End-Closure for a Flexible Tank

Abstract

A flexible tank has one or more inner layers and one or more outer layers enclosing the inner layers. It has an improved structure to prevent leakage and rupture when making a long multi-modal shipment of large quantities of a liquid, including when the flexible tank is not supported by the end or side walls of a shipping container.

Claims

1. A flexible tank for transporting bulk liquids or semi-liquid materials, comprising: an interior tank made of a flexible water-proof polymeric material. said interior tank being generally rectangular in shape with a width of at least one end of the interior tank being less than the length of the interior tank, the interior tank enclosing within it the bulk liquid or semi-liquid materials being transported; a first exterior layer made of a flexible polymeric material in a generally rectangular shape, a first end of the first exterior layer having a series of hollow loops and spaces between the hollow loops in a widthwise direction along the first end, the hollow loops and spaces alternating in sequence; a second exterior layer made of a flexible polymeric material in a shape and size substantially similar to the first exterior layer, a first end of the second exterior layer having a series of hollow loops and spaces between the hollow loops, the hollow loops and spaces alternating in sequence in the widthwise direction of the first exterior layer, the first end of the second exterior layer being matched up with the first end of the first exterior layer such that the hollow loops of the second exterior layer occur at the positions of the spaces of the first exterior layer and the spaces a the second exterior layer occur at the positions of the hollow loops of the first exterior layer; and a rope, the rope passing through the alternating hollow loops of the first and second exterior layers and connecting the first and second exterior layers to each other, the interior tank being constrained within the first and second exterior layers connected by the rope.

2. The flexible tank of claim 1, wherein said interior tank has multiple layers, at least one of said multiple layers of said interior tank being attached to said first exterior layer or said second exterior layer.

3. The flexible tank of claim 2, wherein said at least one of said multiple layers of said interior tank is attached to said first exterior layer or said second exterior layer by a weld.

4. The flexible tank of claim 3, wherein at least one of said multiple layers of said interior tank has a coupon or seam and said coupon or seam is folded inside of said first and second exterior layers.

5. The flexible tank of claim 1, wherein the hollow loops comprise folded over portions of the first and second exterior layers.

6. The flexible tank of claim i, wherein the spaces comprise cut-outs from the flexible polymeric material.

7. The flexible tank of claim 1, wherein the flexible tank is at least 20 feet in length.

8. The flexible tank of claim 1, wherein the flexible tank has a capacity of more than 8,000 liters.

9. A method of manufacturing a flexible tank for the transport of bulk liquids or semi-liquid materials, comprising: folding over the ends of rectangular shaped first and second layers of flexible polymeric material to form a continuous loop over the entirety of the width of said ends of said first and second layers; connecting the longitudinal sides of the first and second layers to form an open ended tube; attaching a first end of a first end flap to the inside of one of the first and second layers near a first end of the open ended tube and a first end of a second end flap to the inside of one of the first and second layers near a second end of the open ended tube, the length of the first end flap being greater than the distance from its point of attachment to the first end of the open ended tube and the length of the second end flap being greater than the distance from its point of attachment to the second end of the open ended tube; cutting portions from each one of the continuous loops of said ends of said first and second layers so as to become a sequence of alternating hollow loops and spaces, the hollow loops and spaces of the first layer interlacing with the hollow loops and spaces of the second layer; inserting an inner liner into the interior space of the open ended tube formed by connecting the longitudinal sides of the first and second layers, the inner liner made of a flexible water-proof polymeric material so as to enclose within it the bulk liquid or semi-liquid materials being transported; moving the respective second ends of the first and second end flaps to cover the ends of the inner liner; and closing the first and second ends of the flexible tank with the inner liner and end flaps constrained therein by, threading a rope between the interlaced hollow loops of the first and second layers.

10. A method of manufacturing a flexible tank as set forth in claim 9, further comprising the first and second end flaps being attached by a weld to one of the first and second layers.

11. A method of manufacturing a flexible tank as set forth in claim 10, further comprising the first and second end flaps being attached about 30 to 35 inches from the ends of the open ended tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIGS. 1 and 2 is a perspective view of a flexible tank in a partially cut-away shipping container.

[0009] FIGS. 3(a), 3(b), and 3(c) show aspects of a prior art flexible tank.

[0010] FIG. 4 is a perspective view of part of an end closure for a flexible tank according to one embodiment of the invention.

[0011] FIG. 5 shows an unassembled view of the components in the end closure of FIG. 4.

[0012] FIG. 6 shows a partially assembled view of the components in the end closure of FIG. 4.

[0013] FIGS. 7(a) to 7(e) show the steps of a preferred method of making a flexible tank.

[0014] FIG. 8 is a perspective view of part of the end closure of FIG. 4 when the flexible tank is filled with liquid.

[0015] FIG. 9 is a perspective view of an optional baffle that may be used with a flexible tank.

[0016] FIG. 10 is a side view of the baffle in FIG. 9.

[0017] FIGS. 11 and 12 show the ends of the baffle in FIG. 9.

DETAILED DESCRIPTION

[0018] An embodiment of a flexitank is shown in the accompanying figures. FIGS. 1 and 2 show a flexitank resting on the floor of a standard shipping container (horizontal cut away view). The flexitank is shorter than the internal length of the shipping container and its ends fall short of the end walls of the container.

[0019] An external cover provides additional strength along the length of the flexitank that will absorb and control the internal liquid dynamics during transport. The external cover for the flexitank is preferably constructed from layers of a 610 gram per square meter vinyl fabric on a base reinforcing scrim of either a 14×14 or 20×20 per centimeter polyester thread. Such a relatively high thread count of the scrim provides added strength for the carriage of liquids with a specific gravity higher than water. The diameter of the covering external layers is dependent on the required capacity of the flexitank.

[0020] The flexitank external cover may or may not have the end closures shown in FIGS. 4-8, but it does seal both ends of the inner tank and provides additional strength to the heat sealed end seams of the inner tank when compared to the sewn ends shown in FIGS. 3(a) to 3(c), preventing any bursting of the of the seam when under pressure from the liquid forces placed upon it. The result is a flexitank that is overall much stronger than the conventional flexitank.

[0021] A process of forming a flexitank according to one embodiment of the invention is shown in FIGS. 7(a)-7(e).

[0022] In the first step, long and narrow fabric layers are welded together longitudinally, preferably by radio frequency (RF) welding, to form the top and bottom layers of the external cover. The ends of the top and bottom layers are welded back onto itself as shown in FIG. 7(a) to form a loop sufficiently large to accept a reinforcement, such as a nylon rope.

[0023] In the second step, an end flap is preferably welded to the inside of the bottom layer about 30 to 36 inches from each end of the bottom layer. This end flap may be the same fabric as the top and bottom outer layers. The end flap has the same width as the top and bottom layers and a length of approximately 7 to 8 feet. At this point, the end flap extends past the end of the bottom layer as shown by dashed line A in FIG. 7(b). When manufacture of the flexitank is complete, the end flap will be positioned as shown by dashed line B in FIG. 7(b). The end flap provides additional reinforcement at the crucial area where the inner tank contacts the ends of the external cover. It is to be understood that, although not shown in the cross-section view, the longitudinal sides of the top and bottom layer of the external cover are welded to each other so as to form an open ended tube.

[0024] In the third step, the looped ends of the top and bottom layers of the external cover are cut at the same points to form corresponding equal sized sections of the looped ends as shown in FIG. 7(c). Odd loops are removed from one of the layers and even loops are removed from the other layer so that the layers have alternating interlaced loops in the manner of a door hinge. The number of loops is dependent on the width and, preferably, each loop is 6 centimeters long. The loops are positioned in such a way that in a lay-flat position, the loops of the top and bottom external layers will be adjacent to and alternating with each other in an interlaced manner. See FIGS. 4-6.

[0025] In the fourth step, a top mounted load/discharge valve is attached to the inner tank through an opening on the top layer of the external cover centrally placed widthwise and near one end seam lengthwise, preferably about 30 to 36 inches from the end. The valve is preferably secured using a clamp. The inner tank, with its 2-4 layers already formed and welded together at the ends, is inserted through the open end of the external cover nearer the valve and positioned between the top and bottom layers. As shown in FIGS. 7(d) and 7(e), an additional liner having a length substantially the same as the end flap of the external cover is attached to the ends of the inner tank, but not by welding. This additional liner is preferably the same as the layers of the inner tank, especially if the layers of the inner tank are clear plastic layers. Any “coupon” of the inner tank liner at the closed end of the bag is tucked so that it lays flat against the layers of the external cover. Any “coupon” of the inner tank liner at the open end of the bag is tucked and then the end flap of the exterior cover is moved from the position of dashed line A in FIG. 7(b), so as to cover the end and the coupon of the inner liner as shown in FIG. 7(d) and be positioned over the top of the inner tank liner. Although both are shown in the drawings, another embodiment may have only one or the other of the inner tank liner and the external cover end flap. Also, although illustrated with end closures of loops and rope, the inner tank liner and/or end flap of the external cover may be used with end closures other than those shown in the drawings.

[0026] In the final step, a nylon rope or similar securing element is threaded through the alternating interlaced loops of the open ends of the bag completely across the seams. The rope closes the seams and secures the flexitank into the cover. When the inner tank is filled with liquid as shown in FIG. 7(e), the inner tank liner expands pushing against the end flap and against the end closures. It is to be noted that the end closures of the external cover are not watertight and are not intended to be watertight. The end flap provides some protection against leakage but primarily provides additional strength to the end closure. The end flap contains the inner liner inside the external layers of the cover, stopping it from coming into direct contact with the end closure. As shown in FIG. 8, the loops do not remain in alignment and the rope does not remain straight when the flexitank is filled, but they do provide end-closures of significant strength. The rope can be secured in any suitable fashion to keep the end closures closed, and the ends of the rope may be attached, such as to a shipping container, so as to impede movement of the flexible tank, during shipment.

[0027] The flexitank is preferably kept relatively low in height. Two or three baffles, external to the flexitank, can optionally be installed in the shipping container to restrict waves during transit. The baffles offer low height channels (for example, from 2-4 inches) for the liquid to flow through and effectively divide a single liner into three or four sections. This controls the liquid dynamics of the liquid and thus reduces dynamic loading on the end-closures of the flexitank. The baffles may be constructed and secured to the container in any suitable manner. Although a shipping container may have the baffles welded or otherwise permanently installed, the presence of the baffles may be a detriment when the container is being used to transport goods without a flexitank. It is preferable that the external baffles may be easily installed in a standard shipping container when a flexitank is used and removed after use. A preferred example of a removable baffle is the compression bar shown in FIGS. 9-12 that locks between the container side walls. One end of the compression bar has the cam system and shoe shown in FIG. 11 and the other end has the shoe shown in FIG. 12. The shoes preferably have metal housings and contact surfaces made of a rubber, and can pivot to accommodate deflection of the container walls under stress. The cam system is accessible by a hole in the top of the compression bar and engaged by a socket drive to move the end of the compression bar in the horizontal direction to lock it into position.

[0028] A flexible tank having an end closure according to the invention may vary in multiple ways from the precise description provided herein. In particular, the flexitank with the end closure may be used without the optional baffles and may be used independently of a shipping container. The extra strength provided by the end closure may permit a flexible tank to be used in a variety of industries, purposes, circumstances, and environments not specifically identified herein.