US3351224A

US3351224A - Vacuum jacket construction

Info

Publication number: US3351224A
Application number: US374448A
Authority: US
Inventors: James H Anderson
Original assignee: Individual
Current assignee: Individual
Priority date: 1964-06-11
Filing date: 1964-06-11
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

NOV. 7, 1967 1 H, AAAAAA ON 3,351,224

ov` 7, 1967 J. H. ANDERSON 3,351,224

VACUUM JACKET CONSTRUCTION Filed June ll, 1964 3 Sheets-Sheet 2 INVENTOR ATTORNEYS Nov. 7, 1967 I J. H. ANDERSON VACUUM JACKET CONSTRUCTION 3 Sheets-Sheet I5 Filed June 1l, 1964 PI//W//f/M ATTORNEYS United States Patent O 3,351,224 VACUUM JACKET CONSTRUCTIGN James H. Anderson, 1615 Hillock Lane, York, Pa. 17403 Filed dune 11, 1964, Ser. No. 374,448 15 Claims. (Cl. 220-15) This invention relates to vacuum jackets for thermal insulation purposes and in particular to constructions for supporting a pipe or other vessel in spaced relation to an outer casing in a manner to reduce heat conduction between the pipe and the casing.

While vacuum jackets for reducing transfer of heat into or out of an inner container are well known, as for example in a Dewar flask, they do not wholly prevent heat transfer. One constructional feature of large vacuum insulated vessels which contributes to heat transfer across the vacuum is the mechanical supporting or spacing device which must be employed to maintain the inner vessel in spaced relationship to the outer casing. Any support must of necessity be secured to both the vessel and casing and thereby forms a bridge across the evacuated space through which heat may be conducted. In the case of heavy or bulky vessels or long pipe lines the supporting structure presents a serious heat leakage problem. More specifically, the problem exists in cryogenic Work and in the handling of liqueiied petroleum gases Where cold liquid is transported through pipe lines which must be of heavy construction to withstand the vapor pressure of the liquid.

Accordingly, it is the principal object of the present invention to provide an arrangement of an inner vessel and an outer casingwith a strong support which holds the vessel in spaced relationship to the casing and which is constructed in a manner to minimize heat leakage through the support.

It is a more specific object to provide a vessel and casing arrangement of the above type in which there is minimum surface contact between the supporting elements and the vessel and casing thereby minimizing the cross sectional area of material through which heat leakage can occur.

It is another object -to provide a jacket arrangement of the above type in which the length of the supporting structure is large compared to the distance between vessel and casing.

It is a further object to provide a jacket arrangement of the above type particularly suited to concentric pipes wherein the supporting structure includes flexible cables of low heat conductive material extending in tension between inner and outer pipes for suspending the vessel. Preferably the cables extend between radially spaced concentric supporting rings of low heat conductive material, the inner ring being secured to the exterior of the smaller pipe and the outer ring being secured to the inner surface of the larger pipe. Alternatively, the supporting structure for the cables may be a helix constructed of a material of low thermal conductivity and carried on the external surface of the inner pipe and a radially spaced helix of similar material engaging the inner surface of the outer pipe.

It is a fur-ther object to provide a method of assembling the just-mentioned concentric ring support which comprises assembling the inner pipe, concentric rings and supporting cables as a unit, sliding the outer pipe over the unit and expanding the outer rings into frictional engagement with the inner circumference of the outer pipe to thereby retain the inner pipe and outer pipes in fixed relationship.

Patented Nov. 7, 1967 ICC The invention will be further understood from the following detailed description in conjunction with the drawings in which:

FIGURE 1 is a side elevational view, partly broken away and partly in section, of concentric pipes supported in spaced relationship by a supporting arrangement constructed according to the principles of the present invention;

FIGURE 2 is a transverse sectional view taken on the line 2-2 of FIGURE l;

FIGURE 3 is a transverse sectional v-iew of a second embodiment of a supporting structure for concentric plpes;

FIGURE 4 is a transverse sectional view of a third embodiment of a supporting structure for concentric plpes;

FIGURE 5 is an exploded transverse sectional view of a fourth embodiment of a vsupporting structure for concentric pipes wherein the outer ring and the outer pipe are of split construction;

FIGURE 6 is a fragmentary longitudinal sectional view, similar to part of FIGURE 1, showing a second embodiment of outer ring construction;

FIGURE 7 is a sectional view, similar to FIGURE 6, showing a third embodiment of outer ring construction;

FIGURES 8 and 9 are fragmentary side elevational views, partly in section, showing fourth and fifth embodiments of outer ring constructions; and

FIGURE lO is a longitudinal sectional view of a vacuum flask showing a supporting structure constructed according to the principles of the invention.

Referring to FIGURES l and 2 there is shown an arrangement of inner and outer

concentric pipes

10 and 12 having an annulus 14 therebetween which is evacuated by means of a conventional vacuum pump 16. The system may be employed, for example, as a pipe line for long distance transporting of liquid petroleum gas, for transporting cryogenic iuids such as liquid oxygen or liquid nitrogen or for the handling of ordinary refr'gerant fluids. Alternatively, the construction may be employed for storage vessels for cold fluids.

The arrangement of FIGURES 1 and 2 is contemplated primarily as lan insulated pipe line for cold liquefied gas wherein the inner and

outer pipes

10 and 12 are constructed of metal having suicient strength to withstand the stresses resulting from the evacuation of the annulus 14 and the vapor pressure of the liquid in the inner pipe. The inner pipe 10 is suspended at the center of the outer pipe 12 by an arrangement which is analogous to the suspension of a hub Within the rim of a bicycle wheel. More specifically, the inner pipe 10 is suspended at a plurality of axially spaced locations by pairs of concentric flange-like elements or

rings

16, 18 having spoke-like cables 20 extending between the inner and

outer rings

16, 18 of each pair. The rings may be of metal, but preferably they are constructed of a high strength material of low heat conductivity, such as certain synthetic resins, and the cables are constructed off a material, such as glass bers, nylon or certain natural bers, which have high tensile strength and low heat conductivity. The inner rings 16 are secured to the exterior of the inner pipe 10 in any suitable manner as by bonding with a suitable bonding agent or by forcing the rings over the pipe 10 to form a tight fit.

The axially-facing edges of both inner and

outer rings

16, 18 are provided with a plurality of circumferentially spaced pins 22 which extend parallel to the axis of the

pipes

10, 12. The suspending cables 20 are then interlaced over a pin 22 on an outer ring 18 and under an adjacent pin 22 on the inner ring 16 of the same pair in a manner K to suspend the inner ring 16 and pipe 10 within the` outer ring 18. It is preferred to employ as long a length of cable as possible between pins in order to reduce as much as possible the amount of heat transferred through the material of the cable. T he` amount of heat transferred from the outer pipe 12 through a length of cable which connects two pins may be represented by the well known heat transfer equation where At is the temperature difference between one end of the cable length and the other end, k is the conductivity of the material of the cable, A is the cross sectional area of the cable and L is the length of cable between pins. Thus, as the length, L, is increased the amount of heat, q, conducted through the length is decreased. The maximum cable length between pins will occur when the length is about tangential to the inner pipe, although in practice it will often be desirable to employ a zig-zag pattern such as shown in FIGURE 2. The same equation indicates that the cross section of the cables 20 and the area of Contact between the cables 20 and pins 22 should also be made as small as possible. With respect to the latter feature it is desirable to approach point contact between the cables and the inner and outer pipe structures, although in practice it usually cannot be achieved.

Referring more specically to FIGURE 2 it will be seen that the cable pattern is established by providing an equal number of pins 22 on the inner and

outer rings

16, 18 of each pair with each pin 22 being opposite a corresponding pin 22 on the other ring. A rst cable 20 is then laced over a pin 22 on the outer ring 18, under a circumferentially spaced pin 22 on the inner ring 16, over a circumferentially spaced pin 22 on the outer ring, and so forth to connect every second pin on the outer ring 18 to every second pin on the inner ring 16. A second cable 20 is laced over the remaining pins 22 in a similar manner, and both cables 20 are then placed in tension, as by incorporating a turnbuckle (not shown), so that the assembly is stabilized against relative movement between the inner pipe and outer ring 18 regardless of the position of the assembly. The assembly may then be inserted longitudinally into the outer pipe 12 to complete the arrangement shown in FIGURES l and 2. If desired solid insulation (not shown) may be wrapped around the inner pipe 10 between the rings 16.

It will be seen that constructing the cables of relatively long lengths of high tensile strength material having a lower heat conductivity than metal and engaging them with only one side of each pin 22 provides a heat leakage path of very small capacity. While the use of pins 22 is very suitable for pipe line constructions, other mechanical arrangements may be employed so long as the arrangement minimizes contact between the cables 20 and their supports.

In the arrangement of FIGURE 3 an inner pipe 10a is suspended within an outer pipe 12a by means of a cable 20a which is laced between pins 22a on the inner and outer rings 16a, 18a in a manner such that its sections between pins 22a are generally tangential to the inner pipe 10a. While only a single cable 20a is shown, additional cables could be provided if desired.

In the arrangement of FIGURE 4 an inner horizontal pipe 10b is suspended within outer pipe 12b by a cable pattern which restrains substantially only downward movement of the inner pipe 10b. In addition, a concentric tubular insulating shield 24 of radiant heat reective material is supported by the cables 20b between the pipes. In this arrangement the cables are not laced lbetween alternate pins 22b but are anchored to the appropriate pins with mechanical fastening means or with a lbonding agent. The heatshield 24 is provided with suitable apertures 26ithrough which the cables pass, the latter supporting the shield 24 by engagement with the sides of the apertures 26. The shield 24 serves both to extend the length of the cables 20h to thereby reduce the amount of heat conducted through the cables and to reect heat being radiated by the outer pipe 12b. While only one reilective shield 24 is shown in FIGURE 4, additional concentric shields may be employed to achieve greater insulation. In sorne cases it may be desirable to provide longitudinally spaced rings in place of the shield 24 in which case the rings extend the path of the cables but do not themselves provide any signicant insulation.

FIGURE 5 illustrates an arrangement adapted for long pipe lines where it is not convenient to effect longitudinal movement between the outer pipe and the assembly of inner pipe, rings and cables. In the construction shown an inner pipe 10c is provided with xed axially spaced external rings 16cin the manner already described, and an outer pipe 12C is provided in a horizontally split form having an upper half 28 and a lower half 30. The lower half carries a plurality of axially spaced outer ring sections 32, the upper portions of which have been cut away. The cut-away portions are of suicient horizontal dimension to permit the lower pipe half 30 to be raised over the inner pipe 10c. The inner ring 16e and lower ring section 32 are provided with pins 22C in the samel manner as before so that one or more supporting cables 28C may be attached thereto to suspend the inner pipe 10c within the lower pipe half 30. An upper ring section 34 is then secured to the lower ring section 32 to bridge the cutaaway portion and thereby reinforce the lower section 32. The

ring sections

32 and 34 may be connected by means of mechanical fasteners such as pins, bolts or rivets or by means of a bonding agent or by welding if the rings are metal. The upper pipe half 28 is then placed over the assembly of

rings

16e and 32, 34 and inner pipe 10c, and the horizontal joints between the upper and lower pipe halves 28 and 30 are sealed as by welding. It may be desirable, in some instances, to employ pipe halves constructed of plastic material in which event they may be joined and sealed with a bonding agent.

FIGURE 6 illustrates an outer ring construction which is adapted to avoid jamming or other difficulties when an outer pipe 12d, of the type shown in FIGURE l, is slipped longitudinally over an assembly of an inner pipe 10d, inner and outer rings 16d and 18d and supporting cables 20d. It is obvious that variations in the transverse dimensions of the outer ring and the outer pipe will render final assembly diicult if the outer ring is sized to it closely within the outer pipe, but on the other hand it is desirable to maintain the clearance between rings and pipe as small as possible in order to prevent movement between the pipe and the other elements. In the construction of FIGURE 6, the outer ring 18d is constructed with a rather wide annular space 36 between it and the inner surface of the outer pipe 12d, and a mass of foamable plastic material 38, Afor example, in the form of a ring, is carried in the space 36. When the outer pipe 12d has been slipped over the inner elements, a torch or other heat source is applied to the circumferential portion of the outer pipe 12d opposite the foamable plastic 38 to cause the latter to expand andtll the annular space 36.

In the construction illustrated in FIGURE 6 the outer ring 18d is of somewhat corrugated shape in cross section with the foarnable plastic ring 38 being carried in a central depression 40 which forms a part of the space 36 between the ring 18d and the outer pipe 12d. On either side of the depression 40 is an outwardly bulging portion 42 which aids in retaining the plastic ring in place while the outer pipe 12d is being slipped into position. The inner ring 16d may be of any desired shape and, as shown, is of generally outwardly-facing channel construction having flan-ges which terminate in portions 44 which are spaced from and concentric with the inner pipe. The supporting cables 20d extend between these portions 44 and a corresponding portion of the outer ring 18d and are connected thereto in any convenient manner.

FIGURE 7 illustrates another arrangement in which an outer ring 18e is constructed considerably smaller than the inner diameter of an outer pipe 12e to permit easy positioning of the latter during assembly. In this construction, an inflatable ring 46 is carried in the annular space 36 between ring 18e and pipe 12e and is eX- panded to tightly engage both ring 18e and pipe 12e after the latter is in place. The inatable ring 46 may be a hollow sealed ring containing a cold liquefied gas which expands upon warming to inate the ring.

A different manner of locking an outer support ring to an outer pipe is illustrated in FIGURE 8 wherein the ring 18f is adapted to be mechanically expanded into tight engagement with the inner surface of the outer pipe. As shown, the ring 18f is constructed in a single split form having two opposing ends 48, 50 which can be forced apart by a wedge 52. A spiral tension spring 54 is connected at one end to a hook 56 on one of the ends of the ring and extends through a hole 58 in the wedge 52 to the larger end thereof where it terminates i-n an eye 60. A wire clip 62 passes through the eye and enga-ges the ends of the wedge 52 to urge it in a direction to expand the ring 181. Initially, as shown in FIGURE 8, the spring 54 will be restrained against drawing in the wedge 52 so that the ring 18f will be of considerably less diameter than the inside diameter of the outer pipe to permit the latter to be slid into position. This can be accomplished by forcibly extending the spring 54 and lling the hole 58 with a low melting point material 64, such as wax, which is solid at atmospheric temperatures and which can be melted by application of heat after the outer pipe has been positioned.

FIGURE 9 shows a split outer ring 18g which is adapted to be expanded into engagement with the inner surface of an outer pipe by means of a toggle linkage 66 carried on the inner periphery of the ring 18g. The linkage 66 is connected to the opposed ends of the ring by means of pivot pins 68 and 70 and extends across the gap between the ends. One of the toggle links includes an integral lever arm 72 which is movable in a direction to expand the toggle 66 (clockwise in FIGURE 9) by means of an actuating plunger 74. One end of the plunger 74 is pivoted to the end of the arm 72 by means of a pin 76 and the other end is carried within an openended cylinder 78. The other end of the cylinder 78 is pivoted at 80 to a bracket 82 which is carried by the ring 18g. A compressed gas, which may be in a liquid state, is contained within the cylinder 78. Initially, the plunger 74 is held in its retracted position against the pressure of the gas by a solid composition 84, such as wax, contained in the annulus between the plunger 74 and the cylinder 78. After an outer pipe has 'been slid over an inner assembly which includes the ring 18g, heat is applied to the exterior of the outer pipe near the cylinder 78 in order to melt the wax 84 and expand the gas. The plunger 74 is thereby extended and moves the arm 72 clockwise to expand the ring 18g. The length of the plunger 74 and the toggle 66 are constructed so that expansion of the gas will move the toggle 66 past its center position so that it becomes locked against free movement in an opposite direction. Any tendency of the plunger 74 to be retracted into the cylinder 78 by contraction of the gas is obviated by providing an aperture 86 in the cylinder -wall which allows most of the compressed gas to escape upon extension of the plunger 74.

While the pri-nciples of the invention are particularly concerned with horizontally elongated structures, such as concentric pipes, they are also applicable to other constructions such as the vacuum flask shown in FIGURE l0. In the construction illustrated the ask 88 is formed of spaced inner and outer

cylindrical shells

90, 92 joined integrally at their necks in a conventional manner. According to the invention the lower end of the inner shell is supported by means of a concentric ring and cable arrangement similar to those described above. An inwardly facing channel-shaped plastic ring 94 is bonded to the inner ysurface of the outer shell 92, and a somewhat similar plastic ring 96 of greater vertical dimension is bonded to the lower end of the inner shell 90. Preferably the inner ring 96 is contoured to engage both a portion of the cylindrical side wall and a portion of the horizontal wall of the inner shell 90 in order to provide maximum support for the latter. Nylon cables 98 under tension, are provided between the

adjacent flanges

100, 102 of the two rings so that an upward force is exerted on the inner shell 90 to yreduce stress at the neck.

Thus, it will be appreciated that the present invention provides a support arrangement for the inner and outer members of a vacuum jacket which reduces heat leakage through the support to a minimum. The reduction in heat leakage is achieved by a combination of features which include the use of relatively low heat conducting materials, the provision of long spoke-like supporting elements of relatively small cross section in a plane transverse to the direction of heat leakage and the provision of a relatively small area of contact between the spoke-like supporting elements and the jacket members. While the illustrated supporting elements are constructed of flexible cables of glass fiber or nylon, it is contemplated that more rigid elements such as thin rods of plastic material or ceramic material are suitable for some applications. In addition, the shape of the supporting rings may be varied to achieve the lowest area of contact with the pipes and supporting spokes which is consistent with the necessary strength. The concentric rings are not per se required, except as supports for the spokes, and in some installations one or both of them may be dispensed with if the spokes can be attached directly to the inner and outer jacket members. Accordingly, the details of the embodiments shown in the drawings are intended as illustrative and not limiting except as they appear in the appended claims.

What is claimed is:

1. A double walled heat insulating vessel or the like comprising: an inner wall structure `defining a space for containing material to be insulated from ambient temperatures; an outer wall structure at least partially surrounding said inner wall structure and spaced therefrom and defining therewith a space adapted to be evacuated in order to reduce heat transfer between the walls; supporting means between said inner wall and said outer wall, said supporting means including a plurality of mutually spaced spoke-like elements extending between and attached to the exterior surface of said inner wall structure and to the interior surface of said outer wall structure, said spoke-like elements being the sole suspending interconnection between said wall structures and being defined by at least one tensioned cable constructed of a material having high tensile strength and a heat conductivity lower than that of metal, said cable passing through a concentric tubular heat shield at a plurality of circumferentially spaced apart locations and being deflected by said heat shield thereby increasing the length of the cable between successive points of attachment and thereby providing a long heat conduction path between said wall structures.

2. Apparatus as in claim 1 wherein said shield is constructed of radiant heat reilective material and is provided with apertures through which said cable extends, said cable engaging the sides of said openings to thereby support said shield.

3. A suspension structure for thermally insulating and supporting a conduit-like member comprising a first hollow ring member adapted to surround and be held in supporting engagement with the periphery of the conduit-like member; a second hollow ring member whose inner dimension is greater than the outer dimension of said first ring member surrounding said iirst ring member and adapted to be held in supporting engagement with internal surfaces of a conduit housing, each of said ring members carrying a set of cable securing protuberances at spaced apart positions; and at least one tensioned cable of a material having high tensile strength and a lower heat conductivity than metal laced between the protuberances of one set and the protuberances of the other set so as to suspend said inner ring member within said outer ring member, said cable being the sole suspending interconnection between said ring members whereby reduced heat conduction from one ring member to the other through said cable is effected as a result of the reduced area of contact between said cable and said protuberances. p

4. Apparatus as in claim 3 wherein the length of said cable between successive protuberances is substantially greater than the minimum distance between said first and second ring members thereby providing a long heat conduction path between said ring members.

5. Apparatus as in claim 4 wherein said protuberances are pin-like elements extending from said ring members parallel to the axes of said ring members,

6. Apparatus as in claim 5 further including at least one concentric tubular heat shield between said first and second ring members, said cable passing through said shield at a plurality of circumferentially spaced apart locations and being deected by said shield thereby increasing the length of the cable between successive pins.

7. Apparatus as in claim 5 wherein said second ring member is radially expansible so as to be capable of expanding into engagement with internal surfaces of the conduit housing.

8. Apparatus as in claim 7 wherein said second ring member includes at its periphery an inatable member which expands radially when inated.

9. A suspension structure for thermally insulating and supporting a conduit-like member comprising a hollow radially expansible ring structure adapted to tit loosely within a conduit housing and adapted to be supported by engagement with internal surfaces of the conduit housing when expanded; cable attaching means carried by said ring structure at a plurality of circumferentially spaced apart points on said ring structure; and at least one cable of low heat conductivity extending from said cable attaching means and adapted to suspend the conduit-like member within said ring structure whereby an assembly of said 8. ring structure with the conduit-'like member may be moved longitudinally into the conduit housing and secured therein by radially expanding said ring structure.

10. Apparatus as in claim 9 wherein said ring struc-` ture includes a rigid ring member and a radially expansible member carried on the periphery of said ring member.

11. Apparatus as in claim 9 wherein said radially expansible member includes a mass of foamable plastic material.

12. Apparatus as in claim 9 wheren said radially expansible member includes a duid-tight ilexible inflatable member.

13. Apparatus as in claim 9 wherein said ring structure includes a split ring member having two opposed ends,

a toggle linkage connecting said ends and means actuating p said toggle linkage to move said ends away from eachV other.

14. Apparatus as in claim 10 wherein said radially` expans'ible member is generally ring shaped and is coaxial ieferences Cited UNlTED STATES `PATENTS 1,761,084 6/1930 Lissauer 138-113 1,863,958 6/1932 Wulff et al. 220-15 1,866,517 7/1932 Heylandt 220--15 1,918,335 7 1933 Heylandt 220-9 2,057,346 10/1936 Reed 22015 2,868,230 1/11959 Stokes 138-113 3,004,683 10/1961 Buchhold et al. 220--15 3,064,317 11/ 1962 Dobson. 3,078,004 2/ 1963 Randolph 220-#15 X 3,110,324 11/1963 DeHaan 1384114 X FOREIGN PATENTS 573,596 4/1959 Canada. 636,523 2/1962 Canada.

THERON E; CONDON, Primary Examiner. JAMES R.' GARRETT, Examiner.

Claims

1. A DOUBLE WALLED HEAT INSULATING VESSEL OR THE LIKE COMPRISING: AN INNER WALL STRUCTURE DEFINING A SPACE FOR CONTAINING MATERIAL TO BE INSULATED FROM AMBIENT TEMPERATURES; AN OUTER WALL STRUCTURE AT LEAST PARTIALLY SURROUNDING SAID INNER WALL STRUCTURE AND SPACED THEREFROM AND DEFINING THEREWITH A SPACE ADAPTED TO BE EVACUATED IN ORDER TO REDUCE HEAT TRANSFER BETWEEN THE WALLS; SUPPORTING MEANS BETWEEN SAID INNER WALL AND SAID OUTER WALL, SAID SUPPORTING MEANS INCLUDING A PLURALITY OF MUTUALLY SPACED SPOKE-LIKE ELEMENTS EXTENDING BETWEEN AND ATTACHED TO THE EXTERIOR SURFACE OF SAID INNER WALL STRUCTURE AND TO THE INTERIOR SURFACE OF SAID OUTER WALL STRUCTURE, SAID SPOKE-LIKE ELEMENTS BEING THE SOLE SUSPENDING INTERCONNECTION BETWEEN SAID WALL STRUCTURES AND BEING DEFINED BY AT LEAST ONE TENSIONED CABLE CONSTRUCTED OF A MATERIAL HAVING HIGH TENSILE STRENGTH AND A HEAT CONDUCTIVITY LOWER THAN THAT OF METAL, SAID CABLE PASSING THROUGH A CONCENTRIC TUBULAR HEAT SHIELD AT A PLURALITY OF CIRCUMFERENTIALLY SPACED APART LOCATIONS AND BEING DEFLECTED BY SAID HEAT SHIELD THEREBY INCREASING THE LENGTH OF THE CABLE BETWEEN SUCCESSIVE POINTS OF ATTACHMENT AND THEREBY PROVIDING A LONG HEAT CONDUCTION PATH BETWEEN SAID WALL STRUCTURES.