Oscillating grip strip for recloseable plastic bags and method and apparatus for making the same

Abstract: A plastic bag with a recloseable zipper-type (12,14) closure is formed with grip strips (36,38) on its lips (32,34) to ease the opening of the bags. The grip strips are extruded from a grip strip extruder (40) which is moved relative to a movement of the zipper type profile to produce a regularly repeating pattern. The strips facilitate opening the bag even with wet or oily fingers. A method and apparatus for forming the same is also disclosed.

Description: BACKGROUND OF THE INVENTION a. Field of Invention The present invention relates to recloseable plastic bags, and more particularly to plastic bags having grip strips on their lips to facilitate the handling of the bags. b. Description of the Prior Art Plastic bags, and especially plastic bags with a zipper type recloseable closure have gained wide acceptance as a means of shipping and storing foodstuff as well as various other articles. Typically, these types of bags, at their opening end, are provided with two zipper strips. These strips may be formed integrally with the bag body or formed separately and attached to the film which provided the bag body. Each of these strips contains an interlocking profile and a lip disposed outwards of said profile. A problem that sometimes arises with these bags is that since they are typically made of a polyethylene they tend to feel slippery to the touch and as a result the lips are difficult to grip. The problem is somewhat exacerbated, when, as is often the case, the plastic bags are used for foodstuff and other materials used around a house and especially in the kitchen and the user's fingers are wet or oily. In such situations the bag lips become even more slippery and more difficult to handle. U.S. Patents No. 5,009,828 and N° 5,092684 disclose a plastic bag having a plurality of parallel ridges on the lips to assist gripping the bag lips. However, these ridges have drawbacks since they extend parallel to the zipper profile and therefore tend to act as rails for a user's fingers rather than to provide a gripping surface. Further, such grip strips ridges are difficult to make, requiring a rather complicated die and head for the extrusion process. DE-A-2263624 relates to a portable and not reclosable bag provided with parallel or oscillating strengthening ribs about its mouth. OBJECTIVES AND SUMMARY OF THE INVENTION In view of the above, it is a principal object of the present invention is to provide a recloseable plastic bag with an effective grip strip on its lips. A further object is to provide a recloseable bag with grip strips which are convenient to form, utilizing conventional extrusion equipment and using a minimal amount of material. A still further object is to provide on improved apparatus and method for forming such grip strips. The recloseable bag, zipper, apparatus and method according to the invention are mainly defined in the appended claims 1, 13, 22 and 31. Other objects and advantages of the invention will become apparent from the following description of the invention. Briefly, a plastic bag constructed in accordance with the present invention includes two sidewalls with edges and a recloseable zipper consisting of two mating profile strips. The zipper strips are provided with separating lips located between the profiles and the bag sidewall edges. The zipper and lips may be integrally formed with the bag sidewalls or comprise separate strips attached to a film used to form the bag sidewalls. Grip strips are extruded onto the lips by extruders which are moved relative to a movement of the sidewalls. By reciprocating the grip strip extruders transverse to the direction of movement of sidewalls an oscillating or generally sinusoidal pattern is produced to facilitate their grasping and the opening of the bag wherein the grip strips are shifted longitudinally with respect to one another. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a fragmentary sectional view taken in the direction of extrusion of a plastic profile film material from which recloseable bags may be formed and to which a grip strip is being applied in accordance with the present invention; Figure 2 depicts a side sectional view of a bag formed from the film material of Figure 1; Figure 3 shows a plan view of the bag of Figure 2; and Figure 4 shows an alternate embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION As shown in the figures, a typical recloseable plastic bag film 10 is blown or cast to provide the film material which ultimately is formed into recloseable plastic bags. Thus, as shown in figure 1 the film 10 is initially blown as a tube with integral male and female profiles 12, 14 formed on the interior surface thereof. As well known in the art, the tube is slit along line S-S between the profiles and collapsed as shown in Fig. 2 with the profiles joined to form two parallel sidewalls 16, 18 carrying profiles 12 and 14 respectively and with the slit line defining top edges 20, 22 for the sidewalls. The profiles 12, 14 then provide the zipper for a recloseable bag 24 formed by slicing and sealing the side edges of an appropriate length of tubing. In a conventional manner, two parallel ridges 26, 28 are provided on the outer surface 30 of film 10 on opposite sides of the male profile 12. These ridges add support to the profile 12 and also provide a finger guide to aid in closing the bag ultimately formed from the tubing. Similar ridges may be provided on opposite sides of the female profile 14. The portions of the film 10 extending between the profiles 12, 14 to the edges 20, 22 defined by the slit line S-S form two lips 32, 34 for the recloseable bag formed from the film. Thus,the bag is opened by gripping each lip 32, 34 and separating them thereby disengaging the profile members 12, 14. As explained above, the plastic material from which the film 10 is extruded is usually polyethylene which has a slippery feel tending to make it difficult to grip and separate the lips 32, 34, especially with wet or oily fingers. In order to alleviate this problem, in accordance with the present invention undulating or oscillating grip strips 36, 38 are added on the outer surfaces of the film in the region to be formed into lips 32, 34 respectively. Each of these grip strips 36, 38 has a sinusoidal shape so that it oscillates back and forth between one or both of the profiles 12 and 14 and the respective edges 20, 22 of the bag. Grip strips 36, 38 provide sufficient resistance to slippage to enable a person to open the bag 10 easily even with wet or oily fingers. At least one lip is provided with a second sinusoidal grip strip which is longitudinally shifted with respect to the first one. As shown in Figure 2, this second strip 36' may be formed so it is out of phase from strip 36 by 180°. Alternatively, a second grip strip 36'' may be provided which is out of phase or longitudinally offset from strip 36 by any arbitrary angle, as shown in Figure 4. The grip strips 36, 38 may readily be extruded onto the bag forming film by separate reciprocating extruder head output nozzles 40 in line with the extrusion equipment. Alternatively, in flat sheet extrusion it may be desireable to have the sheet pass beneath separate reciprocating extruder head nozzles 40 to obtain the desired grip strips. In such an instance, the grip strips will be on the same side as the profiles, or the inner surface of the film, and will provide the additional advantage of keeping the lips separated from each other so that they may be more easily grasped. As shown in Figure 1, for this purpose a pair extrusion heads are disposed with their output nozzles 40 spaced apart from the film 10 in the region of lips 32 and 34. The output nozzles 40 are coupled to a reciprocating mechanism 42 which moves the nozzles 40 transverse to the direction of extrusion of the tube 10 (which is moving out of the paper in Figure 1) thereby obtaining the desired sinusoidal pattern on the film. As nozzles 40 reciprocate in this manner, they extrude thin streams of plastic material onto the film as shown. Strip 36' (or strip 36'') is generated in a similar manner using additional reciprocating extruder head output nozzles as required. Obviously numerous modifications may be made to the present invention without departing from its scope as defined in the appended claims. For example, more complex oscillating patterns may be generated by adding additional extrusion head nozzles and changing the nature of movement of one or more of the extruder head nozzles. Such movements could be towards and away from the zipper film (up and down relative to the film), back and forth in the direction of the zipper film or any combination of these or other movements. Also, the speed of the nozzle movement may be either constant or varied. Also, while the present invention has been described in the context of an integrally formed profile film, the zipper strips and bag body film may be separately formed and then attached to provide the zipper film. That is, the zipper may be in the form of a separately extruded strip to be attached to a separately formed film to provide the stock from which the bags are to be formed. The grip strips may then be applied before or after the zipper strips are attached to the film stock. Additionally, the grip strips may be on the side of the film opposite the profiles as depicted in the preferred embodiment or one or more of the grip strips may be on the same side of the film as the profiles, as indicated, in the case of cast film extrusion. Finally, while the above description contemplates moving the nozzle head to obtain the desired grip strip pattern, in some cases it may be easier to move the film or zipper with respect to the nozzle to obtain the desired pattern. That is, as the film or zipper is moved longitudinally past the nozzle, it may also be reciprocated transversely to obtain the oscillating pattern.

Claims: A recloseable plastic bag comprising : first and second sidewalls (16, 18) each extending to a top edge (20, 22); first and second mating profile means (12, 14) each disposed on an inner surface of one of said sidewalls (16, 18) to form a recloseable closure ; a lip (32, 34) defined between each of said profiles (12, 14) and its associated sidewall top edge (20, 22); and at least two grip strips (36) disposed onto one of said lips (32, 34) and which extend in the same direction as said profile means (12, 14) characterized in that said two grip strips (36, 36', 36'') oscillate toward and away from said top edge (20, 22), said two grip strips being shifted longitudinally with respect to one another. The bag of claim 1 wherein said grip strips (36) are extruded onto said one lip (32) by a movement of two outlet nozzles (40) of an extruder for said grip strips (36) relative to a movement of said profile means (12, 14). The bag of one of claims 1 or 2 further comprising a second grip strip (38) provided on the other lip (34). The bag of one of claims 1 to 3 wherein one of said grip strips (36', 36'') provided on said one lip (32), intercepts the other grip strip (36). The bag of one of claims 1 to 4 wherein at least one of said grip strip (36) is generally sinusoidal. The bag of one of claims 1 to 5 wherein each of said grip strips (36, 36') is sinusoidal and offset one another. The bag of one of said claims 1 to 6 wherein each of said grip strips (36, 36') is sinusoidal and offset from one another by 180°. The bag of one of said claims 1 to 7 wherein said other lip (34) comprises at least two additional grip strips (36, 36', 36'') extending in the same direction as said profile means (12, 14), said two additional grip strips oscillating toward and away from said top edge (20, 22) and being shifted longitudinally with respect to one another. The bag of claim 8 wherein said two additional grip strips (36, 36', 36'') intercept each other. The bag of one of claims 8 or 9 wherein said two additional grip strips (36, 36', 36'') are sinusoidal and offset from one another. The bag of one of claims 8 to 10 wherein said two additional grip strips (36, 36', 36'') are sinusoidal and offset from one another by 180°. The bag of one of claims 1 to 11 wherein said mating profile means (12, 14) are integral with said sidewalls (16, 18). A zipper comprising : a first strip terminating in a first edge (20) ; a second strip substantially coextensive with said first strip, terminating in a second edge (22) ; a first profile (12) disposed on said first strip and defining a first lip (32) with said first edge (20) ; a second profile (14) disposed on said second strip, defining a second lip (34) with said second edge (22) and cooperating with said first profile (12) to form a recloseable closure ; and at least two grip strips (36) disposed on said first lip (32) ; characterised in that said two grip strips (36, 36', 36'') oscillate toward and away from said first edge (20) and are shifted longitudinally with respect to one another. A zipper according to claim 13 wherein said two grip strips (36, 36', 36'') intercept each other. A zipper according to one of claims 13 or 14 wherein said two grip strips (36, 36', 36'') are sinusoidal and offset from one another. A zipper according to one of claims 13 to 15 wherein said two grip strips (36, 36', 36'') are sinusoidal and offset from one another by 180°. A zipper according to one of claims 13 to 16 wherein at least a second oscillating grip strip (38) is disposed on said second lip (34). A zipper according to one of claims 13 to 17 wherein said second lip (34) comprises at least two grip strips (36, 36', 36'') extending in the same direction as said profiles (12, 14), which oscillate toward and away from said second edge (22) and are shifted longitudinally with respect to one another. A zipper according to claim 18 wherein said two grip strips (36, 36', 36'') on said second lip (34) intercept each other. A zipper according to one of claims 18 or 19 wherein said two grip strips (36, 36', 36'') on said second lip (34) are sinusoidal and offset from one another. A zipper according to one of claims 18 to 20 wherein said two grip strips (36, 36', 36'') on said second lip (34) are sinusoidal and offset from one another by 180°. A method of making a plastic bag with grip strips, comprising the steps of : providing a bag material with a pair of mating profiles (12, 14) ; moving said bag material in a first direction ; extruding at least two grip strips (36, 36', 36'') on said bag material through grip strip extruder outlet nozzles (40) ; characterized in that it further comprises the step of : additionally moving at least one of said grip strip extruder outlet nozzle (40) and said bag material with respect to one another whereby to provide an oscillating pattern to said grip strips (36) on said bag material, so that said two grip strips are shifted longitudinally with respect to one another. The method in accordance with claim 22 wherein said bag material is a film material. The method in accordance with claim 22 wherein said bag material is a zipper material. The method in accordance with one of claims 22 to 24 wherein said two grip strips (36, 36', 36'') intercept each other. The method in accordance with one of claims 22 to 25 wherein at least one of said grip strip extruder outlet nozzles (40) is moved with a reciprocating motion in a second direction transverse to the direction of movement of said bag material. The method in accordance with one of claims 22 to 26 wherein said bag material and mating profiles (12, 14) are extruded integrally. The method in accordance with one of claims 22 to 27 wherein at least two of said grip strips (36) are disposed between one of said profiles (12, 14) and a line (S-S) between said mating profiles (12, 14). The method in accordance with one of claims 22 to 28 wherein said grip strips extruder outlet nozzles (40) are longitudinally offset from one another in said first direction. The method in accordance with one of claims 22 to 29 wherein said first and second grip strips (36, 36') are generally sinusoidal and offset from one another by 180°. An apparatus for forming grip strips on a profiled film from which recloseable plastic bags are to be formed comprising ; means for moving said film along a first path ; grip strips extruder outlet nozzles (40) and characterized in that it further comprises : means for moving said outlet nozzles (40) relative to the film moving along said first path, so as to form at least two oscillating grip strips shifted longitudinally with respect to one another. The apparatus in accordance with claim 31 wherein said grip strips extruder outlet nozzles (40) are disposed for movement along a second path. The apparatus according to one of claims 31 or 32 wherein said means for moving said outlet nozzles (40) reciprocates said outlet nozzles (40) along said second path. The apparatus according to one of claims 31 to 33 wherein said second path is generally transverse to said first path. The apparatus according to one of claims 31 to 34 wherein said moving means is of variable speed. The apparatus according to one of claims 31 to 35 wherein said movement is directed along several paths simultaneously. The apparatus according to one of claims 31 to 36 wherein multiple grip strip extruder nozzles (40) move along different paths relative to the film path. The apparatus according to one of claims 31 to 37 wherein said two oscillating grip strips (36, 36', 36'') intercept each other. The apparatus according to one of claims 31 to 38 wherein said two oscillating grip strips (36, 36', 36'') are sinusoidal and offset from one another.

Inventors: AUSNIT STEVEN, AUSNIT, STEVEN
Applicants: MINIGRIP INC, MINIGRIP, INC.
Application year: 1993
Main classification: B65D33
IPC codes: B29C47, B65D33