US3494509A - Variable volume reservoir - Google Patents

Description

Feb. 10,1970 MC I E I 3,494,509

VARIABLE VOLUME RESERVOIR Filed Jun'e 15, 1966 4 Sheets-Sheet 1 3 :0 2. 2o l8fi CARBURATOR Q I 26 I 48 3o I 'ICONTROLSI 36 I 39 INVENTOR.

33 JOHN S. MGU/RE TO PUMP T0 TANK BY A TTORNE Y3 J14 Sheets-Sheet 2 v Filed Jun; 13, 1966 INVENTOR. JOHN S. MGU/RE ATTORNEYS -Feb.1 0,.197o V 5, m; 3,494509 I I VARIABLE VQLUMEURESEIIVOIR 4 Sheetls-Sheet-fi Filed J de is, 1966 H a m 1% I m m w m m .1...

m m M we I INVENTOR. JOHN S. MGUIRE nrro/eusvs United States Patent 3,494,509 VARIABLE VOLUME RESERVOIR John S. McGuire, P.O. Box 157, Ozark, Mo. 65721 Filed June 13, 1966, Ser. No. 557,170 Int. Cl. B65d 89/04, 35/28 U.S. Cl. 222107 2 Claims ABSTRACT OF THE DISCLOSURE A collapsible or variable volume reservoir or tank having first and second panels or walls disposed in spaced relation and interconnected by a flexible wall to form an enclosure of variable volume. The flexible wall is formed of a flexible synthetic resin material having controlled randomly orientated molecular structure with said flexible wall being in a bellows like form to permit the space between the panels to vary and change the volume whereby it varies in a corresponding manner to the quantity of fluid within the reservoir. The method of making a variable volume reservoir includes the heating and expanding portions of the hollow member to obtain molecular orientation in the material thereof.

This invention relates to material handling systems and more particularly, to a pressure system for moving flowable material including a collapsible or variable volume reservoir or tank and the method of forming said reservoir.

It is desirable in various situations to move flowable material in a completely closed system wherein the material is free from contamination by moisture, dust and the like and wherein oxidation is inhibited in that air is prevented from contactng the material. This is particularly applicable to fuel supply systems such as in various types of vehicles, for instance, automobiles, trucks and aircraft, where contamination of the fuel adversely affects vehicular performance and further, where fumes from the fuel create hazardous conditions. Although some systems are partial- 1y closed, the depletion of material within the system results in the movement of air into the system, particularly in the material reservoir. Contamination, leakage and exposure to air may also occur at various valves and pumps within the normal prior art systems.

Heretofore, variable volume tanks have been developed in an effort to reduce the formation of flammable gasses in the tank with said tank collapsing in a corresponding manner to the removal of fuel from said tank. These tanks, however, have not become commercially accepted primarily as a result of their inability to withstand the pressures, temperatures and the stresses of repeated flexing which are encountered in the environment where the utilization of such structures is desirable.

The principal objects of this invention are: to alleviate the aforementioned difficulties in the art by providing a new and improved variable volume reservoir, container or tank capable of withstanding the pressures, temperatures and repeated flexing to which a reservoir of this nature would be subjected in a multitude of environments; to provide such a reservoir formed by a new and improved method wherein the molecular structure of the reservoir is formed in a controlled random orientation, or in other Words, is comprised of oriented molecular chains disposed along randomly directed planes providing a structure of considerable strength; to provide such a reservoir having sufficient strength to impart or transfer the pressure required to move the flowable material contained in said reservoir such that additional pumping means or valves within the material movement system are not required, thereby eliminating numerous sources of leakage and contaminations; to provide a new and novel method of forming such a variable volume reservoir wherein the entire structure is strengthened by controlled random molecular orientation which effects molecular alignment without creating the weaknesses of single plane molecular orientation which tends to form cleavage planes in the structures; to provide a new and improved system for the handling or moving of flowable material wherein the storage container transmits pressure to the material for effecting the moving of the material; to provide such a system which may be maintained throughout its operation in a substantially closed condition even though the material in said system is being depleted or utilized; to provide a fuel handling system having a variable volume storage reservoir wherein the volume of the reservoir varies in a corresponding manner to the depletion of fuel within said reservoir; to provide such a fuel system wherein depletion of the fuel decreases the volume of the fuel reservoir such that the employment of such reservoir on a vehicle may utilize the decreased volume to raise the reservoir relative to the road surface, thereby increasing the clearance space; to provide such a fuel system wherein the system is substantially closed preventing the entry 'of air to oxidize and otherwise contaminate the fuel and further, to prevent the formation of flammable fumes attendant such fuels; to provide such a system particularly adapted to the movement of jellied fuels employed in high speed aircraft where the jellied fuels may be moved without the adverse effect of channeling wherein the pressure medium seeks a channel through the fuel and often escapes through the fuel flow passage rather than driving the fuel itself through said passage; to provide such a system and reservoir which may be simply and inexpensively manufactured for utilization in various areas such as automobiles and aircraft to greatly increase the efficiency of moving flowable material and establishing a safe condition for the movement of various hazardous materials.

This invention contemplates a variable volume reservoir comprising a first and second panel means with said panel means being disposed in spaced relation and interconnected by a wall means to form an enclosure. The invention further contemplates the inclusion of flexible means on said wall means to allow the relative movement of said panels inwardly and outwardly of one another, said flexible means being formed of a flexible synthetic resin material, said material having a controlled randomly orientated molecular structure or molecular alignment in a plurality of randomly directed planes capitalizing on the strength obtained from molecular alignment without the disadvantage of creating cleavage planes in the structure.

The invention further contemplates a method of forming said variable volume reservoir comprising the steps of forming a parison having an interior configuration like the exterior configuration of the finished product, defining an interior chamber and an exterior, placing said parison in a mold structure, heating said parison to a temperature slightly below the melting point of the crystalline structure of said parison and expanding the heated parison to the desired shape in a controlled manner by regulating a slight pressure differential between a pressure medium in the interior chamber and a medium about the exterior of said parison.

The invention also contemplates that the variable volume reservoir may be employed in systems for the movement of flowable material wherein the system includes means operatively connected to said reservoir to provide a relative movement between the panels of said reservoir to thereby effect a pressure on the flowable material in said reservoir. The pressure applied to the reservoir itself and transmitted through the reservoir to the flowable material is employed to drive or move the flowable material within the material handling system.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein are set forth by way of illustration and example certain embodiments of this invention.

FIG. 1 is a perspective view of a variable volume reservoir, container or tank having a wall portion comprised of a circumferentially extending bellows structure, said reservoir embodying the features of this invention.

FIG. 2 is a diagrammatic view of a system for moving or handling fiowable material, particularly adapted to a system for supplying combustible fuel to the carburetor of an internal combustion engine showing the variable volume tank as it would be utilized in the fuel system of a vehicle such as an automobile.

FIG. 3 is a side elevational view of a portion of the fuel handling system shown in FIG. 2 illustrating the mounting and actuating means of the variable volume reservoir.

FIG. 4 is a vertical sectional view taken on line 44 of FIG. 2 showing the variable volume tank and its actuating means.

FIG. 5 is a modified form of a collapsible tank and actuating means particularly adapted for utilization in an aircraft and capable of being utilized by the movement of jellied fuels and shown as installed within an aircraft wing structure.

FIG. 6 is a vertical sectional view through a mold structure illustrating the placement of a parison in a mold structure and showing a particular type of mold structure which may be employed to create a variable volume reservoir embodying the features of this invention.

FIG. 7 is a vertical sectional view through the mold structure of FIG. 6 showing the parison in its initial stages of expansion wherein the upper and lower panels of the parison have been spread apart such that the lower panel is moved into contacting relation with the bottom surface of the mold structure.

FIG. 8 is a horizontal sectional view through the mold structure of FIG. 6 illustrating a second phase of expansion of the parison wherein a pair of the side walls of the parison are expended into contacting relation with a pair of correspondingly shaped side walls of the mold structure.

FIG. 9 is a vertical sectional view taken through the mold structure shown in FIG. 6 showing the parison in its final stage of expansion wherein the other pair of side walls of the parison are expanded outwardly into contacting relation with the movable side walls of the mold structure.

Referring to the drawings in more detail:

The reference numeral 1 generally designates a variable volume reservoir or tank having first and second spaced panels 2 and 4 respectively With said panels 2 and 4 being joined together by means of a circumferentially extending side wall 6 to form an enclosure defining an inner chamber 8 for storage of a fiowable material. In the illustrated embodiment, the reservoir 1 is rectangular in plan view having a rectangular upper panel 2, a rectangular lower panel 4 with a plurality of side Walls 6 interconnecting the opposed spaced panels 2 and 4 to form the variable volume reservoir 1.

The circumferentially extending wall portion 6 includes flexible means to allow the relative movement of the panels 2 and 4 inwardly and outwardly of one another thereby varying the volume of reservoir and applying pressure on the fiowable material within the reservoir 1 to drive or move the material through a particular system. In the illustrated embodiment, the flexible means is a portion of the side wall 6 extending circumferentially about the reservoir 1 and comprised of a circumferentially extending bellows structure 10. The bellows structure 10, as illustrated, is coextensive with the side wall 6 and extends completely about the reservoir 1 forming an accordian shaped structure which may be forced inwardly and outwardly to apply pressure on the material within said reservoir. The bellows structure 10 is comprised of a plurality of corrugations or alternate grooves and ridges 12 and 14 respectively extending from the upper panel 2 to the lower panel 4 in an integrally formed structure.

The reservoir structure 1 has been so formed with a flexible plastic material of a crystalline structure that the molecular structure of said material has been controlled in a randomly oriented manner such that weaknesses along a single plane orientation or a cleavage plane in the structure have not been created. Although molecular alignment has been created along random intersecting planes to provide additional strength. The random orientation of the molecular structure avoids the cleavage planes normally attendant structures of this nature and the controlled expansion generally regulates the molecular orientation in critical areas of the reservoir 1 such that a reservoir is constructed having unusual strength characteristics. The reservoir may be formed of various plastic materials of a thermoplastic nature or a material tending to return to its original nature after heating and cooling and having the desired characteristics of strength, flexibility and resiliency at a wide temperature range and further, of such a. nature to be inert to the material contained within the reservoir 1. An example of such a material is an olefin plastic material relatively impervious to gasoline.

Referring to FIG. 2, the reservoir structure 1 is illustrated in a fuel system designated by the reference numeral 16 in such a manner that the pressure is exerted on the collapsible reservoir 1 in order to move panels 2 and 4 toward one another, thereby placing the fuel contained within the reservoir 1 under pressure and forcing said fuel through a conduit or passage 18 to a carburetor 20 associated with an internal combustion engine 22. In this manner, the fuel movement or supply system is free of internal pumps and valves which could cause leakage and contamination of the fuel. The particular fuel system, as illustrated in FIG. 2, is of the type which could be adapted for utilization in various vehicles such as automobiles and trucks wherein a hydraulic system 26 is employed to exert the desired pressure on the reservoir structure 1. The system illustrated in FIG. 2 is exemplary only as it is illustrative of a single embodiment or means for applying pressures to the variable volume reservoir 1 for providing sutficient pressure to move a flowable material contained within the reservoir 1 through a flow passage to a desired location.

In the illustrated emodiment, the hydraulic system 26 includes a hydraulic cylinder 28 operatively connected by a pair of hydraulic lines 30 and 32 to a valve 34 which serves to control the flow of hydraulic fluid through lines 30 and 32 to the cylinder 28 to effect an actuation of the cylinder 28. The valve 34 is operatively connected in a conventional manner by lines 36 and 38 to a tank and pump for effecting the flow of hydraulic fluid through the system 26. The valve 34 may be controlled in various manners, but is illustrated herein as a solenoid valve operatively connected by an electric circuit 40 to a set of controls 42 which may be housed in the vehicle and employed for actuating or deactivating the cylinder 28 to apply or remove pressure from the flowable material within the reservoir 1. The pump in the hydraulic system 26 is operatively connected to the engine 22 and upon actuation of the engine 22, pumps fluid through lines 38 and 32 to the cylinder 28. A check valve is included in line 38 to maintain a line pressure on the piston of the cylinder after the deactivation of the engine 22. In order to fill the reservoir 1, the pressure exerted by the cylinder 28 is relieved by activation of valve 34 to line 32 to line 36 and the tank of system 26.

Referring to FIGS. 2 and 3, the piston or driving rod 44 of the hydraulic cylinder 28 is swingably connected by a. suitable fitting 46 to a cross bar 48, said cross bar 48, in turn, being swingably connected to a pair of actuating linkage sets or systems 50 and 52 disposed on opposed sides of the reservoir structure 1. The linkage systems 50 and 52 are employed for moving the opposed panels 2 and 4 of the reservoir 1 together to exert pressure of the flowable material within the reservoir 1.

Referring to FIGS. 3 and 4, the reservoir 1, as illustrated, has an upper or overlying plate 54 in contacting relation with the upper panel 2 and a lower or underlying plate 56 in contacting relation with the lower panel 4, with the plate 56 being adapted for movement inwardly and outwardly from the plate 54 with said plates 54 and 56 serving as pressure means for exerting pressure on the material within the variable volume reservoir 1. In the illustrated embodiment, the plate 54 and 56 are operatively connected for relative movement by the linkage systems 50 and 52 with each of said systems being comprised of a connecting arm or link 58 swingably mounted at an end portion of the cross bar 48. The arm or link 58 is also swingably mounted to linkage means 60 for drawing the plate 54 and 56 inwardly when a. force is exerted an the linkage means by the actuating arm or linkage 58. The linkage means 60 is comprised of a horizontal member or link 62 which is swingably mounted to the linkage 58 and a pair of parallel links or members 64 and 66 swingably mounted to each of the plates 54 and 56 such that the horizontal displacement of the linkage 62 tends to pull the plates 54 and 56 together to exert a pressure on the flowable material within the reservoir 1.

A swingably mounted diagonal bracing member 68 having opposed end portions 70 and 72 swingably connected to the plates 54 and 56 respectively is utilized on opposed sides of the reservoir interiorly of each of the linkage systems 50 and 52 to maintain the plates in a generally opposed relation and prevent the displacement horizontally of the lower plate 56 upon activation of the linkage systems 50 and 52.

The collapsible reservoir 1 contains a filling tube 80 integral with the upper panel 2 through which fluid or other flowable materials may be placed within the reservoir 1 with a displacement cap 82 serving to seal the tube 80 by threaded engagement therewith to prevent the entry of air through tube 80 and into the system 16. The cap 82, as illustrated, includes a protruding portion 84 extending downwardly within the tubular member 80 to effect a displacement of the fluid or flowable material contained within the reservoir 1 in order to insure complete evacuation of air from the system by allowing the fluid or flowable material itself to force the air outwardly upon engagement of the cap 82.

A gauge mechanism 86 is illustrated within the reservoir 1 to maintain an accurate reading of the fuel or other flowable material remaining within the reservoir 1 by monitoring the position of the lower plate 56 in relation to the upper plate 54. In the illustrated embodiment, the gauge 86 is comprised of a rheostat 88 having an arm 90 for varying line resistance extending outwardly therefrom, said rheostate 88 being operatively mounted to the upper panel 2 of the reservoir 1 and the arm 90 extending downwardly toward the lower panel 4. The arm 90, as illustrated, has a roller 92 rotatably mounted to the lower portion thereof and disposed in rolling contacting relation to the lower panel 4 of the reservoir 1 and designed to move laterally across the lower panel 4 on activation of the hydraulic cylinder 28 moving the lower plate 56 upwardly and forcing the flowable material from the reservoir 1. The rheostat 88 indicates the position or angular disposition of-the arm 90 which may be reflected on a suitable reading means in a conventional manner. The conduit 18 includes a flexible end portion 93 which extends through the upper plate 54 and the upper panel 2 of reservoir 1 to a position at the lower portion of chamber 8 where the portion 93 is secured by a connector 94 to the lower panel 4 of reservoir 1. As the reservoir 1 is collapsed, the flexible end portion 93 folds up within chamber 8 with its intake port 96 maintained at a relative position to the lower panel 4 by the connector 94.

In operation, the reservoir 1 is filled with a fluid or other flowable material to the top of the filling tube and the cap 82 is replaced with the protrusion 84 forcing out a certain amount of liquid or flowable material and any remaining air at the top of the tube 80. The hydraulic cylinder 28 is then activated by means of the controls 42 to maintain a desired predetermined pressure on the fuel in the reservoir 1 as the fuel is being depleted through utilization by the engine 22. The hydraulic cylinder 28 maintains a constant pulling force on the cross bar 48 which, in turn, actuates the linkage systems 50 and 52 in such a manner as to pull the plates 54 and 56 inwardly of one another to exert a pressure on and collapse the reservoir 1 as the fuel therein is depleted. The bellows structure 10 of the side wall 6 of the variable volume reservoir 1 allows the reservoir 1 to collapse as the fuel is removed therefrom.

The hydraulic pressure within the hydraulic system 26 can be maintained by a pump operatively connected to the engine 22 with the check valve 39 retaining the pressure when the pump is stopped and the vehicle is in an inoperative condition. In order to fill the tank or reservoir 1, it is necessary to activate the controls 42 to open the line 30 to the line 38 from the pump in order to drive the piston 44 outwardly of the cylinder 28 to thereby spread the spacing between the plates 54 and 56 to allow the collapsible reservoir 1 to be opened.

Referring to FIG. 5, a modified form of a variable volume reservoir or tank arrangement has been illustrated and is designated by the reference numeral 100. The variable column reservoir arrangement 100 is adapted for utilization in the storage and movement of jellied fuels which are normally employed in high speed aircraft. The variable volume reservoir or tank designated as 102 is formed in an identical manner to that illustrated in FIG. 1 with the filling tube 80 omitted and including a filling port 103 and a discharge port 105. The variable volume reservoir 102 has an upper panel 104 and a lower panel 106 disposed in contacting relation to a pair of pressure means illustrated as plates 108 and 110 with said plates 108 and 110 effecting a pressure on the fuel contained within the reservoir 102.

The panels 104 and 106 are operatively connected by means of a circumferentially extending side wall structure 112 having a flexible means to allow the relative movement of the panels 104 and 106 for compression of the fluid within the reservoir 102. The flexible means, as illustrated, is a circumferentially extending bellows structure 114 which is integrally formed with the upper and lower panels 104 and 106 respectively to form an enclosed chamber 116 for storage of a flowable material such as a jellied fuel.

The lower plate 110 is suitably mounted in a fixed position to a pair of frame members 118 as may be found in aircraft wing structures with the plate 108 movable relative to plate 110 and being actuated by an inflatable means 120 suitably mounted in a frame structure 122 such as an aircraft wing structure in overlying relation to the reservoir 102.

The inflatable means 120 is employed in a pressure exchanging manner in order to effect a desired predetermined pressure on the fuel contained within the reservoir 102. As pressure is applied to the inflatable means 120 through suitable means, the plate 108 is forced downwardly towards plate 110, thereby effecting a pressure on the jellied fuel contained within the reservoir 102. As the pressure is being applied evenly across the plate 104, the application of pressure to the jellied fuel is relatively coextensive across the top or upper panel 104 of the reservoir 102. As the pressure medium is not being applied directly to the jellied fuel, but rather through various pressure exchanging means, the effects of channeling whereby the pressure medium itself is lost through the fuel flow line is thereby avoided.

Referring to FIG. 6, a mold structure is illustrated and designated by the numeral 130 which may be employed for forming collapsible reservoirs of the type described herein wherein the molecular structure of the tank itself is formed in a controlled random orientation, thereby avoiding the weaknesses attendant cleavage planes which develop in the expanded enclosed structures of the prior art. The expansion of the preform or parison will tend to create an alignment of the molecular structure of the material along given planes and thereby create cleavage planes. By this method, alignment occurs in a random manner such as intersecting planes of alignment such that cleavage planes are avoided and the structure is strengthened in all directions with specific control" of the molecular alignment.

Initially, a parison or preform 132 is formed by conventional molding processes such as rotational molding with said parison defining an interior chamber 134 and an exterior surface 136 wherein the interior configuration is like that of the exterior of the finished product. The parison is formed of a material such as a thermoplastic synthetic resin which will remain in the condition of the original material after heating and cooling of the material. The parison 132, as illustrated, is molded with a circumferentially extending bellows structure 138 interconnecting an upper panel 140 and a lower panel 142 such that the parison is a miniature unexpanded collapsible tank structure lacking the controlled molecular orientation or alignment of the finished product. The parison 132 includes an entry tube 144 which may later be employed as the filling tube 80 but is utilized during the molding or expanding process as an entry means for a heated pressure medium or fluid.

The mold structure 130, as illustrated, is comprised of an outer box or case 146 having side walls 148, end Walls 150 and upper panel 152 and a lower panel 154. Each of the side walls 148 contains a centrally located portion 156 formed in a corresponding manner to the desired bellows shape of the finished collapsible tank and generally consisting of a plurality of corrugations or alternate ridges and grooves 155 and 157 respectively extending across the height of the side walls 148.

The mold structure 130 also includes a pair of movable end walls 160' slidably retained within the mold structure 130 in spaced relation from the end walls 150 and movable by suitable means 162 operatively connected to the mold structure 130. The movable walls 160 each have an inner surface formed in a corresponding shape to the bellows portion of the finished reservoir 1 and being comprised of a plurality of corrugation or alternate ridges and grooves 161 and 163 respectively to thereby form the bellows structure. Each of the ridges 161 and 155 of the walls 160* and 148 has a cooling tube 164 operatively mounted in relation thereto to effect a heat transfer from the parison as the parison is moved into contacting relation with the walls 160 and 148 to thicken the wall of the parison at the point of contact with the ridges 161 and 155. The tubes 164 are each operatively connected to flexible hoses 166 and 167 which extend outwardly of the mold structure to a suitable heat exchanging means. The walls 160 are each operatively mounted on a pair of arms 168 formed in an L-shaped manner, said arms 168 being received through a pair of slots 170 defined in the side walls 148 and suitably mounted to means for moving the walls inwardly and outwardly from the center portion of the mold structure 130.

The pressure within the mold structure 130 is maintained through a conduit means 172 and gauges 173 which operatively connects said structure 130 to means for providing a pressure medium to the interior of the mold structure 130 through an entry port 174. The movable walls 160 of the mold structure 130 are provided with a plurality of minute apertures which permit the maintenance and control of the desired pressure within the mold structure throughout the entire inner interior of said mold structure 130.

The parison, after being initially formed, is placed within the mold structure with the entry tube 144 extending through an aperture 176 defined in the upper panel 162 with the entry tube 144 being operatively connected to a means for providing a pressure medium to the interior 134 of the parison 132. The pressure medium provided to the interior 134 of the parison 132 throughout the expansion of the parison 132 is heated to a temperature sufficiently high to maintain the temperature of the parison itself at a point slightly below the melting point of the crystalline structure of the material forming said parison 132. A heated pressure medium is also provided through the conduit 172 and ports 174 into the interior of the mold structure to effect even heating of the parison 132, to allow control of the pressure differential between the interior 134 of the parison and the interior 157 of the mold structure in such a manner as to accurately control the expansion of the parison 132 and apply a uniform compressive force on the walls of the parison during its expansion. The employment of the pressure differential during the expansion prevents blow-through of the parison during expansion and allows a uniform wall formation diminishing the possibility of establishing areas of varying wall thickness.

As the heated pressure medium is provided to the interior 134 of the parison 132 to a degree in excess of pressure in the interior 157 of the mold structure, the parison tends to expand and will initially expand downwardly to a point where the bottom panel 142 of the parison 132 contacts the bottom panel 154 of the mold structure. This initial expansion is primarily due to the ease at which the parison 132 will expand in this direction because of the bellows structure formed in the parison itself. At the time of initial expansion of the parison, the movable walls 160 are maintained inwardly toward the center portion of the mold structure 130 in order to prevent the outward expansion of the parison 132 toward the end walls of the mold structure. The expansion in this direction is actually inhibited until full expansion has been attained in the other two directions, downwardly and at right angles to the direction of expansion toward the movable walls 160. The downward expansion of the parison occurs with the material at a temperature slightly below the melting point of the crystalline structure, the molecules tend to align in chains in the direction of stretching of the material. The direction and amount of displacement will control the degree of orientation obtained.

As shown in FIG. 7, the parison has expanded fully downward and then referring to FIG. 8, the parison is then expanded outwardly at right angles to the direction of expansion toward the movable walls or transversely of the mold structure 130 with the movable walls 160 still maintained inwardly toward the center portion of the mold structure 130 thereby inhibiting the expansion of the parison outwardly toward the end walls 150 of the mold structure 130 or longitudinally of the mold structure 130. As the parison is initially expanded downwardly such that the upper panel 140 and lower panel 142 of the parison 132 are in contacting relation with the upper panel 148 and the lower panel 154 of the mold structure 130, the parison may then be expanded outwardly in lateral directions with the corrugation or bellows portion of the side walls of the parison 132 in aligned relation with the corrugation of the central portion 156 of the side walls 148 and the corrugation on the movable walls 160.

With the movable end walls 160 still positioned inwardly restricting the outward movement of the parison in a direction longitudinally of the mold structure 130, the parison is next expanded, as illustrated in FIG. 8, out- 9 wardly into contacting relation with the central portion 156 of the side walls 148 with the corrugations of the parison moving into mating engagement with the corrugations on the central portion 156 of the side walls 148. This subsequent stretching of the material at right angles to the initial direction of stretch tends to diminish, to a degree, the previous orientation of the molecular structure in the side wall area. The subsequent stretching tends to spread the initial chains and form chains at generally right angles to the initial chains. This chain formation, however, is not uniform in practice and results in a random pattern of aligned molecules with intersecting chains such that cleavage planes established by molecular orientation are reinforced by other alignments or chains thereby avoiding areas of weakness.

In order to provide the desired strength of the material in the bellows structure 10, a stretching of the material forming the pleats or corrugations of the bellows is conducted. The corrugations on the central portion 156 of the side walls 148 have cooling tubes 164 adjacent the ridge portions 155 to effect a heat transfer from the material as the material is moved into mating contacting relation with the corrugations to stabilize the material by lowering its temperature in this area. As expansion continues, the material in each pleat stretches outwardly to the outer apex of the pleat of the reservoir thereby tending to orient molecular chains from the apex of the valley toward the apex of the ridge of the bellows 10 of the reservoir 1 to resist hoop stresses created in container structures of this nature. The overall effect is to create areas having randomly oriented molecular structures which increase strength due to orientation without the effects of weakness caused by cleavage planes between aligned molecular chains.

With the parison 132 expanded vertically and transversely to the mold structure 130, the movable walls 160 are moved outwardly from the center portion of the mold structure 130 and the parison 132 is expanded outwardly into mating contacting relation with the corrugation on the movable end walls 160 to thereby complete the expansion of the parison into the final configuration of the collapsible reservoir 1. The cooling tubes 164 in the end walls 160 tend to stabilize the material of the forming reservoir as explained previously causing additional stretching of the material from the valleys to the ridges of the pleats of the bellows structure 10 of the reservoir 1.

It should be noted that throughout the entire expansion operation, the temperature of the parison is maintained at a point slightly below the melting point of the crystalline structure of said parison and a differential pressure is maintained between the interior of the parison and the exterior of said parison in order to effectively control the rate of expansion of said parison 132 and maintain the walls of the parison 132 in compression. Although the movement of the parison on expansion ofthe parison has been defined in steps, the overall process will be conducted quite quickly and from a practical standpoint, the expansion in the various directions will be almost simultaneous. It should also be noted that as the parison is expanded outwardly in all directions, there are no forces exerted on the parison which would tend to cause or effect a molecular alignment along a single plane. Although alignment does occur throughout the enclosed structure, this alignment is best described as random or along a plurality of intersecting planes in varying directions such that a single cleavage plane or a plurality of cleavage planes are not created across the enclosed structure, thereby effecting weaknesses in certain directions. This is particularly important in structures of this nature as various stresses will be applied in a plurality of directions and Where cleavage planes exist in this structure, failure at one time or another would be almost inevitable.

What I claim and desire to secure by Letters Patent is:

1. A variable volume reservoir in which the size changes to correspond to the quantity of material therein comprising:

(a) a first and second panel means, said panel means being disposed in spaced relation,

(b) wall means interconnecting said panels and being integrally formed therewith to form a monolithic enclosure, said wall means including a circumferentially extending bellows portion of flexible material to allow the relative movement of said panels inwardly and outwardly of one another, said bellows portion being of a flexible plastic of a crystalline structure and having a controlled molecular orientation, provided by forming the wall means and allowing it to set and then reheating same to a temperature near but below the melting point of the crystals and expanding the structure to stretch the wall means in one direction and then holding the panels while expanding the bellows portion to stretch same in directions in different planes to the first named stretch and then cooling the wall means to stabilize same in the expanded position,

(c) said bellows portion having alternating ridges and valleys wherein said molecular orientation includes orientation directed generally along lines extending from the valleys to the ridges and generally in the directions of the valleys.

2. A system for movement of a fiowable material comprised of:

(a) a liquid and air-tight variable volume reservoir for flexible material, said reservoir having first and second panel means and wall means, said wall means interconnecting said panel means and having a circumferentially extending bellows portion to form a container with flexible means on said wall means to permit the relative movement of said first and second panels inwardly and outwardly of one another,

(b) said bellows portion of the wall means being formed of a flexible plastic material of a crystalline structure with a plurality of oriented molecular chains disposed in random pattern, provided by forming the bellows portion and allowing it to set and then reheating same to a temperature near but below the melting point of the crystals and expanding the structure to stretch the bellows portion in one direction and then holding the panels while expanding the bellows portion to stretch same in directions indifferent planes to the first named stretch and then cooling the bellows portion to stabilize same in the expanded position,

(c) said bellows portion having alternating ridges and valleys wherein said molecular orientation includes orientation directed generally along lines extending from the valleys to the ridges and generally in the directions of the valleys,

(d) a discharge connection communicating with the reservoir,

(e) means operatively connected to said reservoir to provide relative movement between said panels to provide pressure on the fiowable material in said reservoir to effect flow of the material through said discharge connection.

References Cited UNITED STATES PATENTS 2,372,177 3/ 1945 Conner 222-107 3,186,600 6/1965 Guignard 222107 3,197,082 7/1965 Palombo 2222l5 X 2,432,025 12/1947 Lorenz 158-46 2,688,424 9/ 1954 Keiter 222-215 2,696,247 12/1954 Hiltner 15 850.1 X 2,784,882 3/1957 Du Bois 222215 (Other references on following page) 11 12 UNITED STATES PATENTS SAMUEL F. COLEMAN, Primary Examiner 3,083,877 4/1963 Gash 222 107 US Cl. 3,198,861 8/1965 Marvel 264-98 3,313,319 4/1967 Osborn et a1. 264-94X 3,350,492 10/1967 Grootenboer 264-320 5

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