Title:
Dunnage bag
United States Patent 3868026


Abstract:
A dunnage bag provided with two sheets of flexible material interposed between the walls of the bladder adjacent the air inlet to the bladder. The sheets of flexible material protect the bladder from tearing during inflation.



Inventors:
BAXTER ROBERT O
Application Number:
05/424796
Publication Date:
02/25/1975
Filing Date:
12/14/1973
Assignee:
INTERNATIONAL PAPER COMPANY
Primary Class:
Other Classes:
206/522
International Classes:
B60P7/06; B61D45/00; B65D81/05; (IPC1-7): B60P7/14
Field of Search:
9/316 152
View Patent Images:
US Patent References:
3442402DUNNAGE SERVICE1969-05-06Baxter
3414140Dunnage1968-12-03Feldkamp
2993217Life preserving devices1961-07-25Switlik



Primary Examiner:
Werner, Frank E.
Attorney, Agent or Firm:
Michaelsen, Alfred L.
Parent Case Data:


This is a continuation of application Ser. No. 264,410, filed June 20, 1972
Claims:
I claim

1. In a dunnage bag having a substantially air tight bladder encased within a plurality of reinforcing sheets and including a valve mounted through said plurality of reinforcing sheets and providing fluid communication to the interior of said bladder, the improvement which comprises two unconnected flexible sheets of material interposed between the walls of said bladder, one of said flexible sheets of material

2. The dunnage bag of claim 1 wherein said bladder is a thermoplastic material.

3. The dunnage bag of claim 2 wherein said plurality of reinforcing sheets are paper.

4. The dunnage bag of claim 3 wherein there are at least six paper reinforcing sheets.

5. The dunnage bag of claim 2 wherein said flexible sheets of material are paper.

6. The dunnage bag of claim 5 wherein said plurality of reinforcing sheets are paper.

7. The dunnage bag of claim 6 wherein said flexible sheets of paper are coated with a thermoplastic material on at least one side and are heat sealed to said thermoplastic bladder.

8. The dunnage bag of claim 7 wherein there are at least six paper reinforcing sheets.

9. In a dunnage bag having a substantially air tight bladder encased within a plurality of reinforcing sheets and including a valve mounted through said plurality of reinforcing sheets and providing fluid communication to the interior of said bladder, the improvement which comprises a sheet of flexible material interposed between the walls of said bladder and folded to form two overlapping sheets, one of said overlapping sheets:

10. The dunnage bag of claim 9 wherein said bladder is a thermoplastic material.

11. The dunnage bag of claim 10 wherein said sheet of flexible material is paper.

12. The dunnage bag of claim 11 wherein said plurality of reinforcing sheets are paper.

13. In a dunnage bag having a substantially air tight bladder encased within at least one reinforcing sheet and including an inflating valve operatively mounted in one wall of said bag, the improvement which comprises a sheet of flexible material disposed within said bladder between said valve and the wall of said bladder opposite thereto, said sheet of flexible material being secured to said bladder so as to flutter while said bag is being inflated through said valve whereby the fluttering of said sheet of flexible material dissipates the energy of the inflating air stream and thereby protects said bladder from the destructive force of an inflating air stream.

Description:
BACKGROUND OF THE INVENTION

Field to Which the Invention Applies

In the transportation of various articles and commodities, e.g., rolls of paper, the articles are placed in a vehicle such as a railroad car. After the articles are placed therein, it is desired to provide means to insure that the articles do not move during transport. Thus, carriers resort to the use of so called dunnage bags. Such bags are placed between the articles to be transported and are inflated so as to provide a resilient cushion between the articles and between the articles and the walls of the vehicle. During transport, movement of the articles is restrained and the articles are protected from damage. When the articles reach their destination, the dunnage bags are deflated and removed so as to facilitate unloading of the articles.

Because of high transportation costs, an emphasis has recently been placed upon disposable dunnage bags which may be deflated and discarded when the articles reach their destination. Since dunnage bags of this type, i.e., disposable dunnage bags, are used only once, the art has endeavored to so construct these bags as to minimize the cost thereof. A general result of this effort has been the evolution of a dunnage bag wherein the bladder or air containing part of the bag is constructed of a relatively thin walled thermoplastic material, such as polyethylene or other polyolefins, surrounded by or encased in a plurality of webs or sheets of paper. With a dunnage bag construction of this type, the bladder serves mainly as an air tight member while the plurality of paper sheets provide the requisite strength.

As a consequence of constructing dunnage bags as described above, i.e., using a thin walled plastic liner, the bladder possesses relatively little strength. Although this weakness of the bladder is relatively unimportant when the bag is fully inflated because the strength is then provided by the reinforcing sheets, a problem is created and frequently encountered during the inflation of such a dunnage bag at which time the bladder will often fail.

More specifically, the user of a dunnage bag desires to inflate the bag as rapidly as possible. In the typical dunnage bag construction, a valve is mounted through the reinforcing sheets and heat sealed to the thermoplastic bladder so as to provide an air or fluid communication between the interior of the bladder and the exterior of the bag. When the bag is to be inflated, a pressurized source of air, e.g., the holding tank of an air compressor, is connected to the valve and air is discharged into the bladder. At this time, the bladder is rather limply disposed within the reinforcing webs and is free to flutter. Thus, when the high pressure air is discharged into the bladder, vortices generated by the discharge air within the bladder can cause the bladder to vibrate at high frequencies and sufficiently high amplitudes that the bladder will, on occasion, fail, for example the bladder will tear. Additionally, because the cross sectional area of the valve is quite small, the inflating air is discharged into the bladder at a relatively high velocity and will possess substantial kinetic energy. In the usual dunnage bag construction, the valve is disposed in one of the walls of the bag. Thus, the high velocity, high energy air stream will impinge directly upon the opposite, interior wall of the bladder. Under many circumstances, the inflating air stream will be at a sufficiently high velocity and possess sufficient kinetic energy that it will perforate the bladder.

The invention disclosed herein pertains to a method and construction whereby the failure of the bladder of a dunnage bag during inflation is avoided.

PRIOR ART

The prior art has, generally, directed its attention to providing dunnage bags having specific constructions which either increase the strength of the bag or decrease the cost thereof. Thus, different dunnage bag constructions are disclosed in U.S. Pat. Nos. 2,075,166, 3,072,270, 3,199,689, and 3,243,822.

The only prior art of which I am aware and which specifically relates to providing a dunnage bag especially adapted to withstand forces imposed by the inflation thereof is U.S. Pat. No. 3,414,140 to Feldkamp. In the Feldkamp patent, a dunnage bag is disclosed wherein a reinforcement patch is provided on the bladder wall opposite the valve inlet to the bladder. This reinforcement patch is completely secured or adhered to the bladder wall opposite the valve and functions as a stiffener to stiffen the bladder in the region of the patch so as to minimize weakening of the bladder in that region due to forces on the bladder caused by the in-rushing air when the bag is inflated. As such, it will be appreciated that the construction taught by Feldkamp statically absorbs the kinetic energy of the in-rushing air, i.e., the patch does not move separate from the bladder wall and merely acts as a shield. Additionally, it has been found through experimentation that the use of such a reinforcement patch can act as something of a heat shield. That is to say, it has been have observed that during the inflation of a dunnage bag, that portion of the bladder wall opposite the air inlet often displays a surface appearance, subsequent to inflation, which indicates that a burning action has taken place. Indeed, through the use of high pressure air, it is often found that a hole is literally burned through the bladder in the region opposite the valve inlet. Presumably, this burning action or zone of increased temperature arises when the high velocity air flow is impinged upon the bladder wall thus causing the air flow to stagnate. It is believed that this stagnation, according to fundamental fluid dynamic theory, elevates the temperature of both the air and the bladder through a conversion of the kinetic energy of the air stream into heat. In any event, it may be objectively observed that a hole may be produced in the bladder wall and the surrounding area evidences a burning action. Thus, by providing the reinforcement patch of Feldkamp, the reinforcement patch rather than the bladder wall absorbs the kinetic energy of the stream. Thus, it has often been observed that the reinforcement patch of Feldkamp may be deformed or burned as a result of the inflating step.

Considering the manner in which the reinforcement patch of Feldkamp functions as described above, it will be appreciated that Feldkamp's reinforcing patch statically absorbs the kinetic energy of the air stream.

In the course of conducting experiments on dunnage bags having a reinforcement patch of the type disclosed by Feldkamp it has been observed that notwithstanding the presence of the patch, the inlet pressure of the air stream must be limited, e.g., to less than 50 psi. If higher upstream inlet pressures are used, the reinforcement patch will generally fail often resulting in damage to the bladder. Additionally, it has been observed that irrespective of the inlet pressure, damage to the bladder wall which contains the inlet valve often results. Presumably, this results from air impinging upon the bladder after being redirected by the bladder wall opposite the inlet valve. Clearly, the construction disclosed by Feldkamp is of no effect with respect to protecting the bladder wall which contains the air valve. Additionally, the construction disclosed by Feldkamp is believed to be ineffective to prevent damage to the bladder as a result of vibration of the bladder as heretofore described.

In summary, the construction disclosed by Feldkamp provides a limited solution to the problem of protecting the bladder wall of a dunnage bag during inflation. The protection provided by the Feldkamp construction is limited because the bladder wall which contains the air inlet valve is not protected and, additionally, unless the upstream pressure of the inflating air supply is limited, the reinforcement patch and the bladder wall behind the reinforcement patch may be damaged and fail or the bladder may fail because of vibrational stresses.

SUMMARY OF THE INVENTION

Two sheets of flexible material are interposed between the walls of the bladder of a dunnage bag. One of the sheets of flexible material is secured to the wall of the bladder at the area surrounding the valve inlet. The second sheet of flexible material is secured to the wall of the bladder opposite the valve inlet. Alternatively, the second sheet of flexible material can be a continuation of the first sheet of flexible material.

During the process of inflating the dunnage bag, the sheets of flexible material flutter or vibrate as the inflating air fills the bladder. The fluttering or vibration of the flexible sheets of material dynamically absorbs the kinetic energy of the inflating air stream. Simultaneously, the sheets of flexible material protect the walls of the bladder from direct impingement by the inflating air stream.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary, perspective view, partly in section, of a dunnage bag of the type in which the instant invention may be employed.

FIG. 2 is a sectional view of the dunnage bag of FIG. 1.

FIG. 3 is a section view of a dunnage bag employing the instant invention.

FIG. 4 is a plan view of a flexible sheet of material used in the practice of the instant invention.

FIG. 5 is a view, in section, of the bladder of a dunnage bag.

FIG. 6 is a fragmentary view, in section, of a dunnage bag and showing another embodiment of the instant invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings and particularly FIGS. 1 and 2, there is shown an exemplary dunnage bag of the disposable type. Although the particularly construction utilized for a dunnage bag is generally not of significance with respect to the utilization of my invention, the dunnage bag shown in FIGS. 1 and 2 is illustrative of the construction used in the prior art. In this construction, six plies of paper 12, 14, 16, 18, 20 and 22 are wrapped about a longitudinal axis to form longitudinal overlapped joints 17 which are generally adhesively secured. As such, there is provided six tubes. In order to provide the required strength yet maintain minimum cost, the tubes are generally constructed of paper.

While there are a number of constructions available for sealing the ends of the tubes, one commonly employed construction is that which is shown in FIGS. 1 and 2 wherein each of the plies of material which comprises one wall of the tube is provided with a continuous extension flap 12a-22a, which may be folded over on top of the respective plies of the other wall and adhesively secured thereto as shown in FIG. 2 at 15.

Disposed within the reinforcing sheets 12, 14, 16, 18, 20 and 22 is an air tight bladder 29. The bladder 29 is generally a thin walled tube of polyethylene which has been extruded as a tube. At the longitudinal ends, transverse seals may be conveniently obtained by transversely folding the bladder as at 9 and heat sealing the transverse fold. Added strength may be obtained by insuring that the flap 12a on the inner most reinforcing sheet 12 encompasses the transverse fold 9 of the air tight bladder 29. Disposed through the reinforcing walls is a valve 10 through which the bladder may be filled.

Having established the construction of a representative, disposable dunnage bag, there is shown in FIG. 3 a dunnage bag 30 of a construction similar to that which is shown in FIGS. 1 and 2 except that the dunnage bag of FIG. 3 is shown as having been adapted to practice the instant invention. For purposes of clarity, the dunnage bag of FIG. 3 employs only two reinforcing sheets 31 and 32 as opposed to the six reinforcing sheets shown in FIGS. 1 and 2. Within the dunnage bag 30 there is provided a bladder having a front wall 25 and rear wall 27. The bladder is encased within the reinforcing sheets 31 and 32. Mounted through the reinforcing sheets 31 and 32 is a valve 10 which provides fluid communication with the interior of the bladder. More specifically, a grommet 19 having opposing faces 13 and 21 is mounted through the reinforcing sheets 31 and 32. The opposing faces 13 and 21 of the grommet 19 are crimped to grip the reinforcing sheets 31 and 32. Disposed through the interior of the grommet 19 is valve 10 with a flange 23 at one end thereof. The flange 23 and the exterior of the valve 10 may be advantageously constructed of polyethylene. A retaining ring 15 is disposed about the exterior of the valve 10, as shown in FIG. 3. Although not shown in FIG. 3, the valve 10 may be provided with an annular groove which engages the interior of the retaining ring 15. In this manner, the retaining ring 15 exerts a force upon the valve 10 which tends to pull the valve 10 away from the bag 30. Thus, the flange 23 of the valve 10 is urged against the interior face 21 of the grommet 19 thereby locking the valve in position. In the preferred embodiment of my invention as shown in FIG. 3, the flange 23 of the valve 10 is adhesively secured to bladder wall 25. If the flange 23 is constructed of polyethylene and if the bladder is polyethylene, such an adhesive securement can be conveniently achieved by heat sealing. In any event, by sealing the flange 23 to the bladder wall 25, fluid communication is provided to the interior of the bladder through the valve 10. Of course, within the interior of the valve 10 there may be disposed mechanical valve means for permitting air to flow into the bladder but restricting air flow from the bladder. Since such mechanical valve means are well known to those skilled in the valve art, the details thereof have been omitted from FIG. 3.

According to my invention, there is interposed between the bladder walls 25 and 27 a sheet of flexible material 32 which has been folded at a fold line 35 to form two overlapping sheets 33 and 34. The sheet of flexible material 32 is shown in a flat, unfolded condition in FIG. 4. Referring to FIG. 3 and FIG. 4, it will be observed that the first overlapping sheet 33 is provided with an aperture 36 that is coaxially aligned (FIG. 3) with the inlet from the valve 10. The overlapped sheet 33 may be adhesively secured to the bladder wall 25 in the area surrounding the valve 10. That is to say, an adhesive may be deposited on the interior of the bladder wall 25 opposite the valve flange 23 and the overlapped sheet 33 may thus be secured to the bladder wall 25. It has been found that a desirable construction for facilitating this adhesive securement resides in providing a polyethylene coating on the surface of the overlapped sheet 33 which faces the bladder wall 25. In this manner, a separate adhesive does not have to be supplied since the face of the overlapped sheet 33 may be heat sealed to the bladder wall 25 peripherally of the valve 10.

Considering the preferred embodiment of my invention as shown in FIG. 3, it will be appreciated that when the dunnage bag of FIG. 3 is inflated, the bladder walls 25 and 27 will be protected from a direct impingement of the inflating air stream by the overlapped sheets 33 and 34. While this attribute of my invention is significant, it has been surprisingly and unexpectedly observed that the two sheets 33 and 34 may be constructed of a particularly light-weight material. Indeed, it has surprisingly been found that the flexibility of the sheets 33 and 34 contributes most significantly to the protection of the bladder walls 25 and 27. While the mechanism by which this protection is attained is not fully understood, it is believed that the flexible sheets 33 and 34 protect the bladder walls 25 and 27 by dynamically absorbing the kinetic energy of the inflating air stream, i.e., by vibrating and fluttering during the process of inflating the bag. Thus, during experiments conducted on the occasion of this invention, it was observed that if the sheets 33 and 34 are flexible, they flutter and vibrate quite vigorously during the inflation of the bag and particularly during the initial stages of the inflation of the bag which is the time during which a failure of the bladder wall is most often encountered. Indeed, it has frequently been observed that the flutter and vibration of the flexible sheets 33 and 34 often occurs to such a degree that the sheets are completely shredded. Based upon these observations, it has been postulated that the energy which causes the flexible sheets 33 and 34 to flutter and vibrate is derived from the kinetic energy of the inflating air stream. Thus, the energy of the air stream is dissipated by the flexible sheets of material and is not available for damaging the bladder. Similarly, it is believed that a concomitant protective effect resides in the continuous redirection of the inflating stream. In other words, because the flexible sheets of material are fluttering and vibrating, the inflating air stream impinges upon the sheets at a continuously varying angle, causing the air stream to be continuously redirected. Clearly, these mechanisms for protecting the bladder walls 25 and 27 are manifestly different from the prior art approach wherein protection of only a part of one of the bladder walls was sought through the expedient of providing a stiff reinforcement shield and thus statically absorbing the kinetic energy of the inflating air stream.

The method and construction heretofore described with reference to FIG. 3 is particularly effective for protecting the bladder walls under certain circumstances which are commonly encountered. For example, just prior to the inflation of a dunnage bag of the type shown in FIG. 3, it often occurs that the bladder wall 27 is in close proximity to the bladder wall 25, e.g., they are approximately an inch apart. When this condition occurs and assuming that two flexible sheets 33, 34 are not employed, a surprising phenomenon may be observed when high pressure air is initially discharged into the bladder. Under such conditions, the bladder wall 27 will not, as expected, move away from the valve inlet. Rather, the bladder wall 27 remains stationary or, on occasion, may even move closer to the air inlet from the valve 10. It is believed that this phenomenon results from the redirecting of the high velocity air entering the bladder. That is to say, as the high velocity air enters the bladder and impinges upon the bladder wall 27, it is redirected as shown by the arrows in FIG. 5. Thus, a high velocity air stream flows past the bladder 27 opposite the valve 10 and, presumably, a Bernoulli effect occurs creating a low pressure in this area. Thus, the bladder wall 27 may remain stationary or even move closer to the inlet from the valve 10. In either event, the bladder wall 27 is thus subjected to all the deleterious effects of the high velocity, high energy air stream and often fails. Recognizing this phenomenon, it will be apparent that the prior art technique of utilizing a reinforcement patch on the bladder 27 opposite from the air inlet from the valve 10 provides no means for preventing this undesirable effect. However, in contradistinction, it will be appreciated that a utilization of the instant invention obviates this effect with respect to the bladder wall 27. That is to say, by employing the instant invention wherein a flexible sheet is disposed opposite to the inlet of the valve 10 (FIG. 3), the flexible sheet 34 may remain stationary or be drawn into the inflating air stream but the bladder wall 27 will be uneffected by the fluid dynamic effects and will be free to move away from the valve inlet.

Another embodiment of my invention is presented in FIG. 6 wherein the construction of the dunnage bag per se is substantially the same as the construction presented in FIG. 3. However, it will be observed that the two flexible sheets of material 41, 42 interposed between the bladder walls 25 and 27 are separate from each other as opposed to being joined at a fold line as in the embodiment of FIG. 3. Thus, in the embodiment of FIG. 6, the flexible sheet of material 42 is secured to the bladder wall 27 at 43. The sheet of flexible material 41 is secured to the bladder wall 25 in the same manner as heretofore described with respect to the embodiment of FIG. 3. As heretofore indicated, the securement of the flexible sheets of material to the bladder walls may conveniently be achieved by the employment of an adhesive. Similar to the embodiment of FIG. 3, a most convenient adhesive securement means resides in providing a polyethylene or other thermoplastic coating on the surface of the sheets 41, 42 which face the bladder walls. In this manner, the sheets of flexible material 41, 42 may be heat sealed to the bladder walls. Functionally, the embodiment of my invention as shown in FIG. 6 operates in the manner heretofore described and possesses the advantages of the construction disclosed in FIG. 3.

The flexible sheets of material are preferably paper although flexible sheets of other materials have been found to be satisfactory e.g., flexible sheets of plastic. With particular regard to paper, experiments conducted upon the occasion of this invention have indicated that a paper having a basis weight as low as 40 pounds (40 lbs. per 3,000 square feet), provides the protection and dynamic absorption which is sought.

As previously indicated, a particularly desirable combination with regard to the reinforcing sheets can be achieved if, at least, six reinforcing sheets are employed. Preferably, the reinforcing sheets are paper.

While there has hereinbefore been set forth a number of embodiments of the instant invention, it will be appreciated that these embodiments are merely exemplarily of the instant invention, the true scope of which is defined by the claims appended hereto.