SOLAR-ENERGY-CONCENTRATING DEVICE

• US 3,613,659 A
• Filed: 10/14/1968
• Issued: 10/19/1971
• Est. Priority Date: 10/14/1968
• Status: Expired due to Term

• Current Assignee: Robert M. Phillips
• Original Assignee: Robert M. Phillips
• Inventors: Phillips, Robert M.
• Primary Examiner(s): Myhre, Charles J.
• Application Number:
  US04/767,072
• Time in Patent Office: 1,100 Days
• Field of Search: 126/270,271 350/292
• US Class Current: 126/605
• CPC Class Codes: F24S 20/30 Solar heat collectors for heating objects, e.g. solar cookers or solar furnaces
• CPC Class Codes: F24S 2020/16 Preventing shading effects
• CPC Class Codes: F24S 2030/131 in the form of articulated bars
• CPC Class Codes: F24S 2030/14 Movement guiding means
• CPC Class Codes: F24S 23/80 having discontinuous faces
• CPC Class Codes: F24S 23/82 characterised by the material or the construction of the reflector
• CPC Class Codes: F24S 25/10 extending in directions away from a supporting surface
• CPC Class Codes: F24S 25/70 with means for adjusting the final position or orientation of supporting elements in relation to each other or to a mounting surface; with means for compensating mounting tolerances
• CPC Class Codes: F24S 30/455 Horizontal primary axis
• CPC Class Codes: F24S 50/20 for tracking
• CPC Class Codes: G01S 3/7861 Solar tracking systems
• CPC Class Codes: Y02A 40/926 Cooking stoves or furnaces using solar heat
• CPC Class Codes: Y02E 10/47 Mountings or tracking

Abstract

Presented is a solar-energy-concentrating device in which a reflector-concentrator panel is supported in such manner that radiant solar energy is intercepted by the reflector-concentrator panel and reflected onto a proportionately smaller radiantenergy-absorbing surface. The radiant-energy-absorbing surface and concentrator panel are supported in relation to each other so that the shadow cast by the radiant-energy-absorbing surface typically does not fall upon the reflective surface of the concentrator panel so as to preclude interference with reflection of radiant energy thereby. The concentrator panel may be in the form of a single module having a concentration ratio with respect to the radiant-energy-absorbing surface ranging between 6 1/2 -12 to 1, and preferably closely approximating 10 to 1; or it may be in the form of a plurality of such modular panels arranged to provide a selected concentration ratio or permit adjustment of the temperature of the absorbing surface through independent adjustment of one or more of the panels. For concentration ratios falling into this preferred range, it has been found that the operating temperature of the radiant-energy-absorbing device or surface will selectively range between 350* F. and 500* F. In another embodiment the reflector-concentrator panel is provided with a reflective surface each increment of which is related to adjacent incremental surface areas so as to provide the desired predetermined concentration ratio. The radiant-energy-absorbing surface may be one surface of a flat plate arranged to absorb the radiant energy from the sun that is reflected to it by the concentrator panel, the heat from which may in turn be utilized for any appropriate purpose requiring a source of heat, as for instance to heat the interior of an oven chamber formed by placing an appropriate cover structure over the plate. The radiant-energy-absorbing surface is supported on a suitable frame in adjustable relation to the reflector-concentrator panel so that in all positions of the frame, giving effect to adjustments required to place the reflecting surface of the concentrator panel in relation to the sun so as to secure maximum efficiency, the radiant-energy-absorbing surface is maintained in a horizontal position so as to conveniently support objects thereon in heat transfer relation to the radiant-energy-absorbing surface.

Claims

1. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means interposed between said radiant-energy-absorbing device and said support frame to maintain said radiant-energyabsorbing device horizontal.

2. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimensioN;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. said reflector-concentrator panel, said radiant-energy-absorbing device and said support frame being pivotally interconnected and selectively collapsible into a compact package.

3. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means thermally insulating at least one surface of said radiant-energy-absorbing device from the ambient atmosphere.

4. The combination according to claim 3, in which said reflector-concentrator panel constitutes a generally rectangular slab of material a surface portion of which is formed with a multiplicity of transversely extending steps, the primary face of each said step being angularly disposed to the primary face of an adjacent step, and a thin reflective film draped over said slab so as to conform to said steps to provide a multiplicity of separate reflective surfaces the degree of convergence of radiant energy reflected therefrom being in the order of magnitude of from 6 to 12:

1.

5. The combination according to claim 3, in which said reflector-concentrator panel comprises a relatively flat slab of material the reflective surface of which is provided with a multiplicity of indentations arranged in two groups on opposite sides of a median plane, the indentations of each group ranging from a relatively shallow indentation adjacent said median plane to a relatively deep indentation adjacent the end of said slab.

6. The combination according to claim 3, in which said reflector-concentrator panel constitutes a monolithic slab of expandable-bead type material, one surface of which is formed to provide a pair of aligned series of transversely extending and longitudinally recurrent angularly disposed stepped surfaces, in each series the angular disposition of the stepped surfaces being such that corresponding stepped surfaces adjacent opposite ends of the reflector-concentrator panel reflect radiant energy from the sun to a common surface area on said radiant-energy-absorbing device.

7. The combination according to claim 3, in which said radiant-energy-absorbing device includes a relatively flat plate suspended on said support frame so that the plate is normally disposed in a horizontal plane during use.

8. The combination according to claim 3, in which said radiant-energy-absorbing device comprises a relatively flat plate suspended on said frame, and means are detachably secured adjacent said flat plate on the side thereof next adjacent said reflector-concentrator panel forming a transparent window through which said solar radiations pass to reach said flat plate.

9. The combination according to claim 3, in which said radiant-energy-absorbing device includes a frame member, and a flat plate thermally insulated from the frame member and supported thereon to absorb said solar radiations focused thereon.

10. The combination accOrding to claim 3, in which said radiant-energy-absorbing device includes a frame member, a flat plate detachably supported on one side thereof to absorb solar radiations focused thereon, and a transparent window detachably supported on the other side of said frame to thermally insulate the flat plate from the ambient atmosphere.

11. The combination according to claim 3, in which said radiant-energy-absorbing device includes a flat plate supported on the support frame in position to absorb solar radiations focused thereon, a transparent window supported adjacent one side of said plate to shield the associated side of the plate from the ambient atmosphere, and an enclosure supported adjacent the opposite side of said flat plate from the transparent window to shield said opposite side thereof from the ambient atmosphere.

12. The combination according to claim 3, in which said support frame includes an auxiliary brace one end of which is adjustably pivoted to said support frame and the other end of which is pivotally attached to said reflector-concentrator panel.

13. The combination according to claim 3, in which said support frame includes an auxiliary brace one end of which is pivotally connected to said support frame intermediate its ends, and the other end of which is adjustably connected to said reflector-concentrator panel intermediate its ends, one end of said reflector-concentrator panel being pivotally attached to said support frame adjacent one end thereof.

14. The combination according to claim 3, in which said support frame includes a first U-shaped member, a second U-shaped member, brace means interposed between said U-shaped members, and means interposed between said support frame, brace means and reflector-concentrator panel operable to selectively collapse the support frame, brace means and reflector-concentrator panel into a flat package.

15. The combination according to claim 3, in which said support frame includes a main support post adapted to be supported in an upright position, brace means angularly disposed with respect to said main support post so that said brace means lies in substantially the same plane with said main support post, means adjustably connecting the lower end of said brace means with said main support post intermediate its ends and with one end of the reflector-concentrator panel, the other end of said reflector-concentrator panel being supported adjacent the lower end of said brace means.

16. The combination according to claim 3, in which said means for thermally insulating at least one surface of said radiant energy absorbing device comprises a window transparent to solar radiations interposed between said radiant-energy-absorbing device and said reflector-concentrator panel.

17. The combination according to claim 3, in which said means for thermally insulating at least one surface of said radiant-energy-absorbing device comprises an enclosure mounted on the side of said radiant-energy-absorbing device remote from said reflector-concentrator panel.

18. The combination according to claim 3, in which said means for thermally insulating said radiant-energy-absorbing device from the ambient atmosphere includes a window transparent to solar radiations detachably interposed between said radiant-energy-absorbing device and said reflector-concentrator panel, and an enclosure mounted in association with the surface of said radiant-energy-absorbing device remote from said transparent window.

19. The combination according to claim 4, in which said thin reflective film draped over said slab comprises a thin film of synthetic resinous material sufficiently pliable to conform to the configuration of said transversely extending steps, and a thin layer of reflective metal on said film of synthetic resinous material effective to intercept and reflect said solar radiations.

20. The combination according to claim 5, in which corresponding indentations on opposite sides of said median plane are angularly diSposed so that radiant energy from the sun incident thereupon is reflected onto a common surface area on said radiant-energy-absorbing device.

21. The combination according to claim 6, in which the width of the beam in the longitudinal (X) dimension measured at the radiant-energy-absorbing device approximates the width of one of said stepped surfaces of the reflector-concentrator panel.

22. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. said radiant-energy-absorbing device including a relatively flat plate suspended on said frame, and means are detachable superimposed over said flat plate to define an oven enclosure.

23. The combination according to claim 22, in which said means detachably superimposed over said flat plate to define an oven enclosure comprises a sheet of material having high resistance to thermal conductivity folded to form a hollow body supportable in association with said radiant-energy-absorbing device to enclose one surface thereof.

24. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cost by said radiant energy absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. said reflective surface including at least two reflective surface portions, one of said reflective surface portions being associated with one end of the reflector-concentrator panel and the other reflective surface portion being associated with the opposite end of the reflector-concentrator panel;

e. said reflective surface portions being inclined in opposite directions.

25. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. said reflector-concentrator panel comprising a pair of reflective surfaces arranged in side-by-side relation and arranged so that solar radiations reflected from both said reflective surfaces are focused upon said radiant-energy-absorbing device;

e. and a pair of radiant-energy-absorbing devices each associated with one of said pair of reflective surfaces.

26. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

B. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. said reflector-concentrator panel comprising a pair of reflective surfaces arranged in side-by-side relation and arranged so that solar radiations reflected from both said reflective surfaces are focused upon said radiant-energy-absorbing device;

e. said pair of reflective surfaces being normally adapted to be focused on adjacent areas of said radiant-energy-absorbing device, and means for adjusting said reflective surfaces so that both reflective surfaces are focused in superposed relation upon a common area of said radiant-energy-absorbing device.

27. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means adjustably interconnecting said reflector-concentrator panel and support frame and selectively operable to adjust the position of the reflector-concentrator panel in relation to the sun;

e. said means adjustably interconnecting said reflector-concentrator panel and support frame including means for tracking the sun in its azimuthal and elevational variations in position, and means responsive to said tracking means to effect automatic adjustment of the reflector-concentrator panel in relation to movement of the sun.

28. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means rotatably supporting said support frame for rotation about a vertical axis;

e. said means for rotatably supporting said support frame comprising a collapsible pedestal including a pair of relatively rotatably members selectively adjustable into cruciform relationship when in use and adjustable into axial alignment when not in use, and a socket member mounted on said pedestal engageable by a depending portion of said support frame.

29. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said refleCtor-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means rotatably supporting said support frame for rotation about a vertical axis;

e. said means for rotatably supporting said support frame comprising a pointed stake adapted to be driven into the ground, a flange on the stake for limiting penetration of said stake into the ground, a bearing shoulder on said stake adjacent said flange engageable by said frame, and a head mounted on said stake spaced from and cooperating with said bearing shoulder to rotatably support said frame member.

30. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means rotatably supporting said support frame for rotation about a vertical axis;

e. said means for rotatably supporting said support frame comprising an elongated stake having a cylindrical mounting portion at one end and a pointed driving portion at the other end adapted to be driven into the sand to support said support frame.

31. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means operatively associated with said reflector-concentrator panel manipulable to effect optimum focusing of the reflected radiant energy on the radiant-energy-absorbing device;

e. said means operatively associated with said reflector-concentrator panel to effect optimum focusing of the reflected radiant energy comprising a focusing cell including a U-shaped frame member having a pair of parallel arms one of which is apertured to admit a beam of light and the other of which includes a target thereon upon which the beam of light passing through said aperture impinges when said reflector-concentrator panel is properly positioned in relation to the sun so as to focus the radiant energy therefrom on said radiant-energy-absorbing device.

32. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means operatively associated with said reflector-concentrator panel manipulable to effect optimum Focusing of the reflected radiant energy on the radiant-energy-absorbing device;

e. said means to effect optimum focusing of the reflected radiant energy including a pair of motors, a control circuit including a source of electrical energy connected to said motors and including a plurality of heat-responsive switches, one of said motors being operatively connected to said reflector-concentrator panel to effect adjustment thereof to compensate for azimuthal variations of the sun and the other of said motors being operatively connected to said reflector-concentrator panel to effect adjustment thereof to compensate for elevational variations in the position of the sun, activation and deactivation of said heat-responsive switches being automatically controlled by variations in the sun'"'"''"'"'s position to effect substantially automatic tracking of the sun by said reflector-concentrator panel.

33. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means operatively associated with said reflector-concentrator panel manipulable to effect optimum focusing of the reflected radiant energy on the radiant-energy-absorbing device;

e. said means for effecting optimum focusing of the reflected radiant energy including a pair of motors connected to said reflector-concentrator panel and effective when energized to adjust the position of the reflector-concentrator panel to compensate for azimuthal and elevational variations in the position of the sun, control means including a circuit having a plurality of transistors connected to said motors, and a plurality of light-sensitive photocells in said control circuit mounted in operative association with said reflector-concentrator panel and responsive to a shaft of light to effect biasing of said transistors and actuation of said motors to effect adjustment of said reflector-concentrator panel in correlation to the azimuthal and elevational variations in the position of the sun.

34. A solar-energy-concentrating device comprising:

a. a reflector-concentrator panel including a reflective surface having a longitudinal (X) dimension and a transverse (Y) dimension;

b. a support frame to support the reflector-concentrator panel in position to intercept and reflect solar radiations;

c. and a radiant-energy-absorbing device operatively associated with the frame and upon which the reflected solar radiations are focused, said radiant-energy-absorbing device being spatially related to said reflector-concentrator panel so that the shadow cast by said radiant-energy-absorbing device normally does not fall upon the reflective surface of said reflector-concentrator panel;

d. and means operatively associated with said reflector-concentrator panel manipulable to effect optimum focusing of the reflected radiant energy on the radiant-energy-absorbing device;

e. said means to effect optimum focusing of the reflected radiant energy including a pair of motors operatively connected to said reflector-concentrator panel to effect adjustment thereof to compensate for azimuthal and elevational variations in the position of the sun, a circuit connected to said motors for controlling energization thereof, said circuit including a plurality of heat-responsive switches arranged to operate in response to heat applied thereto, and means including a lens interposed between said Heat-responsive switches and the sun to focus the sun'"'"''"'"'s rays selectively on one or the other of said heat-responsive switches in correlation to azimuthal and elevational variations in the position of the sun.

35. As an article of manufacture, a solar-energy-absorbing device for use in conjunction with a solar-energy-concentrating device and comprising:

a. a flat radiant-energy-absorbing plate;

b. a support frame spaced about said plate; and

c. means operatively interposed between said plate and said support frame to detachably interconnect the plate to the support frame and thermally insulate the support frame from the plate;

d. said radiant-energy-absorbing plate being detachably mounted on one side of said support frame, and a radiant energy transparent window detachably mounted on the opposite side of said support frame from said radiant-energy-absorbing plate.

36. The combination according to claim 35, in which said radiant-energy-absorbing plate is rectangular and apertured adjacent each corner, and thermally insulating bushing means are provided extending through each said aperture and thermally insulating said support frame from said plate.

37. The combination according to claim 35, in which said support frame includes a radially inwardly extending flange, said radiant-energy-absorbing plate is detachably mounted on said radially inwardly extending flange, and an enclosure is superimposed over said radiant-energy-absorbing plate and detachably supported on said radially inwardly extending flange.

38. As an article of manufacture, an enclosure for converting a hot plate on which food to be cooked is directly supported into an oven comprising:

a. a hollow body having a top, sidewalls depending from said top, said body on the side thereof opposite said top being open and adapted to be closed by said underlying hot plate, said hollow body being formed from a material having a low coefficient of thermal conductivity.

39. The combination according to claim 38, in which selected areas of said hollow body are provided with punchout areas the peripheries of which are defined over a substantial portion thereof by slits extending through the wall of said hollow body.

40. The combination according to claim 38, in which said hollow body is formed from a flat sheet portions of which are folded to provide said top and sidewalls, and means are provided interposed between selected sections of said sidewalls to retain the hollow body in folded condition.

41. The combination according to claim 38, in which said sidewalls on the edges thereof remote from said top wall are provided with outwardly extending flanges forming an integral portion of the associated sidewall.

42. The combination according to claim 38, in which said hollow body is formed from a flat blank fabricated from a material having a low coefficient of thermal conductivity, score lines formed in said sheet material defining said top and sidewalls, triangular tab means integrally interposed between the end edges of adjacent sidewalls, score means bisecting said triangular tab means, and means joining corresponding pairs of said tab means at opposite ends of said body to the associated end wall thereof.

43. The combination according to claim 40, in which said means retaining said sheet in folded condition constitutes an adhesive applied to selected areas of said sheet and adherent to associated adjacent areas of the sheet to retain the sheet in folded condition.

44. The combination according to claim 40, in which said means for retaining said folded sheet in folded condition includes apertures formed in said sheet in a predetermined pattern so that said apertures register one with the other when said sheet is folded, and brad means detachably retained in said registered apertures to retain the sheet in folded condition.

45. The combination according to claim 38, in which the interior of said hollow body is lined with a heat-reflective matErial.

46. The combination according to claim 38, in which said hollow body is formed in final configuration from cellulosic material having a low coefficient of thermal conductivity by depositing finely comminuted cellulosic material upon a form conforming to the final configuration of said hollow body to form a mat, treating said mat to render said mat dimensionally stable in its final configuration, and removing the finally configured hollow body from said form.

47. The combination according to claim 46, in which said cellulosic material is applied to said form as an aqueous slurry, and said treatment for effecting dimensional stability of said mat comprises driving the water from said cellulosic material.