WO1991013759A1

WO1991013759A1 - Method of assembling a multipart plastic slider with a plastic reclosable fastener by ultrasonic welding

Info

Publication number: WO1991013759A1
Application number: PCT/US1991/001371
Authority: WO
Inventors: Fox John Herrington
Original assignee: Mobil Oil Corporation
Priority date: 1990-03-07
Filing date: 1991-02-27
Publication date: 1991-09-19

Abstract

A method of assembling a multipart plastic slider (10) with a profiled plastic reclosable fastener (14, 15) on plastic bags (12) by ultrasonic welding is disclosed. The multipart plastic slider (10) includes at least two parts ultrasonically welded in place on the plastic bags (10).

Description

METHOD OF ASSEMBLING A MULTIPART PLASTIC SLIDER WITH A PLASTIC RECLOSABLE FASTENER BY ULTRASONIC WELDING

The present invention relates to improvements in plastic sliders for opening and closing plastic reclosable fasteners on plastic bags and the like and the method of assembling a multipart plastic slider with a profiled plastic reclosable fastener on the plastic bags by ultrasonic welding.

Zippers with sliders are made commercially in several forms. The most common ones used on clothing have teeth which interlock. The teeth may be made of metal or plastic. Other types of plastic zippers have profiles that include a pair of male and female fastener elements in the form of reclosable interlocking rib and groove elements with a slider for opening or closing the rib and groove elements. In the manufacture of thermoplastic film bags, a pair of these male and female fastener elements extend along the mouth of the bag and these male and female elements are adapted to be secured in any suitable manner to the flexible walls of the thermoplastic film bag. These elements may be integral marginal portions of such walls or they may be extruded separately and thereafter attached to the wall along the mouth of the bag. A method of continuously providing such a fastener on the thermoplastic film is disclosed in U.S. patent 3,462,332.

The sliders for opening or closing the reclosable fasteners are essentially U-shaped and adapted to be assembled with the fastener or zipper by an endwise assembly or by a relative transverse maneuver. Where the assembly is performed by a relative transverse maneuver the slider is normally molded from a semi-hard plastic where there is enough yieldability in the side walls of the slider to provide sufficient flexibility to enable spreading apart of the terminal portions of the side walls of the slider so as to clear the interlocking rib and groove elements to permit assembly of the slider with the zipper by relative transverse movement. Where the slider is formed from a metal die casting or a hard plastic, it has been necessary to rely upon the elastic deformation of the plastic zipper elements to permit the transverse assembly movement of the slider. Such assembly can cause damage to the interlocking rib and groove elements during assembly and leaves something to be desired. Examples of assembly of sliders with plastic reclosable fasteners are disclosed in U.S. patents 3,426,396, 3,660,875, 3,713,923, 3,790,992 and 3,806,998.

A method of assembling a plastic slider with a plastic reclosable fastener is disclosed in my related application entitled "Method of Assembling a Snapped-Together Multipart Plastic Slider with a Plastic Reclosable Fastener" Attorney Docket 5155 filed concurrently herewith. It is an object of the present invention to provide a new and improved multipart plastic zipper slider and method of assembling the same with a profiled plastic reclosable fastener by ultrasonic welding without deforming the fastener during assembly of the slider therewith.

The present invention relates to a multipart plastic slider for a profiled plastic reclosable fastener particularly suited for thermoplastic bags and the like formed by a pair of flexible plastic sheets having a top edge with separable fastener means extending along the length thereof comprising reclosable interlocking rib and groove profile elements on the respective sheets. A straddling slider for closing or opening the reclosable fastener elements is provided comprising an inverted U-shaped plastic member having a back for moving along the top edges of the fastener elements with depending side walls projecting therefrom and extending from an opening end of the slider to a closing end, the side walls being spaced wider apart at the opening end to permit separation of the rib and groove elements and being spaced sufficiently close together at the closing end to press the rib and groove elements into interlocking relationship as the slider is moved in a fastener closing direction. A depending plastic separator finger is provided on the slider extending between the side walls of the opening end for separating the rib and groove elements as the slider is moved in a fastener opening direction, the separating finger being of wedge-shaped construction with the wider end of the wedge at the opening end. Shoulder structure is provided on the bottom of the separator finger interengaging the bottom of the fastener for preventing the slider from being lifted off the top edge of the fastener while the slider straddles the fastener. In one form of the invention, the inverted U-shaped member and the separating finger are ultrasonically welded together on the fastener and the lower end of the separating finger has outwardly extending shoulder structure for engaging the bottom of the fastener to prevent the slider from being lifted off the top edge of the fastener while the slider straddles the fastener. In another aspect of the invention, the upper ends of the side walls of the inverted U-shaped member are ultrasonically welded to the back which is integral with the depending separator finger having at its bottom end shoulder structure for interengaging the fastener to prevent the slider from being lifted off the top edge of the fastener while the slider straddles the fastener.

It is a further object of the invention to provide a method of assembly of a multipart plastic slider in straddling relation with a profiled plastic reclosable fastener particularly suited for thermoplastic bags and the like formed by a pair of flexible plastic sheets having a top edge with separable fastener means extending along the length thereof comprising reclosable interlocking rib and groove profile elements on the respective sheets, the straddling slider for closing or opening the reclosable fastener elements comprising a wedge-shaped separator finger and complimentary structure formed from plastic for moving along the fastener, the complimentary structure including depending side walls extending from an opening end of the slider to a closing end, the side walls being spaced wider apart at the opening end to permit separation of the rib and groove elements by the wedge-shaped separator finger extending between the side walls at the opening end, the side walls being spaced sufficiently close together at the closing end to press -_he rib and groove elements into interlocking relationship as the slider is moved in a fastener closing direction, the separator finger having shoulder structure on the bottom of the finger for engaging the bottom of the fastener. The method comprises the steps of placing the interlocking rib and groove profile elements in facing alignment so that they can be joined, supporting the wedge-shaped separator finger between the rib and groove profile elements with the shoulder structure on the bottom of the finger aligned to engage the bottom of the fastener, pressing the rib and groove profile elements together so that the profiles are interlocked at the location adjacent to the closing end of the slider and against the sides of the wedge-shaped separator finger, positioning the complimentary structure of the slider for assembly with the top end of the finger, assembling the complimentary structure of the slider in a direction transversely of the rib and groove profile elements so that the side walls straddle the rib and groove profile elements of the fastener, and thereafter ultrasonically welding the wedge-shaped separator finger to the complimentary structure so that the shoulder structure thereon engages the bottom of at least one of the rib and groove profile elements to prevent the slider from being lifted off the top edge of the fastener while the slider straddles the fastener.

It is a further object of the invention to provide a method of assembly of a multipart plastic slider comprising a separator finger and complimentary ₀ structure with a profiled plastic reclosable fastener particularly suited for thermoplastic bags for opening and closing the fastener. The method comprises the steps of positioning a plastic bag having a plastic reclosable fastener along the top edges of the front ₅ and back faces of the bag to receive the multipart plastic slider in straddling relation, the fastener having a female fastener profile attached to one of the faces of the bag and a male fastener profile attached to the other face of the bag. The method further o includes inserting the plastic separator finger between the male and female profiles, and forming the slider in straddling relation around the male and female fastener profiles on the bag by ultrasonically welding together the plastic separator finger and the complimentary ₅ structure whereby movement of the slider in one direction opens the fastener and movement in the opposite direction recloses the fastener. In one aspect of the invention the separator finger includes a wedge-shaped portion and a bottom member supporting the _Q wedge-shaped portion and engaging the bottom of the male and female fastener profiles and the complimentary structure comprises an inverted U-shaped member sealed to the top end of the wedge-shaped portion of the separator finger. In another aspect of the invention, 5 the separator finger includes an I-shaped section and the complimentary structure comprises a pair of side members sealed to the top edges of the I-shaped section. In another aspect of the invention the separator finger includes a T-shaped section and the complimentary structure comprises a pair of side members sealed to the top edges of the T-shaped section and shoulder structures in the side members for cooperating with the bottom of the male and female fastener profiles to maintain the slider on the fastener.

Other objects and advantages of the invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings.

Fig. 1 is a perspective view of a thermoplastic bag or the like having a multipart plastic slider embodying the present invention assembled on the separable fastener means at the top edge of the bag in accordance with the method embodying the present invention.

Fig. 2 is a fractional top plan view on enlarged scale of the slider shown in Fig. 1.

Fig. 3 is a sectional view taken along the lines 3-3 in Fig. 2.

Fig. 4 is a sectional view taken along the lines 4-4 in Fig. 2. Fig. 5 is a sectional view taken along the lines 5-5 in Fig. 2.

Fig. 6 is exploded view illustrating the method of assembling the multipart plastic slider of Figs. 1 and 2 by ultrasonic welding with the profiled plastic reclosable fastener in accordance with the present invention.

Fig. 7 is a perspective view of the multipart plastic slider assembled according to Fig. 6.

Figs. 8 is an exploded view of the method of assembly of a modification of a multipart plastic slider embodying the present invention. Fig. 9 is a perspective view of the assembled multipart plastic slider of Fig. 8.

Fig. 10 is an exploded view of the method of assembly of a further modification of a multipart plastic slider embodying the present invention.

Fig. 11 is a perspective view of the assembled multipart plastic slider of Fig. 10.

Referring to Fig. 1, there is illustrated a multipart plastic slider 10 for a profiled plastic reclosable fastener embodying the present invention.

The slider 10 is particularly suited for thermoplastic bags and the like and has been illustrated in Fig. 1 in connection with a thermoplastic bag 11. The bag 11 may be made from any suitable thermoplastic film such for example as polyethylene or polypropylene or equivalent material. The bag 11 is formed by a pair of flexible plastic sheets 12 and 13 having a top edge with separable fastener means at the top edge extending along the length thereof having reclosable interlocking rib and groove profile elements 14 and 15 on the facing surfaces thereof. As pointed out above, in the manufacture of thermoplastic film bags, the pair of male and female fastener elements 14 and 15 extend along the mouth of the bag and these (interlocking rib and groove profiles) elements are adapted to be secured in any suitable manner to the flexible walls of the thermoplastic film bag. These elements may be integral marginal portions of such walls or they may be extruded separately and thereafter attached to the walls along the mouth of the bag as well known in the art. The elements 14 and 15 are attached to the respective walls of the bag on opposite sides of the bag as disclosed in Figures 3-8. The manner of attaching these elements to the respective walls of the bag is well known in the art and does not form part of the present invention. As may be seen in Figs. 1, 2 and 7 the slider 10 straddles the reclosable fastener elements at the top of the berg 11 and is adapted for opening or closing the reclosable fastener elements. The fastener 10 is formed from multiple plastic parts comprising a separator finger and complimentary structure. The plastic parts are molded from a plastic that can be ultrasonically welded such for example as nylon, polypropylene, polystyrene, Delrin or ABS. In the preferred embodiment the complimentary structure comprises, an inverted U-shaped member having a back 20 for moving along the top edges of the fastener elements with integral depending side walls 21 and 22 projecting therefrom and extending from an opening end 10a of the slider to a closing end 10b. As may be seen in Figs. 2-5 the side walls 20 and 21 are spaced wider apart at the opening end 10a of the slider 10 to permit separation of the rib and groove elements 14 and 15 and are spaced sufficiently close together at the closing end 10b of the slider to press the rib and groove elements 14 and 15 into interlocking relationship, Fig. 5, as the slider 10 is moved in a fastener closing direction.

The slider 10 is provided with a depending plastic separator finger 24 which extends between the side walls 21 and 22 at the opening end 10a of the slider 10 for separating the rib and groove elements 14 and 15 as the slider 10 is moved in a fastener opening directions, Fig. 2 and 3. As may be seen in Figs. 2 and 3, the separating finger 24 is of wedge-shaped construction with the wider end 24a of the wedge 24 at the opening end 10a of the slider 10. The separating finger is provided at its lower end with outwardly extending shoulder structure 24b, Figs. 2-4 for engaging the bottom of the fastener comprising the rib and groove elements 14 and 15 to prevent the slider 10 from being lifted off the top edge of the fastener while the slider straddles the fastener as shown in Figs 1-3. -9-

Referring to Figs. 6-7 there is illustrated the method of assembling the multipart plastic slider 10 with the profiled plastic reclosable fastener of a thermoplastic bag formed by the pair of flexible

5 plastic sheets 12 and 13 having a top edge with separable fastener means at the top edge extending along the length thereof having reclosable interlocking rib and groove profile elements 14 and 15 on the facing surfaces thereof. The interlocking rib and groove

1₀ profile elements 14 and 15 on the facing surfaces are placed in alignment so that they can be joined as indicated at the right hand end of Fig. 2. The wedge-shaped separator finger 24 is supported as by member 25 between the rib and groove profile elements

15 14 and 15 with the shoulder structure 24b on the bottom of the finger aligned to engage the bottom of the fasteners. The separator finger 24 may be supported below or from above as desired. The rib and groove profile elements 14 and 15 are then pressed together so

20 that the profiles are interlocked at the location adjacent the closing end 10b of the slider and against the sides of the wedge-shaped separator finger 24. The inverted U-shaped part 20-22 of the slider 10 is then positioned above the profile elements 14, 15, Fig.

25 6, for assembly thereon. The rib and groove profile elements 14 and 15 are maintained apart and separated from each other at the location adjacent to the opening end 10a of the slider. The slider 10 is then assembled by moving the inverted U-shaped member in a

30 direction transversely of the rib and groove profile elements 14 and 15 so that the side walls 21 and 22 straddle the rib and groove profile elements 14 and 15 and the back 20 of the inverted U-shaped member rests along the top edges of the fastener elements and on the

35 top end of the wedge-shaped member 24 without deforming the rib and groove elements 14 and 15 of the fastener 10. The top end of the wedge-shaped finger 24 is then ultrasonically welded by any suitable known technique to the bottom of the back 20 of the inverted U-shaped member as shown in Fig. 7 so that the shoulder 24 engages the bottom of at least one of the rib and groove profile elements 14 and 15 to prevent the slider 10 from being lifted off the top edge of the fastener while the slider straddles the fastener.

By making the slider 10 of multiple plastic parts, the slider can be readily assembled in a transverse direction with the rib and groove profile elements by inserting the finger 24 between the rib and groove profile elements and ultrasonically welding it to the back 20 of the slider while it engages the top edge of the bag. This is accomplished without deforming the rib and groove elements of the fastener thereby eliminating any possible damage to these elements and also enables the assembly of the slider with the elements of the fastener to be accomplished quickly and insures that the assemble is accomplished properly. Referring to Figs. 8 and 9 there is illustrated a modification of the present invention. In this modification the slider 10' is similar to the slider 10 previously described with certain exceptions. In the slider 10' the back 20' of the inverted U-shaped member is integral with the separator finger 24' and the shoulder structure 24a¹ to form an I-shaped section. The side walls 21* and 22' are separate members which are adapted to be ultrasonically welded to the edges of the back 20' at the top end of the separator finger 24'. Thus as may be seen in Fig. 8 the wedge-shaped separator finger 24' is supported by the member 25 between the rib and groove profile elements 14 and 15 with the shoulder structure 24b' on the bottom of the finger aligned to engage the bottom of the fastener and the back 20' of the U-shaped member aligned with the top edge of the bag structure. The rib and groove profile elements 14 and 15 are pressed together so that -li¬

the profiles are interlocked at the location adjacent the closing end 10b¹ of the slider and against the sides of the wedge-shaped separator finger 24' . The side walls 21' and 22' are pressed against the side edges of the back member 20' and ultrasonically welded thereto as shown in Fig. 9. The side members 21' and 22' may be positioned against the edges of the back member 20* by any suitable means such for example as the plungers 26 and 27 illustrated in Fig. 8. After the ultrasonic welding has been completed, the plungers 26 and 27 are withdrawn so that the slider 10* is assembled with the profiled plastic reclosable fastener as illustrated in Fig. 9.

Referring to Figs. 10 and 11 there is illustrated a further modification of the present invention. In this modification the slider 10" is similar to the slider 10' previously described with certain exceptions. In the slider 10" the back 20" of the inverted U-shaped member is integral with the separator finger 24" but the shoulder structure 24a¹ in Fig. 9 is omitted to form a T-shaped section and added to the side walls 21" and 22" at the bottom thereof as shoulders 21a" and 22a". The side walls 21" and 22" are separate members which are adapted to be ultrasonically welded to the edges of the back 20" at the top end of the separator finger 24". Thus as may be seen in Fig. 10 the wedge-shaped separator finger 24" is T-shaped and supported by the member 25 between the rib and groove profile elements 14 and 15 with the back 20" of the U-shaped member aligned with the top edge of the bag structure. The rib and groove profile elements 14 and 15 are pressed together so that the profiles are interlocked at the location adjacent the closing end 10b" of the slider and against the sides of the wedge-shaped separator finger 24". The side walls 21" and 22" are pressed against the side edges of the back member 20" and ultrasonically welded thereto as shown in Fig. 11. The shoulders 21a" and 22a" are positioned beneath the bottom of the fastener elements 24 and 15 to prevent the slider 10" from being lifted off the top edge of the fastener. The side members 21" and 22" may be positioned against the edges of the back member 20" by any suitable means such for example as the plungers 26 and 27 illustrated in Fig. 10. After the ultrasonic welding has been completed, the plungers 26 and 27 are withdrawn so that the slider 10" is assembled with the profiled plastic reclosable fastener as illustrated in Fig. 11. While the shoulder 24b at the, bottom end of finger 24" has been omitted in Figs. 10 and 11, it can be added to assist the shoulders 21a" and 22a" in keeping the slider 10" on the fastener. The method of assembly disclosed herein is particularly suited for the manufacture of thermoplastic bags on a production line where the bags move sequentially along the production line. The multipart plastic sliders 10, 10* and 10" may be assembled with the bags prior to the formation of the side seals or after the formation of the side seals and severing of the individual bags as desired. In any event the multipart plastic sliders are assembled with the reclosable fastener structure at periodic intervals along the plastic profiles with one fastener for each bag to be manufactured.

Claims

Claims ;

1. The method of assembly of a multipart plastic slider in straddling relation with a profiled plastic reclosable fastener particularly suited for thermoplastic bags and the like formed by a pair of flexible plastic sheets each having a top edge with separable fastener means extending along the length thereof comprising reclosable interlocking rib and groove profile elements on the respective sheets, the straddling slider for closing or opening the reclosable fastener elements comprising a wedge-shaped separator finger and complimentary structure formed from plastic for moving along the fastener, the complimentary structure including depending side walls extending from an opening end of the slider to a closing end, the side walls being spaced wider apart at the opening end to permit separation of the rib and groove elements by the wedge-shaped separator finger extending between the side walls at the opening end, the side walls being spaced sufficiently close together at the closing end to press the rib and groove elements into interlocking relationship as the slider is moved in a fastener closing direction, the separator finger having shoulder structure on the bottom of the finger for engaging the bottom of the fastener, the method comprising the steps of placing the interlocking rib and groove profile elements in facing alignment so that they can be joined, supporting the wedge-shaped separator finger between the rib and groove profile elements with the shoulder structure on the bottom of the finger aligned to engage the bottom of the fastener, pressing the rib and groove profile elements together so that the profiles are interlocked at the location adjacent the closing end of the slider and against the sides of the wedge-shaped separator finger, positioning the complimentary structure of the slider for assembly with the top end of the finger, assembling the complimentary structure of the slider in a direction transversely of the rib and groove profile elements so that the side walls straddle the rib and groove profile elements of the fastener, and thereafter ultrasonically welding the wedge-shaped separator finger to the complimentary structure so that the shoulder structure on the bottom of the wedge-shaped finger engages the bottom of at least one of the rib and groove profile elements to prevent the slider from being lifted off the top edge of the fastener while the slider straddles the fastener.

2. The method according to claim 1 wherein the complimentary structure comprises an inverted U-shaped member sealed to the top end of the wedge-shaped separator finger.

3. The method according to claim 1 wherein the separator finger includes an I-shaped section and the complimentary structure comprises a pair of side members sealed to the top edges of the I-shaped section.

4. The method of assembly of a multipart plastic slider comprising a separator finger and complimentary structure, with a profiled plastic reclosable fastener particularly suited for thermoplastic bags for opening and closing the fastener comprising: positioning a plastic bag having a plastic reclosable fastener along the top edges of the front and back faces of the bag to receive the multipart plastic slider in straddling relation, the fastener having a female fastener profile attached to one of the faces of the bag and a male fastener profile attached to the other face of the bag, inserting the plastic separator finger between the male and female profiles, and forming the slider in straddling relation around the male and female fastener profiles at the top edges of the bag by ultrasonically welding together the plastic separator finger and the complimentary structure whereby movement of the slider in one direction opens the fastener and movement in the opposite direction recloses the fastener.

5. The method according to claim 4 wherein the separator finger includes a wedge-shaped portion and a shoulder portion at the bottom end thereof for engaging the bottom of the male and female fastener profiles.

6. The method according to claim 5 wherein the complimentary structure comprises an inverted U-shaped member sealed to the top end of the wedge-shaped portion of the separator finger.

7. The method according to claim 4 wherein the separator finger includes an I-shaped section and the complimentary structure comprises a pair of side members sealed to the top edges of the I-shaped section.

8. The method according to claim 4 wherein the separation finger includes a T-shaped section and the complimentary structures comprises a pair of side members sealed to the top edges of the T-shaped section and shoulder structures on the side member for cooperating with the bottom of the male and female fastener profile to maintain the slider on the fastener.

9. A plastic bag and plastic slider assembled according to the method of claim 4.

F5154/1991A