Abstract:
A method of forming a solder joint includes the steps of providing a heat shield member formed as an arcuate preferably metallic shell attached to a spring-clamp by means of an obedient shaft; attaching the spring clamp to a structure adjacent the solder joint; moving the heat shield member by bending the obedient shaft so that the heat shield member is positioned in a location spaced-apart from the solder joint with the concave surface of the heat shield member facing the solder joint; and applying heat from a torch to the solder joint from the side opposite the heat shield so that the heat shield reflects the heat back onto the solder joint.

Description:
CLAIM OF PRIORITY 
     This is application claims priority of pending U.S. patent application Ser. No. 13/474,392 filed on May 17, 2012, which claims priority of U.S. Provisional Patent Application 61/490,044 filed on May 25, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to hand tools, and in particular to hand tools for use by plumbers. 
     In the plumbing trade, it is common to sweat together joints in copper pipe and other metal plumbing fittings using an open-flame torch together with an appropriate solder or brazing alloy. Often, especially when plumbing repairs are being performed, as opposed to new construction, the joint being assembled is in close proximity to wall studs, insulation, drywall, electrical wiring, or other building materials that may be damaged by the open-flame torch. Accordingly, it is desirable to have some means of protecting the materials adjacent the joint being assembled. 
     Flexible mats formed of a heat resistant fiberglass material are commonly employed to protect the area around the solder joint, but these mats are often difficult to place, especially when working overhead as the mat tends to drop onto the joint itself. The fiberglass mats also wear out quickly, requiring frequent replacement. Heat resistant gels are also commonly used to prevent heat damage to protect the area surrounding the joint during soldering. Heat resistant gels, however, are expensive and cannot be applied to extremely porous surfaces such as cellulose insulation. It is known in the art to form crude heat shields from soft drink cans, however, these heat shields are difficult to position properly. Accordingly, what is needed is a reusable, durable heat shield device that can be easily positioned to protect the area surrounding the joint during soldering regardless of the orientation of the joint and the surrounding building materials. 
     SUMMARY OF THE INVENTION 
     The present invention comprises a reusable, durable heat shield for use in protecting the area surrounding a solder joint during the soldering process and method of using the heat shield. In the illustrative embodiment of the invention, the heat shield comprises an arcuate metallic shell attached to a spring-clamp by means of an obedient shaft which enables the heat shield to be moved to any position relative to the spring-clamp so that the shield can be placed behind the joint being soldered. The arcuate shell is preferably formed from a material having a high infrared reflectivity and low affinity for tin-lead and lead-free soldering alloys. The obedient shaft is preferably formed from helically-wound steel spring outer sheath surrounding a ductile copper wire core. The spring steel outer sheath prevents the ductile copper wire core from being bent at too sharp of a radius (which would cause the ductile core to work-harden and fracture) while at the same time protecting the ductile copper wire core from the open-flame torch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawing figures in which like references designate like elements and, in which: 
         FIG. 1  is an exploded, perspective view of a plumber&#39;s heat shield incorporating features of the present invention; 
         FIG. 2  is a front perspective view of the plumber&#39;s heat shield of  FIG. 1 ; 
         FIG. 3  is a rear perspective view of the plumber&#39;s heat shield of  FIG. 1 ; 
         FIG. 4  is a perspective view of the plumber&#39;s heat shield of  FIG. 1  in position to protect the area surrounding a solder joint during the soldering operation; 
         FIG. 5  is a perspective view of an alternative embodiment of an end fitting for attaching the obedient shaft to the heat shield; and 
         FIG. 6  is a perspective view of another alternative embodiment of an end fitting for attaching the obedient shaft to the heat shield. 
     
    
    
     DETAILED DESCRIPTION 
     The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the detailed description and in the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and detailed description are not intended to limit the invention to the particular form disclosed, but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention. 
     With reference to  FIGS. 1-3 , plumber&#39;s heat shield  10  comprises an arcuate shell  12  which is attached to a spring clamp  14  by means of obedient shaft  16 . Arcuate shell  12  preferably comprises a cylindrical sector approximately 4 inches long, having a radius of curvature “R” of from 1 to 4 inches and preferably about 2 inches and an included angle of between 30 degrees and 180 degrees, preferably about 90 degrees (¼ circle). 
     Arcuate shell  12  is preferably formed of a metallic material having a low affinity for conventional tin-lead solder and lead-free solders, which consist typically of tin, copper, bismuth, and silver. At the same time arcuate shell  12  has a high reflectivity in the infrared range of the electromagnetic spectrum. Steel has low affinity for solder, but has poor infrared reflectivity. As used herein, a surface has high infrared reflectivity if its reflectivity is better than 70% in the infrared range of the electromagnetic spectrum. Silver, gold and copper all have good (high) reflectivity in the infrared range of the electromagnetic spectrum (better than 90% if polished to mirror finish), however, all have high affinity for tin-lead and lead-free solders. Consequently, any solder that splattered onto the heat shield from the joint being assembled would be difficult to remove. Silver and gold are also too expensive to be of practical use. Aluminum that is polished to a mirror finish has the highest reflectance of any metal in the 3,000-10,000 nm (far IR) regions and is significantly less expensive than silver, gold or copper. Aluminum also has significantly lower thermal capacity and therefore cools faster if accidentally heated. Accordingly, in the illustrative embodiment arcuate shell  12  is made from ⅛ inch thick aluminum with the concave surface  18  being polished to a high gloss (63 micro-inches Ra or smoother) or, preferably polished to a mirror finish (8 micro-inches Ra or smoother). Nonmetallic shells, such as thermoset plastics and high temperature thermoplastics, may also be used, provided the concave surface is coated with a high gloss or mirror finished aluminum metallization. 
     Obedient shaft  16  comprises a helically wound steel spring outer sheath  20  having an outer diameter of less than about ⅜ of an inch, preferably about ¼ inch O.D. Preferably outer sheath  20  is between 12-24 inches long, preferably about 18 inches long and is wound from conventional steel spring wire having a wire diameter of 0.04-0.08 inch in diameter. The coils of outer sheath  20  are preferably close-packed so that outer sheath can bend or elongate, but cannot be compressed. Obedient shaft  16  further comprises a ductile core  22  ( FIG. 6 ), disposed inside outer sheath  20 . Ductile core  22  can be formed of any malleable material such as steel or aluminum wire but in the illustrative embodiment comprises solid 12-gauge soft (annealed) copper wire which is just small enough in diameter to be slid inside outer sheath  20  (e.g. with a diameteral clearance of 0.009 to 0.089 inch). Using copper for ductile core  22  has the advantage over steel or aluminum in that it has a lower modulus of elasticity and therefore is more malleable and, although copper does work harden if bent repeatedly, copper can be annealed simply by heating. Obedient shaft  16  is capable of supporting a load of at least 1 ounce cantilevered 18 inches horizontally outward along the obedient shaft without moving. 
     It is important that obedient shaft  16  be made from a metallic outer sheath  20  with a ductile core  22  rather than with conventional gooseneck tubing. Although gooseneck tubing is flexible, what the inventor of the present invention discovered was that conventional gooseneck tubing, which relies on interference between the helical windings of each adjacent layer to give the gooseneck tubing its obedience, quickly lost its elastic strength if the flame from the open-flame torch came in contact with the gooseneck tubing. Use of a helically wound steel spring outer sheath in combination with a ductile copper wire core enables the obedient shaft of the present invention to resist damage from the open-flame torch. 
     Obedient shaft  16  is attached to a shell  12  and spring clamp  14  by means of fasteners  24  which are assembled through lugs  26  and  28  swaged onto the ends of obedient shaft  16 . In the illustrative embodiment of  FIG. 1 , fasteners  24  comprise threaded carriage bolts  30  with corresponding nuts  32 , however, any suitable fastener such as rivets, screws, or adhesives may be used without departing from the scope of the invention. The fasteners  24  are assembled through one of a plurality of apertures  34 ,  36 ,  38  formed along the lower edge  37  of shell  12 . Apertures  34 ,  36 ,  38  permit the shell  12  to be positioned in different locations depending on the needs of the user. Apertures  34 ,  36 ,  38  are non-circular (preferably square) and are sized to accommodate fasteners  24  so as to provide an anti-rotation feature for maintaining the heat shield in a fixed orientation. Alternatively, a lug similar to lug  28  may be utilized at shell  12  to provide anti-rotation. Shell  12  is free of windows made of transparent or semi-transparent materials as are found in welding helmets and the like, and is free of holes or other apertures other than apertures  34 ,  36  and  38  located along edge  37 . 
     Spring-clamp  14  preferably comprises a commercially-available spring clamp such as Irwin Tools model 222702 having a jaw opening of approximately 2 inches and a handle length of approximately 6 inches. This enables spring-clamp  14  to firmly clamp the edge of standard nominal 2-inch wall studs and floor joists (e.g. 2×4&#39;s, 2×6&#39;s, 2×8&#39;s etc. which have an actual width of approximately 1½ inch). Obedient shaft  16  is attached so that it extends from the handle portion of spring clamp  14 , although other attachment locations such as the pivot of clamp  14  are within the scope of the invention. 
     As shown in  FIG. 4 , a solder joint  40 , which is made between two pieces of pipe  42  and  44  is frequently in close proximity to a wall stud  46 . Therefore, it is desirable to protect wall stud  46  from the flame  48  of torch  50 . This is accomplished using plumber&#39;s heat shield  10  by clamping spring-clamp  14  to an adjacent wall stud  52 . Arcuate shell  12  is then positioned by bending obedient shaft  16  as necessary so that the concave surface  18  is located behind the solder joint  40  and facing substantially toward flame  48 . Flame  48  is then applied to the front side  49  to heat the joint to a sufficient temperature for the solder to flow into the joint. Arcuate shell  12  protects wall stud  46  from the heat of flame  48  by reflecting the infrared energy back toward the joint  40 . Accordingly, not only does arcuate shell  12  protect wall stud  46 , but because the infrared energy is reflected back toward joint  40 , joint  40  is heated more quickly than would occur if arcuate shell  12  were not present. 
     The polished surface  18  of arcuate shell  12  also reflects visible light, so that shield  10  doubles as an inspection mirror to enable the plumber, working from the front side  49  of the joint, to see the reverse side  51  of the joint being assembled. Thus, not only does the present invention comprise a reusable, durable heat shield, it also saves energy that would otherwise be wasted heating the fiberglass or gel heat absorbing the compounds of the prior art, and it performs the function of the inspection mirror that the user would otherwise have to purchase separately. 
     Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the invention. For example, although in the illustrative embodiment of  FIGS. 1-4  obedient shaft  16  is attached by means of lugs  26  and  28 , other methods of attachment such as cable strap  56  ( FIG. 5 ) or pinch bolt  58  ( FIG. 6 ) or any other means of attachment are considered within the scope of the invention. Accordingly, it is intended that the invention should be limited only to the extent required by the appended claims and the rules and principles of applicable law. Additionally, as used herein, references to direction such as “up” or “down” are intend to be exemplary and are not considered as limiting the invention and, unless otherwise specifically defined, the terms “substantially” or “generally” when used with mathematical concepts or measurements mean within ±10 degrees of angle or within 10 percent of the measurement, whichever is greater.