Abstract:
A soldering heater cartridge with replaceable tips and a soldering iron for use therewith is constructed of a tip heater cartridge with an elongated cartridge body that has a tubular body member, electrical connectors at a first end of the tubular body member for plug-in connection with an electrical connector assembly of a soldering iron handpiece, a soldering tip for mounting on the cartridge body and a heater mounted within the cartridge body and electrically connected to the electrical connectors. The tip end part is located at a second end of the cartridge body and the heater is located within the tip end part, the soldering tip being replaceably mountable over the tip end part in heat exchange contact with it.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to soldering irons and soldering stations used in modern electronic production, rework and repair applications which are temperature controlled, and specifically relates more to production type soldering stations which feature a heater which is either replaceable or integral with the soldering handpiece and which utilizes separately replaceable tips which wear during normal use. The invention also relates to such soldering irons and soldering stations which use a combined tip/heater cartridge, and in which the entire tip/heater cartridge is changed when the tip wears out. 
     2. Description of Related Art 
     The products the first type mentioned above are produced by WELLER®, PACE®, ANTEX®, ERSA® and HAKKO®; see also, commonly owned, co-pending U.S. patent application Ser. No. 09/973,952. The products of the second type mentioned above include the tip/heater cartridge product of METCAL INCORPORATED, or a combined heater/thermocouple arrangement such as that found in U.S. Pat. No. 5,043,560 (Masreliez) and in the Model 941 soldering station of the Hakko Corporation (Miyazaki U.S. Pat. No. 6,054,678); see also, U.S. Pat. No. 4,839,501 of METCAL® and commonly owned, co-pending U.S. patent application Ser. Nos. 09/972,194 and 10/046,545. Compared with traditional soldering stations, tip/heater cartridge stations generally offer significantly improved heat delivery and responsiveness as well as a slim, lightweight and often cooler handpiece which many operators prefer. 
     Conventional soldering stations for modern, high-reliability electronic production, rework and repair applications (hereinafter, “soldering stations” shall also include “soldering irons”) have become the generally accepted norm due to their ability to maintain a safe, appropriate, user-selected tip operating temperature for the particular application at hand. Such traditional soldering stations generally feature a soldering iron handpiece which consists of a handle and a closed-loop temperature controlled heater onto which a replaceable soldering tip is attached through various means, examples of which include the products made by WELLER®, PACE® ANTEX®, ERSA® and HAKKO®. These tip attachment means include a variety of configurations which are well known to the art. One configuration is a hollow heater into which tips are installed and fastened with set screws. Another configuration includes a thin cylindrical heater over which a hollow tip is installed and held in place by a shroud which fits over a shoulder on the tip and is fastened to the handpiece with a nut. Still another tip attachment means includes a thin, cylindrical heater with a stainless steel shroud over which a hollow tip is installed and held fast by some spring means which includes a separate spring ring, a spit in the open end of the tip that fits over the shroud, a combination of these two features or an independent coil spring with one end attached to the handpiece and the other end formed in a small hook shape which when stretched slightly engages a hole in the side of the tip thereby holding it in place. 
     Most of these conventional soldering stations offer adequate thermal performance, operator comfort and ease of use for older electronic assemblies. In addition, they provide relatively economical operation in that the replaceable tips are generally in the $4.00 to $8.00 dollar range in cost and the heaters need replacement only occasionally. However, when their heaters need replacement, they can be quite costly upwards of $75 dollars each or more and/or can be very time consuming or difficult to replace, often requiring soldering or desoldering. However, some soldering irons feature easily replaceable heaters, such as the PACE PS-80/90 handpieces; but, the cost of heater replacement is still relatively high. Furthermore, with other conventional soldering irons, the heater is not replaceable at all (ANTEX and WELLER SILVER SERIES), so that the entire handpiece must be replaced, sometimes costing upwards of $125 dollars or more. 
     In recent years, many of the latest electronic assembly and rework applications have very high thermal mass joints on circuit boards with ground planes, or incorporate a very high degree of miniaturization where access to the electronic components and joints is quite limited. In these situations, conventional soldering irons may not provide sufficient heating capability or responsiveness or their relatively bulky heaters and tips do not allow the operator to easily view and solder smaller joints in hard to reach, tight places. In very high through-put electronic production environments, operator comfort, ease of use and efficiency can also suffer due to the relatively large physical dimensions of the handpiece itself, the relatively long distance between the grip portion of the handpiece and the working end of the soldering tip, and the build-up of heat in the handle due to the proximity of the heater to the grip. In addition, many of these soldering stations feature operator selected temperature control which, in some manufacturing environments with relatively unskilled operators, has become a less desirable feature as the supervisor prefers that the operator solder at one specified temperature. 
     For all the reasons, tip/heater cartridge stations, with their attendant advantages outlined above have become quite popular, particularly in the large contract manufacturing environments. However, because tip life (either conventional tips or tip/heater cartridges) is limited by several factors, such as tip operating temperature, iron plating thickness, solder flux composition and other factors, these tips must be replaced quite frequently, sometimes as often as once per day depending on usage. While conventional soldering tips are relatively inexpensive as discussed above, replacing of tip/heater cartridges can be quite expensive as these cost anywhere from upwards of $12 to $24 dollars each or more. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to create an easily replaceable tip end which attaches to the end of an easily replaceable heater cartridge such that only the tip end needs to be replaced at a fraction of the cost of replacing a traditional tip/heater cartridge while offering all or most of the advantages of a tip/heater cartridge. 
     It is another primary object of the present invention to create a soldering iron with an inexpensive, easily replaceable heater cartridge which uses inexpensive, easily replaceable tips. 
     It is yet another primary object of the present invention to provide an easily replaceable, inexpensive heater cartridge which offers improved heat transfer and responsiveness over conventional soldering irons (such as by providing the heater bobbin with a silvered end portion on which the tip end seats). 
     A further object of the present invention is to provide an easily replaceable, inexpensive heater cartridge and tip combination which offers improved physical dimensions (such as a short tip-to grip for better control, and a thin heater and tip for easy access and viewing in tight spaces) in addition to improved heat transfer and responsiveness relative to conventional soldering irons. 
     It is still another object of the present invention to provide an easily replaceable, inexpensive heater cartridge and tip combination which offers improved comfort to the operator by keeping the heat of the handpiece well away from the grip portion thereof. 
     These and other objects are achieved by the provision of a heater cartridge composed of a stainless steel tube, a ceramic-potted heater assembly contained within a cylinder closed at one end which is either squared off or tapered and made from a high thermal conductivity material, such as silver, and wherein the heating element is connected to a dissimilar metal which forms a thermocouple, also containing cold lead wires of greater cross-sectional area than the heating element, an end insert which supports and fixes electrical contacts, and wire insulation. The heater cartridge accommodates a replaceable tip which slips over the closed end and is retained, e.g., by a spring, clip, internal thread mating to an external thread on the heater, a pin on the heater and track on the tip, interference fit between tip and heater, or other means. 
     The heater cartridge with slip-on tip offers an economic advantage to its users. The user can have several heater cartridges and slip-on tips so that when a new or alternate tip is required, the heater cartridge with slip-on tip is removed and a cool heater cartridge (with a replacement slip-on tip already attached) is installed into to the iron. The user need not inventory a large number of tip heater cartridges, but instead needs only a few heater cartridges at each station. Inexpensive slip-on tips can be inventoried at substantially lower cost and require less storage space than their costly tip heater cartridge counterparts. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a preferred embodiment soldering iron with a heater cartridge in accordance with the present invention with the soldering tip removed; 
     FIG. 2 is a cross-sectional view of the front end portion of the FIG. 1 heater cartridge; 
     FIG. 3 is a side view of a soldering tip for used with the FIG. 1 heater cartridge; 
     FIG. 4 is a plan view of a spring clip for use with the FIG. 3 soldering tip; 
     FIGS. 5-7 each show a respective alternative arrangement for mounting and retaining of a soldering tip on the end of a heater cartridge; 
     FIG. 8 is a side view of another alternative solder tip arrangement for mounting and retaining of a soldering tip on the end of a heater cartridge; and 
     FIG. 9 a cross-section taken along line  9 — 9  in FIG. 8 with an illustration of a spring clip being slid thereon; 
     FIG. 10 is a side view of the front end portion of an alternative heater cartridge; and 
     FIG. 11 shows the FIG. 8 soldering tip mounted on the FIG. 10 heater cartridge using a spring clamp. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The soldering iron  1  in accordance with the present invention has a handpiece  3  and a heater cartridge  4 . The handpiece  3  has an elongated hollow body with an inner passage that is open at an outer end of the passage for receiving the heater cartridge  4 . An electrical connector assembly  7  is mounted in an inner end of the passage, being inserted from the opposite direction as the cartridge  4 , and then being held in place by an end cap  9  that is screwed onto threads (not shown) of the handpiece  3  and through which an electric power cord (not shown) extends. This constructional feature allows the connector assembly  7  to be removed for maintenance or repair. 
     The electrical connector assembly  7  may comprise leaf spring connectors  21   a ,  21   b ,  21   c , which are mounted in a receptacle body  23  which has slots for reception thereof. When the cartridge  4  is plugged into the handpiece  3 , the leaf spring connectors  21   a ,  21   b , slide onto the plate-shaped electrical connectors  18  to form an electrical connection with an electrical heater  12  (FIG. 2) located in a tip end part  14  that is mounted at the front end of the tubular body member  10  of the cartridge  4 . The leaf spring connector  21   c  slides onto the tubular body member  10  (which is preferably made of stainless steel) of cartridge  4  to provide a grounding interface connection therewith, as the inner end of the heater cartridge  4  is moved into the tubular portion of the receptacle body  23 . While a bent tab of one of the plate-shaped electrical connectors  18  is shown attached to an end of one of the leads of the cartridge heater in FIG. 2, it should be appreciated that this connection is formed after the leads are passed through a cartridge end cap  22  which has surfaces and notches for receiving and supporting plate-shaped connectors  18  and their bent tabs. 
     An O-ring  27  is mounted at the front end of the receptacle body  23  and is held thereagainst by a formation on an inner surface of the handpiece  3 . The O-ring  27  forms a sealed interface with respect to the tubular body member  10  of the heater cartridge  4  when it is fully inserted. As a result, fumes produced during soldering processes performed with the soldering iron cannot flow into the connector assembly  7  where they could corrode the connectors. Additionally, the O-ring also serves to assist in retaining the cartridge within the handle and provides additional lateral support to the cartridge  4 . Additionally, in the illustrated embodiment, a sleeve  16  is mounted on the exterior of the cartridge  10  body for orienting and supporting the cartridge  4  relative to the soldering iron handpiece  3  by engagement thereof with inner surface areas of said passage. 
     The construction of the soldering iron  1  and cartridge  4 , and the manner in which the cartridge  4  is replaceably mounted in the handpiece  3 , as described so far, corresponds to that of commonly owned, co-pending U.S. patent application Ser. No. 09/972,194, which is hereby incorporated by reference. However, the nature of the cartridge body, construction of the heating element, electrical connectors, handpiece and manner of mounting of the cartridge in the handpiece, by themselves, form no part of this invention and can be of any type and arrangement known in the art; see, e.g., U.S. Pat. Nos. 4,839,501 and 6,054,678. 
     On the other hand, whereas the tip end part  14  constitutes the soldering tip in the soldering irons of the prior art, such is not the case in accordance with the present invention. Instead, the tip end part  14  in accordance with the present invention is designed to give the heater cartridge a replaceable tip capacity. Preferably, the tip end part  14  is formed of a material of high thermal conductivity in comparison to a material of which the stainless steel tubular body member  10  of the cartridge body is formed, the material of high thermal conductivity preferably is silver, but the material of high thermal conductivity can be copper or other materials of comparable thermal conductivity. Furthermore, while the tip end part  14  is preferably a separate element fixedly joined to the tubular body member  10  of the cartridge body  4 , it can be formed as an integral part thereof. 
     With reference to FIG. 3, the soldering tip  20  has an expandable open end portion  20   a  for mounting over the tip end part  14 . The expandability of the open end portion  20   a  of the soldering tip  20  is produced by a plurality axial slots  21  formed in the peripheral wall  20   b  of the open end portion  20   a , only one of which is shown. A securing member in the form of a C-shaped ring clamp  22  (FIG. 4) is seatable on the expandable end portion  20   a  for restraining expansion thereof, thereby releasably holding the soldering tip  20  on the tip end part  14 . Preferably, as shown, the peripheral wall  20   b  has a circumferentially extending seating recess  20   c  formed therein for holding the C-shaped ring clamp  22 . However, a snap-ring spring clamp or other securement means could be used instead of the C-shaped ring clamp  22 . Alternatively, a separate securing means can be omitted, e.g., if the “legs” formed by the slits  21  are shaped to be placed under a radial pre-stress when mounted on the cartridge  4  by being outwardly deflected in such a mounted state. 
     With reference to the C-shaped ring clamp  22  of FIG. 4, instead having a circular cross section, clamp  22  can have flat, band-shaped cross section. In such a case, the seating recess  20   c  can be omitted. Additionally, because of its proximity to the heater, the claim  22  is preferably made of a high temperature resistant material, such as Inconel®. 
     In the embodiment of FIGS. 1 &amp; 2, the peripheral wall of the tip end part  14  has the same outer diameter as the outer diameter of the tubular body member  10 , except where it is reduced for insertion into the tubular body member  10 . The soldering tip  20  has a cylindrical receiving chamber  20   d  with a conic bottom wall, and the tip end part has a cylindrical peripheral wall and conic end face matched to the size and shape of the receiving chamber for providing a removable slip-on fit with optimized heat transfer communication between the soldering tip and tip end part. 
     In contrast, soldering tip  20  has an inner diameter in the embodiments of FIGS. 5 &amp; 6, the peripheral wall of the soldering tip  20 ′,  20 ″ have substantially the same outer diameter as the outer diameter of the tubular body member  10  and seat on a portion of a tip end part  14 ′,  14 ″ that has an outer diameter that is reduced relative to outer diameter of the tubular body member  10  by the thickness of the peripheral wall surrounding the receiving chamber. In the FIG. 5 embodiment, to releaseably hold the tip  20 ′ on the tip end part  14 ′, a ring  25  is mounted in an annular seat recess of the peripheral wall of the receiving chamber. The ring  25  has an inner diameter that is smaller than the outer diameter of portion of the tip end part  14 ′ on which mounts so that, insertion of the tip end part  14 ′ into the receiving chamber stretches the ring, which can be a C-shaped ring clamp similar to clamp  22  or an annular coil spring or the like, radially outwardly to an extent creating sufficient spring force to hold the tip in place, but still allowing removal of the tip  20 ′. 
     In the case of the FIG. 6 embodiment, a compressible ring, detent member  28  is located in an annular seat recess  14 ″ a surrounding the reduced diameter portion of the tip end part  10 ″ on which tip  20 ″ is mounted. The soldering tip  20 ″ has an annular seating groove  20 ″ c  which communicates with a pair of radial tool holes  20 ″ e  that are located 180° apart. As the soldering tip  20 ″ is slid onto the tip end part, the ring detent member  28  is compressed into the seat recess  14 ″ a . Once the tip is properly seated, the seating groove  20 ″ c  is axially aligned with the recess  14 ″ a  and the ring detent member  28  expands radially outward into the seating groove  20 ″ c , holding the soldering tip  20 ″ in place. To remove the soldering tip  20 ″, ends of a forceps-like tool T is inserted into the tool holes  20 ″ e  and is used to compress the ring detent member  28  sufficiently to become disengaged from the seating groove and to pull the soldering tip  20 ″ forward. 
     In FIG. 7, yet another means for releaseably mounting the soldering tip on the tip end part is shown. In this case, the soldering tip  20 ′″ has the female slot part  29  of a bayonet type lock and the tip end part carries the male pin part  20  of the bayonet type lock. 
     FIGS. 8 &amp; 9 show a soldering tip  20 ″″ that is designed for use with either a hose type clamp or a spring clip. In this embodiment, open end  20 ″″ a  has a noncircular transverse cross-sectional shape as is shown in FIG.  9 . As can be seen, a pair of lobes  35  are formed 180° apart and have slots  35   a  formed therein. A spring clip  40  can be slid in the direction of the arrow in FIG. 9, through slots  35  onto tip end part so as to hold the tip  20 ″″ in place. Alternatively, a hose type clamp can be expanded and slid axially over the tip and then released to engage tip end part via the slots  35 ; see, FIG.  11 . 
     As shown in FIG. 10, the tip end part  14 ″″ can have a rounded end instead of the drill point shape shown in FIGS. 1 &amp; 2, which is particularly useful when the tip end part is formed of a silver casting or a sintered silver body. Furthermore, tip end part  14 ″″ can have a maximum outer diameter that is smaller than an outer diameter of said tubular body member and can be force-fit mounted in an open end of the body member  10 . As represented in broken lines in FIG. 8, for use with such a tip end part  14 ″″, the receiving chamber  20 ″″ d  of the soldering tip is given a rounded shape matched to it. 
     As should be apparent from the foregoing, numerous different arrangements can be utilized to implement the inventive concept, so that the present invention is not intended to be limited to only the specific embodiments shown, but rather is intended to include all variations and modifications encompassed by the scope of the appended claims. For example, the soldering tip could have an internal threading and the tip end part a matching external threading instead of using clips or detents to hold the soldering tip on the tip end part of the cartridge.