Closure Device For Plastic Bags

Abstract

A closure device for plastic bags or sacks formed as a one-piece body of molded plastic and comprises a plate with upper and lower portions and an elongate slot provided therebetween, cooperating latching elements arranged in the portions for latching engagement with one another, and hinges disposed at the ends of the elongate slot connecting the portions of the plate to each other. Projections extending from the facing edges of the plate portions at the hinges for limiting the pivoting zone of the hinge and therefore facilitating the alignment of the latching portions in bringing them into latching position. A tear-away guarantee strip may be provided to seal the elongate slot requiring its removal to gain access to the interior of the bag or sack.

Description

BACKGROUND OF THE INVENTION

The present invention relates to closure devices for bags or sacks in particular plastic bags or sacks.

Generally such closure devices comprise two separate parts welded to the opening of the bag or sack and include weld reinforcements in the form of metal clips which strengthen the side edges to prevent the side of the bag or sack from tearing when the bag is opened or during handling of the bag or sack.

Other closure devices for such bags have been found difficult to maintain in closed position during carrying owing to stresses acting thereon.

SUMMARY OF THE INVENTION

An object of the present invention is a closure device for such bags which overcomes above-mentioned disadvantages.

To this end the present invention provides a one-piece or unitary closure device, preferably formed of plastic, which have hinge means of a reduced section which do not in normal use urge a force on the latching member of the closure device which could effect their opening.

Further, these hinge means are associated with means for limiting the zone of pivoting to thereby facilitate the alignment of the latching elements on closing. The hinge means according to the invention offers considerable resistance to tearing both during the latching and unlatching operations as well as the separating of the portions of the plate to gain access to the interior of the bag.

A more particular object of the invention is a unitary closure device for a bag comprising : a plate having first and second portions, an elongate means adapted to provide access to the interior of the bag and disposed between the first and second plate portions, at least one latching element on one of the plate portions adapted to engage a cooperating latching element on the other of the portions for maintaining the closure device in a closed position preventing access to the elongate means, and hinge means connecting the plate portions at the ends of the elongate means for pivotably mounting said first portion relative to said second portion, said hinge means having a thickness substantially less than that of the plate, and means for limiting the pivoting zone of the hinge for facilitating the alignment of latching elements on closing the device.

According to a further object of the invention the means for limiting the zone of pivoting comprises opposed pairs of projections extending from the plates towards each other and disposed at the hinge means spaced from the elongate means.

According to a still further object of the invention the elongate means comprises a tear-away strip sealingly arranged between the portions of the plate and adapted to be removed to expose an elongate slot between the hinge means and the plates.

Further, such a closure device may simply be manufactured in one piece by injection molding of plastic such a polyvinylchloride ; the bag with which it is to be associated being attached thereto by welding.

Additional features and advantages of the present invention will be brought in the description which follows hereinbelow by way of example with references to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view in perspective of a closure device for a plastic bag according to the invention in its unlatched position ;

FIG. 2 shows a view in perspective of the closure of FIG. 1 in its latched position ;

FIG. 3 shows a detail on an enlarged scale and in perspective of the hinge and cooperable latching elements shown in FIG. 1 ;

FIG. 4 shows a slightly enlarged cross-section of the closure device of FIG. 1 taken along the line IV--IV ;

FIG. 5 shows a slightly enlarged cross-section taken along the line V--V of FIG. 1 ;

FIG. 6 shows a cross-section taken along the line VI--VI in FIG. 2 ;

FIG. 7 shows a schematic view in perspective of the bag opened giving access to the interior ;

FIG. 8 shows a view in perspective of an alternative embodiment of the closure device according to the invention in its sealed condition ;

FIG. 9 shows a view in perspective of the embodiment shown in FIG. 8 with the tear-away strip in the process of being removed ;

FIG. 10 shows a cross-section of the closure plate taken along the line X--X in FIG. 8 ;

FIG. 11 shows an enlarged cross-section of a detail of FIG. 10 ; and

FIG. 12 shows a view in section of an alternative tear-away strip to that shown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Considering first the embodiment of FIGS. 1-7 a unitary or one-piece closure device 10 formed of relatively rigid plastic material, for example polyvinylchloride, is provided on a bag or sack 12 formed of a relatively thin plastic sheet material. The bag or sack preferably comprises a front sheet 14 welded along its edges to a rear sheet 16. The bag or sack could however be formed of a continuous pouch with no welds or seams.

The front and rear sheets 14 and 16 are in turn welded at 17 and 18 to the lower portion 20 and the upper portion 22 of the closure device or plate 10. An elongate slot extends between the upper and lower portions 20 and 22 along substantially their entire lengths. Hinges 28 are provided at the ends of the slot 24, one of which is shown in detail in FIG. 3. A projecting latching member 25 with a slightly enlarged head portion 25a extends from the lower portion 20 and is adapted to be received in receiving aperture 26 provided in the upper portion 22 and suitable arranged and dimensioned to receive and maintain the projecting portion in the closed portion as illustrated in FIGS. 2 and 6, the diameter of head 25a being slightly larger than the diameter of the aperture 26.

The hinges 28 disposed at the ends of the elongate slot 24 have a thickness equal to approximately one-half the thickness of the adjacent plate portions 20 and 22. This hinge thickness is such as to maintain the two portions of the plate in generally the same plane in the unlatched position in order to give unhindered access to the opening formed by the slot 24, see FIG. 7. Each of the hinges 28 includes a relatively wide portion 30 having substantially the same width as the elongate slot 24 and a relatively narrow portion 32 defined between the inwardly directed pairs of projections 20a and 22a provided at the faced edges of the portions 20 and 22. The projections taper slightly towards the front face of the plate and have rounded corners to avoid stress concentrations. By the use of such a hinge a great degree of bending flexibility is provided while at the same time providing an accurately defined folding or pivoting zone in the portion 32 between the projections 20a and 22a such that on folding the upper portion 22 into the position shown in the FIG. 2 cooperating latching elements 25 and 26 are automatically aligned enabling a great facility in latching the closure device. The head 25a maintains the portions 20 and 22 in engagement as shown in FIG. 6 until it is desired to re-open the bag. In such a case the operation in reversed and the portions are pulled apart by aid of the handle or tab 36 fixed to the edge of the upper portion 22.

In order to have full access to the interior of the bag or sack, the portions 20 and 22 pivot or twist about the hinges 28 in a plane substantially perpendicular to the plane of the pivoting action described relative to latching. This twisting action is facilitated by the wide portion 30 of the hinge which is subject to the greatest stresses; accordingly, this construction tends to prevent a large shear stress concentration at the narrow portion 34 of the hinges which could cause severing along the folding or pivoting line.

A variation of this embodiment is shown in FIGS. 8-12 in which the closure element is provided with a guarantee strip.

Such a strip is intended to seal the elongate slot in the plate. Accordingly, the interior of the bag or sack forms a closed space and in order to have access to it the guarantee strip must be partially or completely undone thereby indicating this fact. Such an embodiment has obvious applications in the sale of retail goods.

Elements similar to those of the preceding embodiment are designated by the same numerals. As noted above, the slot between the upper and lower portions 20 and 22 is replaced by an elongate tear-away strip 40. In order to have access to the interior of the sack the tab 43 is pulled and the strip 40 is severed from the adjacent portions 20 and 22 along the lines 42 of reduced strength which are easily severed by this action. It should be noted that the tab 36 acts also as a handle before the removal of the guarantee strip.

In the cross-section of FIG. 11, the strip 40 is shown with a convex front surface and a flat rear surface in the plane of the rear surface of the plate 10. A variation of the cross-section of the tear-away strip 40' is shown in FIG. 12 in which both faces of the strip are convex which come together along lines of reduced section or strength 42'. The lower portion 22 is provided with an extension 45 with a slot therein. Such an extension enables the bag to be hung up or hooked onto an appropriate support.

The present invention is not intended to be limited by the embodiments described hereinabve but extends to all equivalents and variations with the scope of the appended claims.

Claims

I claim:

1. A unitary closure device for a bag comprising: a plate having a first and second portions, an elongate means adapted to provide access to the interior of the bag and disposed between the first and second plate portions, at least one latching element on one of the plate portions adapted to engage a cooperating latching element on the other of the portions for maintaining the closure device in a closed position preventing access to the elongate means, and hinge means connecting the plate portions at the ends of the elongate means for pivotably mounting said first portion relative to said second portion, said hinge means having a thickness substantially less than that of the plate, and interengaging projections on the plate portions adjacent the hinge means to align the latching elements on closing the device.

2. A closure device according to claim 1, wherein the width of the hinge means is greater adjacent to the elongate means than between pairs of projections.

3. A closure device according to claim 2, wherein the hinge means flares out from the projections to the adjacent edges of the plate.

4. A closure device according to claim 1, wherein the elongate means is an elongate slot defined between the hinges and the portions of the plate.

5. A closure device according to claim 1, wherein the elongate means comprises a tear-away strip sealingly arranged between the portions of the plate and adapted to be removed to expose an elongate slot between the hinge means and the plates.

6. A closure device according to claim 5, wherein the tear away strip includes a tab generally at one end thereof for facilitating its removal.

7. A closure device according to claim 1, wherein one of the portions of the plate is provided with means for hanging the bag.

8. A closure device according to claim 1, wherein the latching element comprises a projection with an enlarged head extending from the first portion of the plate, and the cooperating latching element comprises an aperture having a diameter slightly less than that of the head of the associated projection.

9. A closure device according to claim 1, wherein the portion of the plate adapted to be pivoted includes a tab for facilitating the unlatching of the closure device.

10. A closure device according to claim 1, wherein one face of the associated bag is adapted to be connected to the rear face of the first plate portion and to the front face of the second plate portion.