US2851075A - Collapsible tank - Google Patents

Description

Sept. 9, 1958 A. J. PALFEY COLLAPSIBLE TANK 2 Sheets-Sheet 1 Filed April 2, 1956 I, I 41 40a m m m E V a N m R 0 r r T e n w fl Y B Q Sept. 1958 A. J. PALFEY 2,851,075

7 COLLAPSIBLE TANK Filed April 2, 1956 1 2 Sheets-Sheet 2 INVENTOR.

HTTORNE vs United States atent CQLLAPSKBLE TANK Albert J Palfey, Midland, Mich, assignor to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Application April 2, 1956, Serial No. 575,474

Claims. (Cl. Nil-4L5) This invention relates to collapsible tanks and particularly to collapsible tanks which are adapted for use on sloping terrain.

Flexible, collapsible fabric vessels or tanks for the storage of fluids range in size from those having a capacity of a few hundred gallons to those having a capacity of many thousands of gallons. The use of such tanks is becoming more common because of their light weight, small storage space requirements when not in use, case of transportation of the tanks to locations where needed, and ease of handling of the tanks. Flexible tanks are well adapted to use in oil and water well treatments, for example, in which large volumes of fluids are used and provision for at least temporary storage at the well site must be provided. Other uses, such as for, temporary fuel storage for either military or civilian purposes, have been suggested.

In the treatment of oil and water wells, the treating equipment is moved from job to job as much as 6 or 8 times a day. Hence, the time and special equipment needed to prepare leveled sites for collapsible tanks usually proves too costly. Because of the tendency of collapsible tanks to roll when disposed on sloping surfaces, it has heretofore usually been necessary to hold the tanks in position with guy ropes or by blocking or bracing the tank. Such expedients are time consuming and sometimes impossible to use.

While it is true that collapsible tanks can be constructed which are stable even when filled on sloping terrain, the shape of such tanks is such that a large wall surface area is required in relation to the fluid capacity of the tank and consequently the tank in its empty condition is bulky and difficult to load and unload from the vehicle in which it is transported from location to location.

Thus, in order that the bulk of the tank be small in relation to its capacity, a generally cylindrically shaped tank (with hemispherical end sections) is highly desirable despite the rolling tendencies of tanks of that shape. Also, sausage shaped tanks, when collapsed, may easily be folded or rolled into a compact bundle.

Accordingly, a principal object of this invention is to provide an improved, compact collapsible tank which is stable when the tank is disposed on a slope.

Another object of this invention is to provide an improved, more compact collapsible liquid storage tank which does not require external holding means to prevent excessive rolling of the tank on sloping terrain.

In accordance with this invention there is provided a. collapsible tank having a generally cylindrical transverse central section (but elliptically shaped in transverse cross sectional configuration when the tank is filled and lying on level terrain) and having generally hemispherically shaped end sections. The tank has a plurality of flexible straps disposed symmetrically with respect to a vertical central plane extending from end to end through the tank. The straps or stabilizer elements may be arranged in either one or two rows on each side of the central vertical plane,

depending on the degree of stability required and the 2 shape of the tank When filled. The length of the straps and their points of attachment to the tank must be within suitable positioning limitations to achieve effective stabilizing action against rolling.

The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which:

Fig. 1 is a top view, partly broken away to show internal constructional features, of a filled .collapsible tank in accordance with this invention;

Fig. 2 is a side elevational view of the tank shown in Fig. 1;

Fig. 3 is a transverse enlarged sectional view, taken along the line 3-3 of Fig. 1;

Fig. 4 is a sectional view taken along the line 44 of Fig. 3;

Fig. 5 is a transverse section through a tank similar to that of Fig. 1 and having two sets of internal stabilizers, two of the stabilizers being anchored to the bottom of the tank along the vertical center line of the tank;

Fig. 6 is a similar section to Fig. 11, but with the tank shown disposed on a sloping surface;

Fig. 7 is similar to Fig. 6, but shows a tank containing only a single set of stabilizer elements;

Fig. 8 is a sectional view taken along the line 88 of Fig. 5;

Fig. 9 is a fragmentary sectional view, similar to Fig. 4, but showing an alternative stabilizer arrangement .comprising a network of rope-like elements;

Fig. 10 is a transverse sectional view of a collapsed tank having one set of stabilizers;

Fig. 11 is a transverse sectional view of a collapsed tank having two sets of stabilizers, and

Fig. 12 is a fragmentary sectional view, similar to Fig. 4, but showing the tie points for the stabilizers aligned with respect to one another whereby the stabilizers are disposed perpendicularly with respect to the longitudinal exis of the tank.

Referring to the drawings and particularly to Figs. 1-4 inclusive, there is shown a collapsible tank, indicated generally by the numeral 30, shown inflated and disposed on a level surface 32. The tank 30 is elongated, of roughly elliptical transverse cross sectional configuration and has dished shaped or somewhat hemispherically shaped end sections.

The tank 30 is, as illustrated, a two ply multiple section construction, the seams 31, 33 between sections of each ply being staggered.

The wall 34 of the tank 30 is composed of fluid-tight sheet material, for example rubberized fabric. The tank has a plurality of hand hold and handling straps 36 aflixed thereto along the sides of the tank 30 and at the ends.

Vents 38 are provided at or near to the top of the tank 30. The vents 38 may be shut ofi if, for example, it is desired to preclude entrance of air.

A tube 40 which serves as a fluid inlet and outlet extends through one end of the tank 42. The part 40a of the tube 40 which lies within the tank 30 has a plurality of apertures 41 to facilitate the discharge of fluid from the tank Fall. The tube 40 is fed through the tank end 43 in any desired fluid-tight manner. The end of the tube 40 which lies outside of the tank 30 conveniently terminates in a quick detachable type coupling unit 42. The inlet-outlet tube 40 is illustrated as entering at the center of the end 42 of the tank 30. However the tube 41 may be at one side of the tank 30 or otherwise disposed to project along the bottom inside the tank.

Referring particularly to Figs. 3 and 4, it may be seen that the tank 30 contains internal bracing or stabilizing tie members, for example, straps indicated generally by the numeral 44, which are symmetrically disposed on each side of the vertical longitudinal plane 46 of the longitudinal axis of the tank 30. As shown in Fig. 4, the internal tension members or stabilizer elements braces 44, in the form of flexible cables or straps, are generally equally spaced one from anotherv at their points of attachment along the length of the tank. A spacing between the points of attachment of the stabilizer elements 44 to the tank 30 of about the girth dimension of tank 30 has proven to be a good spacing, although other spacings may be used.

Except at the ends of the tank, the stabilizer elements 44 are preferably attached in twos at each of the tie points 48 and 52. The upper tie points 52 are in transverse vertical planes which are longitudinally offset from those of the lower tie points 48. Thus, the stabilizer elements 44 do not extend directly outward from their points of attachment 48 to the points of attachment 52 on the sides of the tank 30, but approach the tie points 52 obliquely as shown more particularly in Fig. 1. This arrangement of the stabilizer elements 44 results in a tank 30 which is stable in all directions against rolling when filled and on a sloping surface or support. Therefore the tank does not have to be as carefully oriented on the sloping location where it is to be filled as would be necessary if the stabilizer elements 44 were disposed in vertical transverse planes perpendicular to the vertical plane 46.

Fig. 7 shows the cross-sectional appearance of a tank of the type shown in Fig. 1 when disposed on sloping terrain. Although the tank tends to roll counterclockwise, the left hand stabilizer elements 44 restrict the rolling movement of the tank to the distance required to tighten the stabilizer elements on the down hill side of the tank.

Although a tank 30 having left hand and right hand stabilizer elements is illustrated, both left hand and right hand stabilizers are not used at the same time to achieve stabilization. Thus, a tank having stabilizer elements on one side only would be practical provided the tank is oriented so that the stabilizer containing side 1 is always the down hill side.

Fig. 10 shows a transverse sectional view of a collapsed tank 30 containing a single set of stabilizer elements 44. The stabilizer elements 44 fold readily leaving a flat pack which may be easily folded for storage and ship ment when the tank 30 is not in use.

Figs. 5 and 6 are transverse cross sections of a tank 30a having two sets of internal stabilizers or braces 44a, 44b respectively, with the tank shown disposed in a level position in Fig. 5 and tilted in Fig. 6. A set of stabilizer elements or braces, as the term is used herein, means stabilizers or braces 44 in corresponding positions on each side of the vertical central plane 46 passing longitudinally through the tank 30 when the tank is disposed on a level surface. Under such conditions the braces 44a constitute one ,set and the braces 44b constitute another set. The lower ends of the braces 44a are attached to the bottom 50a of the tank 30a at the position where the bottom 50a of the tank is intersected by the vertical central plane 46. The braces 44a correspond roughly to the single set of braces shown in 4. The disposition in the tank 30a of each set of braces or stabilizers 44a and 44b will be explained in detail later.

Referring to Fig. 8, as well asto Figs. 5 and 6, the manner of disposing the braces or stabilizer elements 44a, 44b may be clearly-seen. The tie points or points of attachment 54 and 56 on the bottom 50 of the tank 30a are staggered with respect to the corresponding side wall tie points 58 and 60. The tie points 54, 58 are joined together by stabilizer elements 44a and the tie points 56, 60 are joined together by the stabilizer elements 441).

Fig. 11, similar to Fig. 10, shows a collapsed (nu-filled) tank 30a having two sets of stabilizer elements 44a, 44b.

Fig. 9 is a fragmentary sectional view of thegeneral 4 type shown in Fig. 4, but with the stabilizer elements being the individual strands 440 of a net-like structure, indicated generally by the numeral 62. The net-like structure 62 extends between the bottom 50 and side wall 34 to replace the individual stabilizer elements 44 shown in Fig. 3, for example.

Although two of the stabilizer elements 44, 44a, or 44b have been illustrated in the various figures of the drawings as being connected to each of the tie points (except for the end tie point or points, that is), such an arrangement is not essential to achieve stability of the tank 30 or 30a. However, when the points of attachment of the stabilizer elements are staggered with respect to one another, attaching each end of each stabilizer element to a separate tie point would not only add considerably to the cost of fabrication of the tank 30 or 30a, but would result in considerable additional strain being placed on the tank wall between two adjacent tie points.

The length of the stabilizer elements 44, for example, and the positioning of their points of attachment with respect to a vertical central axis 46 determines the degree of stability of a tank 30 containing stabilizer elements.

The weight of the tank fabric with respect to the weight of the liquid load the tank can hold must be considered in determining the point of attachment of the stabilizer elements. For example, in a tank 30 containing a single set of stabilizer elements 44 (as in Fig. 3), and having a fabric to load weight ratio of 1:80 with the tank filled with a liquid having a specific gravity of about 1.0, the array stabilizer elements 44 should be attached to the bottom 50 of the tank 30 at a distance equal to about .114 of the girth dimension of the tank from the vertical center line 46. Similarly, the upper point of attachment or tie point 52 should be about .23 of the girth dimension of the tank from the vertical center line 46. The girth dimension, as used here, is intended as the girth of the tank as measured around the tank at the point of attachment. It should be emphasized that while the dimensional data as to length of stabilizers .44 and the positioning of the points of attachment 48, 52 are such that good tank stability is achieved, points of attachment within the scope of the invention will provide varying degrees of stability. For example, the points of attachment of each array need not necessarily be in a straight line along the tank, but may vary slightly withoutseriously affecting the stability of the tank thus constructed.

The length of each stabilizer element 44 used in tanks having the above mentioned fabric weight to load weight ratio should be about .115 of the girth dimension divided by the cosine of the angle the attached stabilizer element makes (when the tank is inflated by its load on level terrain) with the vertical plane perpendicular to the plane 46 and passing through the point of attachment 48 on the bottom of the tank 30.

To show the effect of a change in fabric weight to load weight ratio on the placement and length of the stabilizer elements, a tank 30 having a fabric weight to load weight ratio of 1:50 should have the upper or side wall tie point located about .22 of the girth dimension from the intersection of the vertical central or axial plane 46 with the top of the tank 30. The bottom tie points 48 should be about .075 of the distance from the intersection of the central plane 46 with the bottom 50 of the tank. The length of each stabilizer element should be about .145 of the girth dimension divided by the cosine of the angle the stabilizer makes (under the conditions described above) with the vertical plane which passes through the point of attachment 48 and is perpendicular to the plane 46.

It may be noted that a fabric weight to load weight ratio becomes smaller, the bottom point goes further from the central vertical plane 46.

Tanks of the type shown in Figs. 1-3 and made in accordance with the above dimensional data have proven senses to be stable when filled and emptied on a 20 percent grade. It is also obvious that not all the stabilizers need be attached at tie points 48 or 52 which are the same distance from the intersection of the plane 46 with the top or bottom of the tank. The data given for the length and points of attachment of the stabilizers is by Way of example of generally good design and not intended to completely define the scope of the invention. Further although tanks having fabric weight to load weight ratios greater than 1 to 50 or 1 to 80 may occur, the range between the two specifically given ratios are to be preferred generally.

The dimensional data for tanks 30a having two sets or arrays of stabilizer elements 44a, 44b, as in Fig. 5, are given with respect to the distances A, B, C, D, and E indicated in Fig. 5.

The dimension B should be equal to .095 of the girth dimension (as previously defined). The dimension B should be between .05 and .12 of the girth dimension, as defined above, the longer lengths (towards .12) being from tanks 30 having fabric weight to load weight ratios smaller than 1:50 (as 1:80, for example). In tanks in which the stabilizer elements lie in a vertical plane perpendicular plane 46, the combined dimensions B plus C times the cosine of the angle the stabilizer element C makes with the vertical plane passing through the bottom point of attachment of the stabilizer and perpendicular to the plane 46 should not exceed .25 of the girth of the tank 30a and should be equal to or slightly less than dimension A. Thus, dimension A should not exceed .25 of the girth dimension of the tank. The dimensions C or D should be between .9 and 1.0 times the linear distance between the proposed points of attachment.

The above data is given for stabilizing a tank for use on a 20 percent grade. As stated in connection with tanks 30 having but a single set of stabilizers 44, alternative stabilizer dimensional and placement arrangements may provide suitable stabilization of the tank for other tank usage requirements.

In operation, whether one or two sets or arrays of stabilizers are used in the tank, the bottom of the tank is held down by the weight of fluid in the tank and thus serves as an anchor for the stabilizers. But the fabric weight also contributes to the effectiveness of the bottom of the tank as an anchor for the stabilizers as previously mentioned.

Reference is now made to the operation of collapsible tanks. On a sloping supporting surface, that is, sloping terrain a flexible fabric vessel containing a liquid will roll and coast down hill due to the resultant horizontal component of the vertical fluid pressure tank.

Since the unbalanced forces phenomenon discussed above presents stationary and moving sections, advantage is taken of this fact to hold the tank stationary by joining together the bottom or normally stationary sections with those sections which potentially tend to move, or the top and side sections, with arrays of stabilizers or braces 44, 44a, or 4th of negligible stretch.

The length of the various stabilizer elements has been described in terms of the cosine of the included angle made between a stabilizer element and a vertical plane perpendicular to the central or axial vertical plane 46 of the tank. In most tanks the said included angle will not exceed 45 and may even be degrees in which case the cosine of the angle is of course 1. Tanks having stabilizer elements whose above defined included (angle is 0 degrees are disclosed and claimed in applicants copending application Serial No. 556,573, filed December 30, 1955, entitled Collapsible Tank, now abandoned.

Fig. 12, similar to Fig. 4, illustrates a tank in which top and bottom points of attachment (48, 52, for example) of the stabilizer elements lie in the same vertical plane which is perpendicular to the vertical axial plane 46. Thus, as mentioned above, the included angle is zero and the cosine of zero degrees is 1, as described above.

It is assumed in the above discussion that the longitudinal axis of the tank is preferably arranged horizontally when the tank is used on a slope.

It is realized that for other uses, such as military use, for example, tanks which are stable on steeper slopes than 20 percent slopes maybe desired. Such tanks may be constructed in accordance with this invention by providing a suitable B dimension as described for the fluid weight to fabric weight ratio involved.

In the discussion of stabilized tanks made in accordance with this invention, no mention has been made of the coetlicient of friction between the tank and its support (earth, platform, etc.) and its eifect on the stability of the tank 30. It is assumed that the support will be earth which is not unduly pebbly in nature and that the support is not ice covered. Under conditions where the tank is disposed on pebbly or icy terrain, the degree of stability of the tank will necessarily be reduced to the extent that the horizontal component of the frictional force between the surface of the bottom of the tank and its supporting surface is decreased.

This application is a continuation-in-part of my copending application Serial No. 556,573, filed December 30, 1955, entitled Collapsible Tank, now abandoned.

I claim:

1. In a flexible fabric walled elongated tank adapted to hold a liquid, said tank being generally symmetrical about the vertical plane of the longitudinal axis when resting oria level surface, at least one array of flexible stabilizer members inside the tank, each of said members having one end held to the upper side of the tank at a point remote from the vertical plane of the longitudinal axis of the tank and the other end held to the bottom side of the tank nearer to the said vertical plane than the end held to the upper side and having a length less than the shortest peripheral distance measured along the inside surface of the tank between the said holding points, each said member when taut sloping from the upper to the lower end toward the said vertical plane.

2. In a collapsible flexible fabric walled elongated tank wherein an array of flexible stabilizing tension members are disposed on each side of the vertical plane of the longitudinal axis of the tank.

3. A collapsible tank in accordance with claim 2, adapted to hold a liquid, said tank being generally symmetrical about the vertical plane of the longitudinal axis when resting on a level surface, an array of flexible stabilizing tension members inside the tank disposed on at least one side of the vertical plane of the longitudinal I axis of the tank, each member having one end held to the upper side of the tank and the other to the bottom side, the lower end of each tension member being nearer to the said vertical plane than the other end and having a length less than the shortest peripheral distance measured along the inside surface of the tank between the said holding points of the-tension members.

4. A collapsible tank in accordance with claim 2, wherein said tank has a plurality of arrays of said flexible stabilizing members disposed on each side of the vertical plane of the longitudinal axis of the tank.

5. In a collapsible, flexible fabric walled, generally symmetrical elongated tank adapted to hold a liquid and having its top, bottom, and sides symmetrically disposed on each side of the vertical plane of the longitudinal axis of the tank when the tank bottom is disposed on a level supporting surface, the vertical plane passing through the top at a top intersection line and through the bottom at a bottom intersection line, a plurality of flexible stabilizer elements secured to and within the tank wall between top and bottom points of attachment thereto, said top points of attachment of each stabilizer element being disposed at a distance from the said top intersection line of between .09 and 0.25 ofthe girth 'dimension'of the tank as measured through said bottom pointof attachment of each stabilizeri said bottom points of attachment of each stabilizer element being disposed on the same side of said vertical plane of the longitudinal axis as is its top point of attachment and at a distance from the said bottom intersection line of not greater than 0.125 of said girth dimension as measured above,the length of each stabilizer element being between .9 and 1.0 times the linear distance between its points of attachment as measured before said stabilizer element is attached thereto.

6. In a collapsible, flexible fabric walled, generally symmetrical elongated tank adapted to hold a liquid and having its top, bottom, and sides symmetrically disposed on each side of the vertical plane of the longitudinal axis of the tank when the tank bottom is disposed on a level supporting surface, the vertical plane passing through the top at a top intersection line and through the bottom at a bottom intersection line, a plurality of flexible stabilizer elements secured to and within the tank wall between top and bottom points of attachment thereto, said top points of attachment being disposed on the top and bottom point of attachment for each of the individual stabilizer elements being on the same side of the plane of the longitudinal axis of the tank, on opposite sides of and at a distance from thesaid top intersection line of between .2 and 0.25 of the girth dimension of the tank as measured through the individual bottom points of attachment, said bottom points of attachment being disposed on opposite sides of and at a distance from the said bottom intersection line of not greater than 0.125 of said girth dimension, the length of each stabilizer element being not greater than where A is .9 times the distance between the top point of attachment and the top intersection line minus the distance between the bottom point of attachment and said bottom intersection line, and B is the included angle at which each stabilizer element meets the vertical plane passing through the 'bottom point of attachment of each stabilizer element and perpendicular to the vertical plane of the longitudinal axis.

7. In a collapsible, flexible fabric walled, generally symmetrical elongated tank adapted to hold a liquid and having its top, bottom, and sides symmetrically disposed v on each side ofthe vertical plane of the longitudinal axis of the tank when the tank bottom is disposed on a level supporting surface, the vertical plane passing through the top at a top intersection line and through the bottom at a bottom intersection line, a plurality of flexible stabilizer elements secured to and within the tank well between top and bottom points of attachment thereto, said top points of attachment being disposed, on opposite sides of and at a distance from the said top intersection line of 0. 23 of the girth dimension of the tank as measured through the'bottom point of attachment'of each stabilizer element, said bottom points'of attachment being disposed on opposite sides of and at a distance from the said bottom intersection line .of 0.125 of said girth dimension, the length of each stabilizer element being not greater than CosB where A is between .9 and 1.0 times the distance between the top point of attachment and the top intersection line minus the distance between the bottom point of attachment and said bottomintersection line, and B is the included angle at which each stabilizer element meets theverftical plane passing through the bottom point of attachment of each stabilizer element and perpendicular tothe vertical plane of the longitudinal axis.

81' 'A collapsible, tank in accordance with claim 4, whereinsaid stabilizer elements on each side of said vertical plane are axially aligned with each other.

9. In a collapsible, flexible fabric walled, generally symm'ertical elongated tank adapted to hold a liquid and having its top, bottom, and sides symmetrically disposed on each side of the vertical plane of the longitudinal axis of the tank Whenthe tank bottom is disposed on a level supporting surface, the vertical plane passing through the top at a top intersection line and through the bottom at a bottom intersection line, an inner array and an outer array of flexible stabilizer elements secured to and within the tank wall between top and bottom points of attachment thereto, said top points of attachment said outer array being disposed on opposite sides of and at a distance from the said top intersection line of between .2 and 0.25 of the girth dimension of the tank as measured through said top point of attachment, said bottom points of attachment of said outer array being disposed on opposite sides of and at a distance from the said bottom intersection line of not greater than 0.125 of said girth dimensions as measured above, the length of each stabilizer element being between .9 and 1.0 times linear distance between the top point of attachment and the bottom point of attachment as measured before said stabilizer element is connected thereto, said bottom point of attachment of said inner array being generally along said bottom intersection line, the top point of attachment being between said top point of attachment of said outer array and said topintersection line, the length of each stabilizer element of said inner array being between .9 and 1.0 times the linear distance between said points of attachment of said inner array before as measured before said stabilizer elements are connected thereto.

10. A collapsible tank in accordance with claim 9 wherein said top point of attachment of said inner array is disposed about .095 of the girth dimension from the top intersection line.

11. A tank in accordance With claim 9, wherein stabilizer elements of said inner and outer arrays are symmetrically disposed on both sides of said vertical plane.

12. A tank in accordance with claim 9, wherein the corresponding stabilizer elements of each array are in axial alignment with one another and the elements of the inner array are interposed with the elements of the outer array.

13. A tank in accordance with claim 5, wherein said stabilizer elements comprise the strands of a net.

14. A collapsible tank in accordance with claim 5, wherein at least one of said stabilizer elements is disposed at an angle with respect to a vertical plane passing through the bottom point of attachment of said stabilizer element and perpendicular to said vertical plane of the longitudinal axis.

15. A collapsible tank in accordance with claim 5, wherein said angle does not exceed forty-five degrees.

References Cited in the file of this patent UNITED STATES PATENTS 2,612,924 Cunningham Oct. 7, 1952 2,724,418 Krupp Nov. 22, 1955 FOREIGN PATENTS; 561,819 Great Britain June 6, 1944 UNITED STATES PA omen CERTIFICATE OF CORRECTION Patent-N0. 2,851,075 September 9, 1958 Albert JP Palfey It is hereby certified that error appearsb in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6, line 44, beginning with '2., In a collapsible flexible fabric" strike out all to and including "tension members." in line 60, and insert instead the following as claims 2and 3:

2. In a collapsible flexible fabric walled elongated tank adapted to hold a liquid, said tank being generally symmetrical about, the vertical plane of the longitudinal axis when resting on a level surface, an array of flexible stabilizing tension members inside the tank disposed on at least one side of the vertical plane of the longitudinal axis of the tank, each member having one and held to the upper side of the tank and the other to the bottom side, the lower end of each tension member beingnearer to the said vertical plane than the other end and having a length less than the shortest peripheral distance measured along the inside surface of the tank between the said holding points of the tension members.

3a A collapsible tank in accordance with Claim 2, wherein an array of flexible stabilizing tension members are disposed on each side of the vertical plane of the longitudinal axis of the tank.

Signed and sealed this 24th day of February 1959,

(SEAL) Attcst: v v

KARL LINE ROBERT c. WATSON] Attesting Officer Commiuioner of Patents

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