High Speed Desoldering Tool

In the drawings:

FIG. 1 is a side elevational view of a tool in accordance with the present invention partially broken away to reveal internal construction;

FIG. 2 is an exploded elevational view showing removal of the solder collector tube;

FIG. 3 is an enlarged fragmentary sectional view through a portion of the structure of FIG. 1;

FIG. 4 is an enlarged sectional view through the tip showing how the lead wire of a component of a circuit board assists in cleaning the tip.

A number of the components of the present device are similar in structure and function to those of U.S. Pat. No. 4,318,504 and the same reference numerals are used to designate corresponding parts. Thus, the present invention may be used on the bench or in the field to remove solder from a joint such as on a printed circuit board 61 (hereinafter described). The device is hand-held, and, for convenience, is preferably generally similar to the shape of a pistol. At the distal end of the tool is a hollow conical tip 11, hereinafter described in detail, disposed generally at about a 45.degree. angle to the normal holding position of the tool, an angle which is most convenient for removing solder from the work which may be either flat on the bench or tilted 45.degree. from the horizontal. Tip 11 is threaded into tip holder 12 and leading from the tip holder 12 is a suction tube 13 which is short, of small diameter and preferably of a material to which molten solder does not adhere such as stainless steel. Beryllium copper plated with electroless nickel is a suitable material for tip 11 and holder 12 for long life. The upper end of tip holder 12 is fixed to heater element 14 and the proximal end of heater element 14 is fitted into the forward end of the tool casing 18 by means of a nose piece 17, or other convenient means. Casing 18 is hollow and generally of a pistol shape having a conveniently shaped handle 19.

Inward of suction tube 13 is a large diameter, thin-walled solder collector tube 21 of stainless steel or other suitable material. Between the proximal end of tube 21 and casing 18 is a connecting rear seal 22. Communicating with the upper end of rear seal 22 is a nylon tube duct 24 through which a vacuum is drawn from the tip 11, suction tube 13, collector tube 21 and rear seal 22.

Located in handle 19 is a solenoid 26 having a plunger 27 biased away from the solenoid 26 by return spring 28. Smooth bore cylinder 29 having a head 31 extends beyond solendoid 26. Piston 33, which is described in detail in U.S. Pat. No. 4,318,504, is fixed to plunger 27. Duct 24 connects with head 31.

On the front of handle 19 and extending through an aperture therein is a trigger 46, pivotted at its upper end by pivot 47 to casing 18. Inside trigger 46 is a snap action switch 48 which has a switch actuator 49 contacted by trigger 46 when it is squeezed inwardly, thereby closing the switch 48. The electrical wiring of the tool includes a printed circuit board 51 received in the upper end of housing 18.

A number of significant improvements in the construction of the tool will next be described.

Directing attention now to structure of the tip 11, the exterior thereof tapers inwardly-downwardly and the outer end is formed with a hole 56 which communicates with a cylindrical larger diameter bore 57 in which rotates a twisted, flat helical piece of spring stainless steel 58. Helix 57 is slightly longer than the bore 56 so that the upper end 64 thereof extends out through the proximal end of tip 11. When suction occurs, the helix turns allowing solder to pass by it without collecting at the bottom of the tip. However, if it is necessary from time to time to clean the tip, the tip 11 may be removed and the operator may turn the exposed ends 64 of the helix with pliers, or other tool, thereby scraping any obstruction from the interior of the tip.

In order to clean the tip holder 12, a clean-out tube 66 which may generally be in alignment with the suction tube 13 is normally closed off with a set screw 67. By removing the set screw 67, a cleaning implement may be inserted through the tube 66 and into the tip holder 12.

As shown in FIG. 4, a typical use for the tool of the present invention is in removing solder holding component 62 to a circuit board 61. Component 62 has a lead 63 secured to board 61 by solder. The end of the lead penetrates the hole 56, assisting in cleaning it.

Directing attention now to features of the collector tube 21, fixed to the right-hand end of the suction tube 13 (as viewed in FIGS. 1 and 2) is a forward or distal steel 71 having a spherical surface which seals against the chamfer 72 in the forward end of tube 21.

Rear seal 22 is an injected molded part made of a durable plastic such as Dupont Hytrell. It has an enlarged collar 76 formed with a taper 77 into which the proximal end of tube 21 seats. Spring 81 surrounding duct 24 bears against the rear seal 22, biasing it toward the left as viewed in FIGS. 1-3 and holding the tube 21 in place. By gripping the rear seal 22 and forcing it toward the right against the action of spring 81 (i.e., moving it from the operative or dot-and-dash line position of FIG. 2 to the solid line position) the tube 21 is released from the collar 76 and may be removed for cleaning and replacement of the filter. The proximal end of rear seal 22 is formed with a reduced diameter portion 78 which engages the exterior of the duct 24. An outward flare 79 of tube 24 prevents the duct 24 from falling out of place.

Within the proximal end of collector tube 21 is filter 86 of sponge plastic, or other suitable material. The distal face of the filter 86 has affixed thereto a disc 87 of thin neoprene rubber. Solder pellets drawn into the collector tube 21 by vacuum may contact the disc 87, thereby preventing damage to the filter 86.

Filter 86 allows air to pass through by flexing whenever a vacuum pulse is generated by solenoid 26. The contaminated air goes around the disc 87 and through the filter 86 which removes solder fumes, fluxes, oxidants and whatever dirt is carried in. Thus filter 86 protects the inner working parts of the vacuum pump. The disc 87 bonded to the foam filter 86 becomes a "crash" plate for the incoming solder. Since the solder is usually in the form of a spray, it solidifies and falls down to the walls of the cylinder 21 and thus does not stick to the filter.

Directing attention to FIG. 3, the flexing action of the disc 87 is shown. When the vacuum stops, the filter 86 acts as a spring, forcing the disc 87 forward to a position perpendicular to the axis of cylinder 21. Thus, an airpath is always open until such time as the collector cylinder 21 is full of solder.