Abstract:
The conventional rapper design is improved to provide longer service without maintenance and easier access at less cost when service is required by, among other things, redesign of the hammer assembly, hammer shaft and lever assemblies, and the hammer assembly housings. Design improvements include the provision of access panels on the housings, a guide and lock mechanism for removing and inserting the hammer assembly out of and into the hammer assembly housing, providing the hammer with a removal, and keyed engagements of hammer shaft assembly components.

Description:
FIELD OF THE INVENTION 
     This invention relates to the maintenance and efficient operation of equipment designed to transport or process hot, dust-laden gases. In one aspect, this invention relates to maintenance equipment designed to prevent or retard the deposit of sticky solids on the interior walls and internal components of the hot, dust-laden gas transport/process equipment while in another aspect, the invention relates to such maintenance equipment that impacts or causes a temporary deformation or vibration of the interior wall of the transport/process equipment. In yet another aspect, the invention relates to design improvements to such maintenance equipment. 
     BACKGROUND OF THE INVENTION 
     Hiltunen and Ikonen, U.S. Pat. No. 5,443,654 which is incorporated herein by reference, provide a reasonably good description of the problem of deposit buildup in equipment designed and operated for transporting and/or processing hot, dust-laden gases. Hiltunen and Ikonen teach this problem in the context of a gas cooler inlet duct, but this problem is common to most equipment through which hot, dust-laden gases pass. As here used, “dust-laden” includes gases containing molten or evaporated material. As such gases cool and condense, the dust components may, depending upon their composition, become sticky and adhere to one another and the internal walls and components of the equipment in which the gas is contained. These deposits can grow quickly and interfere with the safe and efficient operation of the gas transport/processing equipment. For example, these deposits can block gas flow and/or reduce the efficiency of heat transfer between the hot gas and the gas transport/processing equipment walls and internals, e.g., heat-exchange tubes. Moreover, depending upon the design and materials from which the transport/processing equipment is constructed, e.g., metal, ceramic, etc., removal of these deposits can be difficult or less than 100% effective if the deposits are allowed to accrete beyond a certain size. 
     Various methods are known for preventing or retarding deposit formation within hot, dust-laden gas transport and/or processing equipment, and these methods include increasing the gas volume and/or turbulence, various scrubbing techniques, and imparting a slight but frequent deformation to the walls and/or components of the equipment to which the sticky, cooled dust is likely to adhere. As noted by Hiltunen and Ikonen, these deposits tend to be brittle and subject to removal through mechanical deflection of the wall or structure upon which they are deposited. 
     Various methods are known for imparting a mechanical force to a surface to which a deposit may or has formed to either prevent or remove the deposit. Hiltunen and Ikonen teach one such method. Another is taught in FIGS. 1,  2 ,  4 ,  6 ,  8 ,  10  and  12  in which like numerals are employed to designate like parts throughout the Figures. Various items of equipment such as electrical connections, fittings and the like are omitted so as to simply the drawings. 
     FIG. 1 illustrates a “rapper”  100  attached by any conventional means, here by brace  101 , to the wall (shown in partial section) of a waste-heat boiler. The wall comprises exterior metal skin  102  and ceramic insulation  103 . The waste-heat boiler contains a plurality of heat-exchange tubes  104  (only one of which is shown) over and around which hot, dust-laden gases from any source, e.g., a metallurgical furnace, circulate. The tubes contain any suitable heat-exchange fluid (not shown) designed to capture by convection through the tube wall at least part of the latent heat of the gas. This transfer of heat from the gas to the heat-exchange fluid within the tube causes the gas to cool, and thus the dust components within the gas to condense and deposit on, among other places, the exterior walls of the tubes. Since the deposits of this example tend to be brittle in nature, their formation is impede or if formed, then easily removed, by imparting a mechanical force in the form of a small deflection or vibration to the wall of the heat-exchange tube. These tubes are often placed in contact with one another, and thus the vibration imparted to one tube is readily transferred to all of the other tubes to which it is in direct or indirect contact. 
     Rapper  100  imparts a mechanical force to heat-exchange tube  104  through the action of hammer  105  striking anvil  106 . Hammer  105  operates in a manner described below such that it periodically is retracted to a predetermined distance from the face of the anvil (e.g., 12-14 inches), and then released such that the face of the hammer impacts the face of the anvil with a predetermined amount of force. This force is transferred from the face of anvil  106  through disc spring  107  and anvil rod  108  to I-bar  109  and ultimately to tube  104  (and those tubes in direct or indirect contact with tube  104 ). I-bar  109  and anvil rod  108  are embedded in insulation  103  in such a manner that the majority of the mechanical force is transfer to tube  104  and not skin  102  or insulation  103 . 
     The principal components of the rapper are shown in FIG.  2 . The power to activate the hammer is provided by electric motor  201  which is operationally connected to gear reducer  202 . Shaft  203  of gear reducer  202  connects to and drives hammer assembly  204  by way of chain drive assembly  205  which consists of small chain sprocket  206 , chain  207  and large chain sprocket  208 . The chain drive assembly rotates hammer shaft assembly  210  and lever shaft assembly  209  (both shown in exploded format in FIG.  4 ), which in turn provide the action by which the hammer periodically is retracted and released to impact the anvil. Hammer assembly  204  is aligned within two piece hammer housing  211   a  and  211   b  such that the lever shaft assembly engages adjustable cam  212 . Lever shaft assembly  209  rotates in such a manner that once each rotation it engages cam riser  213 . As lever shaft assembly  209  passes over cam riser  213 , the hammer shaft assembly is disengaged from the chain drive assembly, and the hammer “falls” into the face of the anvil. Once the lever shaft assembly has cleared the cam riser, the hammer shaft assembly re-engages the chain drive assembly and the hammer is retracted and retained into its retracted position until the lever shaft assembly again engages the cam riser. 
     The amount of force delivered to the anvil is a function, in part, of the position of the cam riser on the cam. In this manner, the amount of force delivered to the anvil by the fall of the hammer can be controlled. Gear reducer  202  is housed in gear reducer housing  214  which is fastened by any suitable means to hammer housing  211   a.    
     FIG. 4 is an exploded view of lever shaft assembly  209  and hammer shaft assembly  210 . The lever shaft assembly comprises a lever shaft  401  carrying a middle bearing  402  and two bushings  403   a  and  404   b . Bushing  403   a  carries lever  404   a  and bushing  403   b  carries lever  404   b . Outside bearings  405   a  and  405   b  complete the complement of elements carried by lever shaft  401 . 
     Shaft  401  is aligned with cam  212  and cam riser  213  such that bearing  402  engages cam riser  213  once each rotation of hammer shaft assembly  210 , and bearings  405   a  and  405   b  engage hammer cams  407   a  and  407   b , respectively. Lever shaft assembly  209  is connected to hammer shaft assembly by two-piece hammer shaft casing  408   a  and  408   b . Casing  408   a  includes casing arm  409  designed to receive casing arm bushing  410  and casing arm shaft  411  to which levers  404   a  and  404   b  can attached in any conventional manner. In operation, the back of levers  404   a-b  engage stop pin  406  (FIG. 12) after the hammer falls into the face of the anvil. This engagement steadies (i.e., dampens the vibration of) the hammer and thus facilitates an easy re-engagement of the hammer shaft assembly with the chain drive assembly. Hammer shaft  412  is fitted to hammer  105  by way of hammer arms  413   a-b  each of which fare fastened to hammer  105  by any conventional means, e.g., welding. Each hammer arm contains an opening  414   a  and  414   b  respectively in alignment with one another and adapted to receive hammer shaft  412  with its complement of bushings  416   a-b ,  417   a-b  and  418 . Hammer shaft  412  is fitted within bushing  418  such that it extends out of both open ends of the bushing. Openings  414   a-b  are fitted with bushings  416   a-b , respectively. Bushing  418  with inserted hammer shaft  412  is inserted through bushings  416   a-b  such that it extends through both. Casing  408   a-b  engages bushing  418  about its central section in a compression fit, and bushings  417   a-b  are fitted between the respective inner surfaces of arms  413   a-b  and casing  408   a-b . Bushing  418  has neck  418   a  which is fitted into sprocket opening  230  and then welded or otherwise permanently fastened to sprocket  208 . Hammer arm block  419  contributes stability to the hammer assembly. 
     Spacer  415  also contributes stability to the hammer assembly. It is fitted over the end of bushing  418  that extends through opening  414   a  to occupy the space between the outer surface of arm  413   a  and the inner surface of housing  211   b  that is opposite arm  413   a . Sprocket  208  provides a similar stability function by occupying the space between the outer surface of arm  413   b  and the inner surface of housing  211   b  that is opposite arm  413   b . In both instances, this spacer and sprocket tend to restrict the movement of the hammer assembly relative to the hammer housing. 
     While the rapper described above performs reasonably well, often it proves difficult to service. Since rappers are in frequent use (a typical cycle for a rapper attached to a waste-heat boiler servicing a metallurgical furnace, e.g. a copper converter, is for the hammer to strike the anvil four or five times a minute for five minutes, remain at rest for fifteen minutes, and then repeat the cycle for as long as the furnace is in operation (which may be a year or more)), they require constant service. Rappers are often large, heavy pieces of equipment (the hammer assembly alone usually weighs more than one hundred pounds), and are often located in difficult to reach and/or service areas (e.g., high above ground, in tight corners, attached at odd angles, etc.). Moreover, on larger hot gas, dust-laden transport/processing equipment such as that associated with copper metallurgical furnaces, hundreds of rappers may be in service at one time, many located in close proximity to one another. Considerations such as these necessitate designs that favor relatively easy and inexpensive servicing. 
     SUMMARY OF THE INVENTION 
     The conventional rapper design is improved to provide longer service without maintenance and easier access at less cost when service is required. These improved results are through one or more of the following: 
     1. easier access to the hammer assembly and gear reducer without removal of their respective housings; 
     2. easier removal of the gear reducer housing and the hammer assembly housing when required; 
     3. easier removal of the hammer; 
     4. increased life of rapper components, and emphasizing inexpensive components for failure points (as opposed to expensive components); and 
     5. redesign of the hammer and various components of the lever and hammer shaft assemblies. 
     These and other features of the intention are described more filly below and by reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side, cut-away perspective of a rapper attached to the sidewall of an apparatus for transporting or processing a hot, dust-laden gas. The phantom-line drawing illustrates the hammer in a retracted position. 
     FIG. 2 is an exploded view showing the component parts of a conventional rapper. 
     FIG. 3 is an exploded view showing the component parts of a rapper of the invention. 
     FIG. 4 is an exploded view showing the lever and hammer shaft assemblies of a conventional rapper. 
     FIG. 5 is an exploded view showing the lever and hammer shaft assemblies of a rapper of the invention. 
     FIG. 6 shows the attachment means for securing the gear reducer housing to the hammer housing of a conventional rapper. 
     FIG. 7 shows the attachment means for securing the gear reducer housing to the hammer housing of a rapper of the invention. 
     FIG. 8 is FIG. 6 taken along line  8 — 8 . 
     FIG. 9 is FIG. 7 taken along line  9 — 9 . 
     FIG. 10 is a top perspective of the lever shaft assembly of a conventional rapper. 
     FIG. 11 is a top perspective of the lever shaft assembly of a rapper of the invention. 
     FIG. 12 is a side perspective of the lever engaging the stop pin of a conventional rapper. 
     FIG. 13 is a side perspective of the lever engaging the stop block of a rapper of the invention. 
     FIG. 14 is a side perspective showing the keyed engagement of the hammer shaft to the large chain sprocket of a rapper of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Rappers are in use when the hot, dust-laden gas transport or process equipment to which they are attached is in use. Since such equipment, e.g., a metallurgical furnace and its associated equipment (boilers, flues, etc.) are designed for long-term (e.g., months or years) continuous use, rappers are also designed for such use. For rappers attached to a waste heat boiler supporting a metallurgical smelting or converting furnace, the rappers may operate on a cycle of five to ten raps per minute for five minutes, ten minutes at rest, and then the cycle repeats. Such continuous use results in wear and deterioration of the various rapper components and as such, rappers require regular inspection and maintenance. 
     The design of conventional rappers as described in FIG. 2 does not lend itself to convenient and efficient maintenance. As shown in FIG. 2, the operating components of the rapper are sheltered in gear reducer housing  214  and hammer assembly housing  211   a  and  211   b . The design of the conventional rappers allow access to the interior and contents of these housings either by gear reducer housing access panel  215  or by the removal of either or both gear reducer housing  214  and/or hammer assembly housing  211   b . All of these maneuvers often prove inadequate. 
     With respect to access panel  215   a  it is located on the top of housing  214  and as such, it provides ready access only to the top of gear reducer  202 . Access panel  215   b  provides principally inspection access to gear reducer shaft  203 , small chain sprocket  206  and chain  207 . For service access to either or both sides of gear reducer  202  usually requires removal of housing  214 , and this can be awkward and time consuming. 
     Rappers are used in various combinations with one another (a large piece of equipment, e.g., a waste-heat boiler supporting a metallurgical furnace, may have more than 100 rappers attached to it), and they are often located (i) at difficult to reach spots on the equipment, e.g., 20 or 30 or more feet above the ground floor, or in a tight corner, or between various components of the equipment, etc., (ii) in close proximity to one another, and/or (iii) at an inconvenient angle (e.g., perpendicular) to the ground floor. As such, the single service access panel (i.e.,  215   a ) to the interior of the assembly may not be available for use or does not provide access to the part or parts that require attention thus necessitating removal of either or both of the gear reducer and hammer assembly housings. 
     With respect to the removal of these housings, the conventional designs do not lend themselves to a facile undertaking of such an endeavor in those instances in which the rappers are located close to one another, or in a tight corner, or Then positioned at an odd angle relative to the floor upon which the equipment rests. For example, gear reducer housing  214  is fastened to hammer assembly housing  211   a  by single, rear bolt  216  and front bolts  217   a  and  217   b  (FIGS. 2,  6  and  8 ). While access to these bolts is almost always available, the removability of the rear bolt is dependent, in part, upon the placement of the rapper relative to the adjacent rapper and/or the equipment to which it is attached. Since the rear bolt is of a length that exceeds the width of hammer assembly housing  211   a , the rapper must be spaced sufficiently apart from at least one of the rappers adjacent to it on either side and from any obstruction on the equipment to allow its withdrawal. Moreover, replacing such a bolt in tight quarters is difficult given the need to align the fastening holes of gear reducer housing  214  with the fastening holes of hammer assembly housing  211   a.    
     In a first embodiment of this invention, access to the rapper components within the gear reducer and hammer assembly housings is improved in two manners. First, better access is provided to the contents within both housings by the addition of access panels  318   a-b  and  319  (FIGS.  3  and  9 ). These housings can contain additional access panels (not shown). Panels  318   a-b  and  319  are of sufficient size and configuration to allow a workman adequate access to the contents of these housings to perform routine inspections and on-site maintenance. The panels can be attached to the housings by any convenient means such as bolts, hinges, tongue and groove fittings, and the like. 
     Second, in those instances in which entry to the interior of the housing through an access panel is inadequate, the housing can be removed with relative ease despite their proximity to other rapper housings or obstructions on the equipment to which the rapper is attached. With respect to the gear reducer housing, the single, long bolt is replaced with short bolts  320   a  and  320   b  (FIGS. 3,  7  and  9 ). Use of the bolts eliminate the difficulty of removing and inserting the single long bolt in tight quarters. 
     With respect to the hammer assembly housing, the fastening arrangement of tabs  221   a-b  on housing  211   b  fitting into slots  222   a-b , respectively, on housing  211   a  (as shown in FIGS.  2  and  6 ), is replaced with the combination of (i) C-slots  325   a  (not shown) and b on housing  211   b  fitting over hanger bolts  327   a-b , respectively, in housing  211   a , and (ii) keepers  323   a-b  fitting into keeper blocks  324   a-b , respectively (as shown in FIG.  3 ). C-slots  226   a  (not shown) and b at the bottom of housing  211   b  engage hanger bolts  228   a-b  at the bottom of housing  211   a , and these remain unchanged from the original design. Removal and replacement of housing  211   b  is thus significantly facilitated in that visual alignment of tab and slot requires neither a top-down perspective nor head or swing space for positioning the tabs into the slots. 
     In another embodiment of this invention, the hammer assembly is improved to allow for more efficient maintenance. As described earlier, the hammer is subject to continuous use and given the nature of its work (i.e., impacting the anvil), its face and the lever and hammer shaft assemblies incur continuous stress and wear. As such, these components require periodic and frequent inspection and attention which occasionally requires removal of either the hammer assembly or at least the hammer. Depending upon such factors as rapper placement on the gas transport or processing equipment and its position relative to other rappers, removal and replacement of the hammer assembly can be difficult at best. The hammer component of the assembly often weighs  100  or more pounds itself and if located high above the floor on which the transport or processing equipment rests, or fitted into a tight position on the equipment, the sheer weight of the assembly makes its disengagement from the other assembly components difficult. 
     According to this embodiment, hammer  105  (FIG. 5) comprises a hammer shell  501  and hammer core  502 . The hammer core is sized to fit snugly within hammer shell  501  such that it essentially fills hammer shell void  503 . When inserted within hammer shell  501 , hammer core  502  is held within it by hammer plate  504  which is fastened to shell  501  by any convenient means, e.g., bolts (not shown). Hammer core  502  is locked in place within void  503  with a bolt and lock nut (neither shown), the bolt threaded through plate  504  such that the end of the bolt engages core face  502   a  such as to secure tightly the core against the end wall (not shown) of void  503 . Preferably, the end wall is about three (3) inches removed from the face of the hammer that strikes the anvil (or in other words, the face of the hammer that strikes the anvil is about 3 inches thick). 
     The hammer core is also sized to constitute a significant, e.g., 50% or more, of the hammer assembly weight. Accordingly, in those instances in which the assembly must be removed for inspection or maintenance, the core can be removed first and this, in turn, reduces the total weight of the remaining assembly for separate removal (and subsequent replacement). Removing and replacing the assembly in this piecemeal fashion greatly assists in the efficiency of the maintenance operation (often allowing one man to do what would otherwise require two or more men). 
     The hammer shell and core can be made in any suitable manner including separate manufacture or creating the core and shell from a single workpiece. As noted above, the core does not extend through the shell such that the core face distal from plate  504  impacts the anvil or in other words, shell void  503  does not extend through hammer shell  501  as a tunnel but rather it extends into it as a cave or recess. The geometry of the core and void can vary to convenience as can their relative position with the shell, e.g., each centered on their respective longitudinal axis, or a variation on this location. 
     In another aspect of this embodiment, the removal and replacement of the hammer assembly from housing  211   a  is further improved by the addition of keeper guide plates  525   a-b  (FIGS. 5,  11  and  3  (shown in phantom-line)) to shaft  512  (one plate on each end of the shaft). The plates are affixed by any conventional means, e.g., threaded bolts through the plate and into an appropriately adapted threaded holes in the end of the shaft, and the plates are sized and configured to fit snuggly into keeper blocks  324   a-b  respectively. The blocks act both as a guide for inserting the hammer assembly into housing  211   a  and when combined with keepers  323   a-b , as a lock for keeping the assembly in place. In a manner similar to the manner in which the plates are affixed to the shaft, the keepers are affixed to the keeper blocks with threaded bolts inserted through keeper faceplates  323   c-b  into threaded holes in the keeper blocks (FIGS.  3  and  11 ). 
     Although better access and ability to inspect and service the rapper is provided by the inventive embodiments described above, from an inspection and service perspective, preferably the rapper is designed to require less of each. Toward this end, another embodiment of the invention is illustrated through a comparison of FIGS. 4 and 5. 
     In FIG. 4, conventional hammer shaft assembly  210  comprises hammer shaft  412  and hammer shaft bushing  418  each with machined grooves  420   a-c  and  421   a-b , respectively. Such grooves require routine maintenance to ensure adequate greasing, and thus periodic disassembly of the hammer shaft assembly. In the improved design of this inventive embodiment (FIG.  5 ), hammer shaft  412  is replaced with hammer shaft  512  and hammer shaft bushing  418  is replaced with hammer shaft bushing  518 , both of which are without grease grooves. Instead, hammer shaft bushings  417   a-b  are replaced with self-lubricating bushings  517   a-b . The maintenance step of greasing the hammer shaft and bushing is thus eliminated (other than replacing a worn bushing the frequency of which is much less than that of manually greasing the shaft and bushing). 
     Another improvement in the hammer shaft assembly design is the manner in which hammer shaft casing  408  engages hammer shaft bushing  418 . In the conventional assembly, casing  408  engages bushing  418  through a compression fit which results from bolting the two casings halves to one another. However, this allows for slippage over time which, in turn, requires maintenance to adjust the casing back to its original fit about the bushing. In contrast, casing half  508   a  carries key  522  on its inside surface which is sized and configured to engage firmly slot  523  on bushing  518 . When this key and slot are joined with one another, the fit between bushing and shaft is much more resistant to slippage than that provided simply through compression alone. 
     Yet another design improvement in the hammer shaft assembly is in the manner in which bushing  418  engages large chain sprocket  208 . In the conventional design as shown in FIG. 4, the bushing is cylindrical and opening  230  is annular and sized to accept bushing neck  418   a  in a snug fit. The bushing is then permanently affixed to the sprocket by any conventional means, e.g., welding one to the other, typically to both faces of the sprocket. However, given the nature of the constant pounding that this equipment not only delivers but also experiences, welds tend to weaken and break over time and this, in turn, results in a temporary decommissioning of the rapper. 
     In this design improvement, the bushing and sprocket opening are keyed to one another by any suitable means, e.g., in FIG. 5 by imparting flat surface  231  to the annulus that defines opening  230  and flat surface  524  to bushing  518 . This key arrangement also eliminates neck  418   a  which, in turn, results in a simpler bushing design. Other key designs are also available, e.g., changing the configuration of opening  230  from circular to elliptical, square, diamond, etc. This key arrangement is best used in combination with the conventional practice of welding and provides a convenient “back-up” system for permanently engaging hammer shaft bushing  518  with large chain sprocket  208 . In other words, if a weld breaks, the rapper can remain operational because the key arrangement prevents slippage between the sprocket and bushing. FIG. 14 provides an end-on-view of bushing  518  engaging sprocket  208  in a keyed arrangement and with welds  1401  and  1402  in place. 
     In yet another design improvement, stop pin  406  on casing arm  409  (FIG. 4) is replaced with stop block  506  (FIG.  5 ). As noted earlier, the function of the stop pin is to engage levers  404   a-b  so that middle bearing  402  will engage in the hammer saddle after the hammer is released. Stop pin  406  is typically made from a soft metal (relative to the metal from which casing arm  409  is made), and it is typically welded to casing arm  409 . However, the constant engagement of the levers has a tendency to weaken and eventually break the pin. Stop block  506  in contrast, offers a larger surface area over which to engage levers  404   a-b , thus enhancing its durability relative to the pin and in a preferred embodiment, it is machined from the same block of metal that forms the casing arm. This further increases the durability of the block as compared to the pin. 
     Although the invention has been described in considerable detail, this detail is primarily for the purpose of illustration. Variations can be made on the invention as described above without departing from the spirit and scope of the invention as described in the appended claims.