Method and apparatus for manufacturing solar heater panels

A method and apparatus for assembling a fluid conducting tubular member into secure engagement with a channel integral with an elongated solar heat absorbing plate. The apparatus includes an elongated inflatable tube secured to an upstanding wall fastened to a table top. A fixture having a shallow V-shaped concave face is mounted on said table top with the concave face adjacent and parallel to said tube. An elongated plate having a channel parallel with the longer plate edges is positioned between the tube and the fixture with the channel opening toward the fixture. When the tube is inflated, it presses the plate toward the concave fixture surface. Plate edges contact and are restrained by the fixture edges, while the center of the plate is free to move further toward the fixture, flexing the plate in a manner increasing the diameter of the channel. A tubular member having an outside diameter equal to or greater than the unflexed channel diameter is inserted into the channel. When the tube is deflated, the plate returns to the unflexed state. The tubular member is thus firmly held in the channel, providing a rigid and secure assembly, with excellent heat transfer characteristics.

BACKGROUND OF THE INVENTION 
This invention relates in general to solar energy hearing equipment and, 
more specifically, to a method and apparatus for manufacturing solar 
heater panels for use in such equipment. 
Many different types of solar energy collecting systems have been devised, 
with a variety of means for conducting the collected heat into a working 
fluid. One system which has been found to be very effective is described 
in U.S. Pat. No. 4,011,856, assigned to the assignee of this application. 
The system disclosed by that patent uses solar heating panels consisting 
of elongated plates, each having a channel along the plate centerline into 
which is secured a fluid carrying tubular member. Solar radiation falling 
on the plates is absorbed and conducted to the tubular members, and then 
to a working fluid flowing through the tubular members. For efficient 
operation, the tubular members must be securely held in the channels, with 
the inner surfaces of the channels and the outer surfaces of the tubular 
members in tight contact for good conductive heat transfer. 
Many methods and apparatuses have been developed for fastening plates or 
fins to tubes for use in heat exchangers or other devices. Often, tubes 
are welded, soldered or brazed to plates or fins. Thin walled tubes are 
often damaged during welding or forming operations required in these 
methods. Also, these methods tend to produce relatively small contact 
areas between plate and tube. 
Sandberg, in his U.S. Pat. Nos. 2,585,043 and 2,666,981, presses tubes into 
shallow grooves in metal sheets, forcing the tube into the sheet to form a 
tube holding channel. The apparatus required to do this is complex, 
cumbersome and slow. Also, since this technique requires the tube to act 
as the sheet deforming tool, the tube is likely to be deformed, damaged or 
cracked during the forming operation. Even with heavy walled tubes and 
thin sheets there is substantial risk of damage to the tubes. The Sandberg 
method and apparatus is not suitable for use with a combination of thin 
walled tubes and thick plates of the sort used in solar heater panels. 
These prior methods and apparatus for forming finned tubes are generally 
incapable of manufacturing solar heating panels which require the use of 
relatively thick fins and thin tubes with large areas of physical contact 
between fin and tube. Thus, there is a continuing need for improved 
methods and apparatuses for manufacturing solar heating panels. 
SUMMARY OF THE INVENTION 
The problems noted above, and others, are overcome by our apparatus and 
method for rapidly inserting a tubular member into a channel formed in an 
elongated plate. Basically, the apparatus comprises an elongated 
inflatable tube secured along an upstanding wall running along a table 
surface, with a fixture adjacent to the tube having a concave, shallow 
V-shaped, face parallel to and slightly spaced from said table. An 
elongated plate having a generally cross-section channel parallel to one 
of the longer plate edges, is placed between tube and fixture with the 
opening of the channel toward the fixture. When the tube is inflated, it 
presses against the plate, bringing plate edges into restraining contact 
with the fixture. Since the center of the plate remains free to move 
further, it is flexed slightly, increasing the diameter of the channel. A 
tubular member having an outside diameter equal to or slightly greater 
than the unflexed channel diameter may then be easily inserted into the 
channel. Upon deflation of the tube, plate elasticity returns the channel 
to its original diameter, tightly engaging the tubular member around a 
large part of its circumference.

DETAILED DESCRIPTION OF THE INVENTION 
Referring now to FIG. 1, there is seen a table top 10, mounted in a 
conventional manner on a plurality of legs 12. Table top 10 may be of any 
suitable construction (wood, metal, etc.) providing rigid support to the 
structures to be fastened thereto. 
An elongated wall 14 is secured to table top 10 by any conventional means, 
such as bolts 15. In the embodiment illustrated, wall 14 is a standard 
rectangular box section structural member. Two elongated tubes 16 are 
arranged in flattened condition along the two sides of wall 14. Of course, 
a single tube 16 could be used along only one side of wall 14, cooperating 
with one of the pair of cooperating fixtures discussed below. For maximum 
convenience and highest production rates, the pair of tubes shown is 
preferred. One end of each tube 16 is sealed, such as by a suitable 
rubber-based adhesive, and fastened to wall 14 by any conventional means, 
such as bolts 18. The opposite end of each tube 16 is similarly fastened 
by bolts 38 to wall 14, as seen in FIG. 4. 
Adjacent and parallel to each tube 16 is a fixture 20, secured to table top 
10 by any conventional means, such as bolts 22. Knee braces 24 further 
support fixtures. Bolts 25 fasten knee braces 24 to table top 10 and 
fixtures 20. As described in further detail below, fixtures 20 have 
concave, shallow V-shaped, faces opposite tube 16. End caps 26 cover the 
right ends of fixtures 20 as seen in FIG. 1. 
Air for inflating tubes 16 is conducted from a conventional air supply 
through hose 28 to a control box 30 mounted along the edge of table top 
10. A gauge 32 monitors available air pressure. A pair of conventional air 
valves within box 30 are operated by three-position control knobs 34 to 
control admission of air to tubes 16 through hoses 35 and connectors 36. 
The air valves (not shown) within box 30 are movable between an "off" or 
closed position in which no air flows through hoses 28 and 35, an 
"inflate" position in which hose 28 is connected to one or both of hoses 
35 and a "deflate" position in which the end of hose 28 is closed but 
hoses 35 are open to the atmosphere, releasing air in tubes 16 through 
hoses 35. If desired, box 30 may also enclose convnetional air filters, 
pressure regulators, air moisture removing means, etc. 
As shown in FIG. 4, the end of tubes 16 through which air is admitted are 
secured to wall 14 by bolts 38, with the end of tube 16 adhesively sealed 
around a stem 40. Knobs 34 control the air valves described above to admit 
air into tubes 16 or exhaust air from tubes 16 to the atmosphere. 
Tubes 16 may be formed from any suitable material. Typical materials 
include rubberized fabric materials of the sort used in most fire hoses, 
reinforced rubber or plastic material, etc. The tube material should be 
sufficiently strong to resist balooning beyond a fully circular 
cross-section while being sufficiently flexible or elastic to rapidly 
deflate when the internal air pressure is released. Since these properties 
are best found in the rubberized fabrics used in light-weight fire hoses, 
such materials are preferred for tubes 16. 
FIGS. 2A and 2B illustrate the function of the apparatus of this invention. 
A typical solar heater plate 42 of the type suitable for use in the solar 
fluid heater shown in U.S. Pat. No. 4,011856 is shown in end view in FIG. 
2A. This plate is approximately flat, although the edges of the plate are 
preferably slightly curved or bent as shown. While for the purposes of 
this invention plate 42 is referred to as "approximately flat," it should 
be recognized that the edges of plate 42 may be bent slightly toward the 
channel side (as seen in FIG. 2A) or, conversely, could be bent slightly 
in the opposite direction, if desired. The angle selected for the walls of 
the shallow V-shaped concavity in the face of fixture 20 will depend on 
the angle of the edges of plate 42. The important factor is that the edges 
of plate 42 contact the concave fixture face before the central or 
channeled portion of plate 42 contacts the face. Channel 44 is formed 
parallel to the longer edges of plate 42. While channel 44 is preferably 
located along the centerline of plate 42, it can be formed closer to one 
edge, if desired. While plate 42 can be manufactured in any desired 
manner, it is preferably formed from aluminum by extrusion. Channel 44 has 
a circular cross-section with an inside diameter "X". It is necessary to 
position a thin walled tubular member 46 within channel 44. While tubular 
member 46 may be made from any material, copper and aluminum are 
preferred. Very tight, continuous contact between tubular member 46 and 
channel 44 is very important for optimum heat transfer from plate 42 to 
tubular member 46. Thus outside diameter "X" of tubular member 46 should 
be the same or slightly greater than the inside diameter "X" of channel 
44. Clearly, the tubular member could not be forced into channel 44, 
either lengthwise or through the side opening of channel 44 without damage 
to thin walled tubular member 46 and/or the edges of channel 44. We have 
found, however, that this assembly step may be easily performed by the 
apparatus shown in FIG. 1, as discussed in detail below. The key is the 
ability of this apparatus to restrain movement along the edges of plate 42 
in the direction indicated by arrows 48 while moving the central portion 
of plate 42 with channel 44 by a force applied approximately at arrow 50 
to move the central portion of plate 42 from the position shown in solid 
lines in FIG. 2A to that shown in broken lines. Such movement increases 
the inside diameter "X" of channel 44 sufficiently to permit tubular 
member 46 to be easily slid into place from one end of plate 42. As 
described below, this function of uniformly flexing plate 42 along its 
entire length is performed by the apparatus of this invention in an 
efficient and expeditious manner. 
While fixtures 20 can be manufactured in any desired manner, such as by 
machining the fixtures from solid bar stock, the assemblies illustrated in 
FIG. 3 are preferred for simplicity and accuracy of manufacture and 
effectiveness in performance. FIG. 3 is an end view of the apparatus of 
FIG. 1, with end caps 26 removed and a typical solar plate 42 positioned 
for work. Basically, fixtures 20 each includes a channel member 52 resting 
on one leg with the opening toward tube 16. A spacer 54 is fastened to the 
inside base of the channel. Preferably, spacers 54 are rectangular 
cross-section tubing, welded in place. The thickness of spacers 54 
determines the angle of the shallow V-shaped concavity. If plate 42 were 
more nearly planar, the depth of the concavity could be decreased, while 
if the edges of plate 42 were at a greater angle, a thinner spacer 54 and 
a deeper concavity might be desireable. A pair of die bars 56 are secured, 
such as by welding, to the edges of channel 52 and the surface of spacers 
54. While die bars 56 could be installed so as to meet at the center, it 
is preferred that a narrow gap be maintained as shown, to accept a guide 
tab as described below. 
In most cases, when tubular member 46 is inserted into channel 44, it is 
necessary that a small portion of tube 46 extend beyond plate 42 for 
connection to a fluid manifold. Where the length of plate 42 is less than 
the overall length of the forming device, it is difficult to insert 
tubular member 46 to the exact distance desired. The tool 60 shown in 
FIGS. 5 and 6 assures correct positioning of tubular member 46. Tool 60 
consists of an end plate 62 with a rod 64 extending perpindicular to the 
plate and, in some cases, a tab 66 near the end of rod 64. In use, a plate 
42 is inserted into the apparatus as shown in FIG. 3, with one end near 
the end of the apparatus shown to the right in FIG. 1. A tool 60 is 
inserted into the left end of the apparatus (as seen in FIG. 1). The 
length of rod 64 is selected so that the end of the rod abuts the end of 
plate 42 within the apparatus. Rod 64 lies along the concave V-shape as 
seen in FIGS. 3 and 5. End plate 62 conforms in dimensions substantially 
to those of an end cap 26, so that when the lower edge of end plate 62 
rests on table top 20, rod 64 will be aligned with the gap between die 
bars 56. While short rods 64 need no support other than end plate 62, 
longer rods are kept in place much more easily by the addition of tab 66 
which rides in the gap between die bars 56 as seen in FIG. 3. Without tab 
66 the end of a long rod 66 may sag sufficiently to permit a tubular 
member 46 to be pushed too far into channel 44. 
FIG. 7 shows the apparatus in operation. Knob 34 has been moved to operate 
the air valve to admit air into tube 16, causing it to expand. The edges 
of plate 42 are restrained from movement by die bars 56. The area of plate 
42 adjacent to channel 44 is not restrained so that the pressure of tube 
16 flexes plate 42 to increase the channel diameter. A tubular member 46 
can then be inserted until it bears against the end of rod 64. In this 
example shown in FIG. 7, rod 64 is relatively short and does not have a 
tab 66. Air is then exhausted from tube 16, allowing the elasticity of 
plate 42 to return channel 44 to its original diameter, now tightly 
clamped around tubular member 46, as seen in FIG. 8. The extension of 
tubular member 46 beyond plate 42 was accurately set by rod 64 when the 
tubular member 46 was inserted into channel 44. 
While for purposes of the above description of a preferred embodiment the 
cross-sections of channel 44 and tubular member 46 are referred to as 
circular (said circular cross-sections being preferred), other 
cross-sectional shapes may be used if desired, so long as the outer shape 
and dimensions of tubular member 46 conform to the inner shape and 
dimensions of channel 44. 
Although certain specific materials, components and arrangements were 
detailed in the above description of preferred embodiments, these may be 
varied within the scope of this disclosure, where suitable. For example, 
while a preferred embodiment in which two tubes mounted on both sides of a 
wall cooperate with two concave fixtures, a single set of tube and shaping 
fixture may be used if desired. 
Other applications, variations and ramifications of this invention will 
occur to those skilled in the art upon reading this disclosure. These are 
intended to be included within the scope of this invention, as defined in 
the appended claims.