said ridge extending laterally across the strips and having a first portion and a second portion with the second portion being located in successive relationship to the first in said closing direction so that at least one cooperating pair of said corresponding rib and groove elements is pressed into interlocking relationship at a different time from the other rib and groove elements so that aid rib and groove eLements do not laterally fight each other in moving to interlocking relationship.

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In accordance with another aspect of the present invention there is provided a method of closing first and second flexible continuous fastener strips each having parallel portions providing at least three continuous rib and groove elements which extend along the associated strips and are interlockingly releasable with the corresponding elements on the other strip comprising the steps of pressing the strips together to force the respective corresponding rib and groove elements into interlocking relationship by applying a closing pressure which is applied to at least one of the co-operating pairs of rib and groove elements later in time than to other such oairs of ribaid groove elements so that the rib and groove elements do not fight each other in moving to interlocking relationship.

The invention and preferred aspects thereof

-61 will now be described, by way of example only with reference to the accompanying drawings, in which:

Figure 1 is an end elevational view of a slider straddling flexible plastics fastener strips constructed and operating in accordance with the present invention, with the strips in cross section;

Figure 2 is a longitudinal sectional view taken substantially on line II-II of Figure 1;

Figure 3 is a top plan view partly in section and taken generally on a line whose extremities are indicated by III-III of Figure 2;

Figure 4 is a cross sectional view taken substantially on line IV-IV of Figure 2;

Figure 5 is a cross sectional view taken substantially on line V-V of Figure 2;

Figure 6 is a cross sectional view taken substantially on line VI-VI of Figure 2;

Figure 7 is a side elevational view of the slider taken from the side opposite to that of the view of Fiaure 2, and

Figure 8 is a perspective view of the slider. Referring now to the figures of the drawings.

Figure 1 illustrates a pair of flexible plastic fastener strips which are of identical construction.

Each of the strips has a series of interlocking ribs or teeth with grooves therebetween and facing the other strip. The grooves and ribs are defined bv continuous portions of the strips and the strips are interlocked by pressing them toward each other. In fastener strips which are provided with only one or two interlocking ribs and grooves on each of the strips, as the strips are pressed together, the ribs at each side of a groove will spread apart to provide access to the groove for the opposing rib. Where there are three or more ribs and grooves involved, this cannot

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-71 occur as will become more clear.

The upper strip 10 has a thicker marginal portion 10a which contains the ribs and grooves, and a web portion 10b which may be attached to a sheet or film by heat welding or may be integral with a sheet or film. The lower strip 11 also has a thicker marginal portion 11a and a web portion lib along the side. Each of the strips may have a slight recession or notch 12, 13 between the marginal portion and the web to accommodate easier flexing between the marginal portion and the web.

The strip 10 has shaped ribs 18, 19 and 20 and grooves 15, 16 and 17. The ribs define the grooves 16, 17 and the groove 15, that is, the groove next to the web lob is formed between the rib 18 and a shoulder loc in the strip 10.

The strip 31 has ribs 24, 25 and 26, and grooves 21, 22, and 23. The groove 23 is formed between the rib 26 and a shoulder 11c in the strip 11.

In strips which have only two grooves, when one strip is to interlock with another strip, the ribs and shoulders on the outside tend to spread apart, and the rib between the grooves tends to remain stationary. By virtue of the outwardly located ribs spreading apart, the grooves become wider to admit the opposing ribs. However, when the strips have three grooves, both centre ribs tend to remain stationary or even move towards each other and the middle groove does not get any larger and does not admit its opposing rib. More specifically, when the two strips shown in Figure 1 are pressed together in a usual fashion by merely applying a closing pressure normal to the surfaces of the strips, the outer rib 20 and the shoulder 10c tend to spread apart and the outer grooves 15 and 17 tend to widen, but the inside

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-81 ribs 18 and 19 have nowhere to shift, and the centre groove 16 does not open up to admit its tooth. If either of the ribs 18 or 19 tend to spread apart to widen the centre groove 16, they are then moving in a direction to close the grooves 15 and 17 outwardly of them. With this result, the ribs tend to fight each other in a three groove strip and the strips cannot readily interlock together by normal pressing as is possible with two groove strips. This results in the strips tending to flatten out without the grotves opening, so that the strips resist being pressed together. This difficulty is aggravated when heavier material is used such as is normally necessary with a stronger fastener of the type that requires three or more grooves. The heavier material does not flex as easily, and three groove fasteners have been found to function unsatisfactorily because of this difficulty.

A slider 27 is provided which closes the

2o three groove fastener in a progressive manner so that the ribs are not shifted against each other, and the strips close and interlock with a similar coaction to that occuring in a one or two groove strip. The slider 27 is slidably mounted on the strips so that they close when the slider is moved in a closing direction indicated by the arrowed line c in Figures 2 and 3, and the strips will open and separate when the slider is slid in an opposite opening direction.

The slider 27 is formed of metal, but may be made of molded plastic or other similar material and is generally S shaped when viewed from the closing end.

The slider is arranged to have confronting surfaces 33 and 34 which press the strips towards each other. The surface 3 for one of the strips is constructed so as to have a raised ridge 35 extending

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-9at an angle to the direction of movement of the strips so that the strips are progressively interlocked with one rib first being pressed into its opposing groove and then the next succeeding rib, and then the next, thereby permitting the ribs on the one strip to spread open their respective grooves on the other strip one at a time.

At the sides of the slider and defining a channel for the strip 10 are inner shoulders 29 and 30 which hold the slider in alignment with the strip and permit it to slide therealong. For the other strip 11, the slider has similar inwardly facing shoulders 31 and 32, which slide along the sides of the strip to hold the slider in alignment.

At the opening end is a transverse separator finger 28 joining the shoulders 30 and 31, Figures 2 and 7 and 8, which pulls the strips apart to separate them when the slider is moved in an opening direction.

For manually drawing the slider along, it has a projection 37 and an opening therethrough for a tab 36 for gripping and pulling the slider.

The closing ridge 35 which extends at an angle to the direction of the strips is shown in detail in Figures 2 to 6. As the slider moves in a closing direction, the ridge 35 presses the top strip against the lower strip which is firmly supported on the surface 34 of the slider. The strips begin to interlock, with the rib 24 on the lower strip first entering the groove 15 of the upper strip, Figure 4. Immediately following the upper strip rib 18 enters the groove 21 of the lower strip. Next, the lower strip rib 25 enters the upper strip groove 16 and then the upper strip rib 19 enters the lower strip groove 22, Figure 5. Next, the lower strip rib 26 enters the upper strip groove 17 and finally, the upper strip rib 20 enters the lower groove

-ιοί 23, until the fastener is closed, as shown in Figure

6. During the progressive action, the ribs beside each of the grooves can spread apart to open the groove, and essentially the ribs are progressively moving to the right, Figures 'i and 5, as the strips are pressed together, and then snapping into place. The ridge 35 essentially performs a sort of a twisting action on the fastener permitting progressive closing. While the ridge 35 is preferably continuous, it may be considered as having a series of portions with a first -leading portion first pressing the ribs and grooves at one side of the strip together and then successive portions pressing laterally successive portions of the strip together. A continuous angular shape of the ridge is preferred because of the smooth progressive action, but other variations in shapes and projections may be employed in accordance with the invention.

When the slider is moved in the opposite direction and the strips are pulled apart, the ribs can elongate or stretch out and thereby become narrower so that a problem is not presented by an opening process. However, when the strips are normally pressed together by methods heretofore used where a pressure is applied uniformly across the strip, the ribs tend to flatten out and try to find a position where the groove will widen and admit the opposing ribs and this flattening further complicates and aggravates the problem so that the grooves do not open, and as a result, the strips will not interlock.

By the present structure and arrangement, the strips will interlock as smoothly as if strips with a single or two grooves were used, and the arrangement will readily accommodate itself to very stiff thick strips, and also to strips having more than three grooves and

5 ribs.