Abstract:
An articulating water monitor-cleaning device for cleaning internal surfaces of large-scale combustion devices. The device is mounted to the exterior of a wall of a combustion device and positions a water spray lance to direct a stream of water against internal surfaces over a range of position. Pairs of orthogonally oriented four-bar linkage assemblies are provided, each having rotary actuators. The relative position between a pair of joints affixed to the lance tube allows the position of the lance to be set over a range of positions.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This specification claims priority to U.S. Provisional Patent Application No. 60/279,066, filed on Mar. 27, 2001, entitled “Articulating Water Monitor Cleaning Device”. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a fluid spraying monitor and, in particular, to one adapted for use in cleaning internal surfaces of large-scale combustion devices. 
     During the operation of large-scale combustion devices, such as boilers burning fossil fuels, slag and ash encrustations develop on internal surfaces of the device. The presence of these deposits degrades the thermal efficiency of the combustion device. Therefore, it is periodically necessary to remove such encrustations. Various techniques are presently used. In some cases, vibration is used to mechanically remove such deposits. Devices referred to as “sootblowers” are used to project a stream of a fluid cleaning medium, such as air, steam or water, against the internal surfaces. In the case of long retracting type sootblowers, a lance tube is periodically advanced into and withdrawn from the boiler and articulated to rotate or oscillate to direct one or more jets of cleaning medium at desired surfaces within the boiler. Sootblower devices are also used which are stationary and maintained in a position within the boiler. Sootblower lance tubes project through openings in the boiler wall, referred to as wall boxes. In cases where it is desired to clean the interior wall area surrounding the wall box, so called wall blowers are used. These devices incorporate a lance tube with nozzles directed back at the wall through which the lance tube is projected. 
     Another class of boiler cleaning devices is used which are designed to clean a wall surface other than the one in which the wall box is installed using water as the cleaning fluid. These devices are sometimes referred to as “water cannons”. They involve the use of a monitor or nozzle positioned within a wall box that creates a jet of water or another fluid which passes through a portion of the interior of the boiler and strikes an opposing wall or other surface to be cleaned. Early versions of these devices were manually articulated to allow the stream to be aimed at particular areas to be cleaned. More recently, however, articulating devices operated under programmed numerical control periodically cause the water cannon lance to trace a prescribed spray pattern on the opposing wall or other surface to be cleaned. This invention is related to such a water cannon device which will also be referred to in this description as an articulating water monitor cleaning device. 
     In accordance with this invention, an articulating monitor-cleaning device is designed principally for ejecting water which incorporates a pair of orthogonally oriented articulating four-bar linkages which are mechanically actuated. One of the linkage arms or links is coupled to the lance tube near its inlet end. The other discharge end of the lance tube where a nozzle is present is mounted to the wall box and is allowed to freely pivot at the wall box. Using a pair of rotary actuators, each of the pairs of four-bar linkages can be actuated to a prescribed angle. By adjusting the angles of the four-bar linkages, a prescribed aiming position on the lance tube can be achieved. Under programmed control, a desired motion sequence can be executed to trace a desired pattern for the jet ejected from the water lance. 
     The device according to this invention further includes mechanisms to improve the mechanical stability of the drive. This is principally achieved by providing redundant four-bar linkages which are not driven but follow the motion of the actuated or driving four-bar linkage. The geometric relationship of the elements comprising the four-bar linkage are selected such that movement of an actuating axle translates directly to an equivalent motion of the lance tube over a range of motion. This is achieved by four-bar linkages which are based on links defining a parallelogram, that is, opposing links have equal lengths. Another feature of this invention provides a system including a subassembly which can be conventionally mounted to the associated boiler. 
     Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial view showing the fully assembled articulating water monitor cleaning device in accordance with this invention. 
     FIG. 2 is a side elevational view of the articulating water monitor cleaning device shown in FIG.  1  and further including a cross-sectional view through an associated boiler wall; 
     FIG. 3 is a side elevational view similar to FIG. 2 but showing the device articulated in the horizontal direction to change the aiming direction of the water lance; 
     FIG. 4 is another side elevational view similar to FIG. 3 but with certain components removed to more clearly reveal the elements associated with the water lance component; 
     FIG. 5 is a top elevational view of the articulating water monitor cleaning device shown in FIG. 1 further illustrating a portion of the boiler wall in section; 
     FIG. 6 is a top elevation similar to FIG. 5 but showing the device in an articulated position in the vertical direction to change the aiming direction of the water lance; 
     FIG. 7 is a side sectional view taken through the boiler wall showing the seal box assembly mounted to the boiler wall; 
     FIG. 8 is a top sectional view through the boiler wall also showing the seal box assembly mounted to the boiler wall; 
     FIG. 9 is a front view of the seal box assembly mounted to the associated boiler wall; 
     FIG. 10 is a frontal view of the Cardon joint element described in connection with this invention; and 
     FIG. 11 is a pictorial view of the Cardon joint shown in FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The cleaning device in accordance with this invention is generally designated by reference number  10  and is shown mounted to a boiler wall  12  in the figures. The details of boiler wall  12  are best described in connection with FIGS. 2 through 6. Boiler wall  12  includes an outer protective metal sheeting layer  14  and a plurality of steam pipes  16  exposed to the interior of the associated boiler. Insulation layer  18  separates sheeting layer  14  from steam pipes  16 . Steam pipes  16  are provided for transferring heat from the internal combustion process as part of the thermal conversion process of the overall system. A portion of the boiler wall  12  includes a through port allowing installation of cleaning device  10  and is generally referred to as a wall port  20 . Additional details regarding wall port  20  are provided later in this description. 
     Cleaning device  10  principally includes stabilizing ring assembly  22 , horizontal motion actuator assembly  26 , vertical motion actuator assembly  24 , and water lance  28 . These elements and their associated components will be described in greater detail as follows. 
     The basis of operation of cleaning device  10  is through controlling the directional orientation of water lance  28  through vertical and horizontal displacement of stabilizing ring assembly  22 . Water lance  28  is mounted at its water discharge end where a nozzle is present in wall box assembly via Cardon joint  30 . Another Cardon joint  32  is in turn supported by stabilizing ring assembly  22  and supports water lance  28  at near its water inlet end. Cardon joints  30  and  32  are hinge devices which allow the freedom of rotation about two non-parallel axes such as vertical and horizontal axes. Thus, these devices operate much like convention universal or “U-joints”. As the position of Cardon joint  32  is moved to various positions, water lance  28  is caused to undergo a change in direction. Cardon joint  30  is illustrated in more detail in FIGS. 10 and 11. Cardon joint  30  includes mounting plate  34  and a pair of concentric rings, including inner ring  36  and outer ring  38 . Inner ring  36  is mounted to water lance  28  about an associated mounting flange. Inner ring  36  is able to rotate with respect to outer ring  38  about a vertical axis defined by pins  40 . Outer ring  38  is able to rotate relative to mounting plate  34  about a horizontal axis defined by pins  42 . This configuration permits the angular motion described previously. Cardon joint  32  is assembled in a manner substantially identical with that of Cardon joint  30  but is configured for mounting to stabilizing ring assembly  22 . As explained in more detail in the following description, water lance  28  is rigidly mounted to the inner ring of Cardon joint  32 , and mounted for sliding engagement with the inner ring  36  of Cardon joint  30 . 
     Movement of stabilizing ring assembly  22  in the horizontal direction is caused by horizontal motion actuator assembly  26  which includes a motion actuator in the form of gear reducer motor unit  44  which causes controlled angular rotation of axle  46 . As axle  46  undergoes angular rotation, swing arm assembly  48  also is caused to rotate about a vertical axis. Swing arm assembly  48  is, however, freely permitted to rotate relative to axle  46  about a horizontal axis vertically when stabilizing ring assembly  22  undergoes vertical motion. Swing arm assembly  48  includes bearing  50 . Swing arm assembly  48  is in turn coupled with stabilizing ring assembly  22  via flexible or universal joint  52 . 
     Since there is some change in the distance between Cardon joints  30  and  32  during position changes of water lance  28 , Cardon joint  32  supports thrust loads acting on lance  28 , whereas the lance  28  is permitted to slip axially with respect to Cardon joint  30 . 
     The cleaning medium leaving water lance  28  imparts a thrust force on the lance. In accordance with this invention, lance tube  28  is restrained at the outboard Cardon joint  32 , and is allowed to slip axially with respect to the inboard Cardon joint  30 . Accommodating the thrust load by the outboard Cardon joint  32  means that the potential for friction wear and galling is born by the Cardon joint  32 , removed from the heat of the associated boiler. Wear characteristics of the materials and components making up Cardon joints  30  and  32  are strongly dependent on temperature. Considering the great difference in temperature between the inboard and outboard Cardon joints  30  and  32 , respectively (i.e., approximately 1,000° F. versus approximately 300° F.), the wear and service characteristics of this system are enhanced. 
     At a position on stabilizing ring assembly  22  diametrically opposite the point of connection of universal joint  52 , another flexible or universal joint  56  is provided. This universal joint  56  is mounted at one end of linkage arm  58 , which is mounted on its opposite end via U-joint  60  to mounting plate assembly  100 . 
     Vertical motion actuator assembly  24  is comprised of components substantially identical with that of horizontal motion actuator assembly  26  and consequently includes a motion actuator in the form of gear reducer motor unit  64 . Motor unit  64  drives axle  66  for controlled rotation movement, which carries swing arm assembly  68 . Bearing  70  mounts the swing arm assembly  68  to axle  66 , but allows free movement of stabilizing ring assembly  22  in the horizontal direction. Thus, the swing arm assembly  68  is permitted to rotate relative to axle  66  about an axis normal to axle  66 . The lowermost portion of stabilizing ring assembly  22  is the connection point for swing arm assembly via universal joint  72 . At the uppermost segment of stabilizing ring assembly  22 , linkage arm  76  is connected at its opposite ends with the stabilizing ring assembly  22  and mounting plate assembly  100  via U-joints  74  and  78 , respectively. 
     With specific reference to FIG. 1, stabilizing ring assembly  22  includes outer ring  82 , inner ring  84 , and four spokes  86  connecting the two rings. Inner ring  84  is located on a plane displaced from that formed by outer ring  82  toward wall port  20 , for reasons which will be described in more detail later in this description. Although outer ring  82  is shown having a circular shape, other shapes could be provided. For example, outer ring  82  could be square in shape formed by straight sides connecting between spokes  86 . 
     Since the angular position of axles  46  and  66  is important in establishing the direction of water lance  28 , shaft encoders or resolvers  88  and  90  are provided. Resolvers  88  and  90  provide electrical output establishing the rotated position of the associated axles  46  and  66 . These outputs are used with a controller system for cleaning device  10 . Motor units  44  and  64  cause rotation of the associated axles  46  and  66  based on control inputs. Due to a high reduction gearing, motor units  44  and  64  inherently resist changes in position of axles  46  and  66  in response to external forces. Thus, axles  46  and  66  will remain in a set angular position without energizing motor units  44  and  64 . 
     Cleaning device  10  is supported against boiler wall  12  through seal box assembly  23 . Seal box assembly  23  includes base plate  94 , best shown with reference to FIGS. 7,  8 , and  9 . Base plate  94  is fastened to boiler wall sheeting layer  14  and includes an inward deflected port  96 . A plurality of studs  98  protrude from base plate  94 . During installation of cleaning device  10  onto boiler wall  12 , base plate  94  is first mounted to the boiler wall by welding or mechanical fasteners (not shown). 
     Mounting plate assembly  100  has the various components described previously, including gear reducer motor units  44  and  64  mounted thereto. Mounting plate assembly  100  includes bores  102  which correspond in position to protruding studs  98  of seal box assembly  23 . Thus, after base plate  94  is fastened to boiler wall  12 , mounting plate assembly  100  can be readily placed in position and nuts or other fasteners are used to secure the device against seal box assembly  23 . Mounting plate assembly  100  provides a stable platform for mounting of components of the system, and maintaining their alignment. Mounting plate assembly  100  can be fabricated and assembled to boiler wall  12  as a subassembly in a convenient manner. 
     Since it is desired to isolate the interior of the boiler from the exterior, bellows seal  104  is used and connects between mounting plate assembly  100  and water lance  28 . Bellows seal  104  allows for a range of angular motion of water lance  28  yet seals the wall port  10  from gases escaping from the boiler. 
     Operation of cleaning device  10  will now be described with reference to the figures. When it is desired to cause the spray of water emitted from water lance  28  to move horizontally, gear reducer motor unit  44  is actuated to cause angular displacement of axle  46 . This motion in turn rotates swing arm assembly  48 , which causes stabilizing ring assembly  22  to be displaced in the horizontal direction. This movement is depicted in FIGS. 5 and 6. The plane of stabilizing ring assembly  22 , outer ring  82  (and inner ring  84 ) remains parallel with that defined by base plate  94  through the articulation of linkage arm  58 . During the horizontal displacement of stabilizing ring assembly  22 , swing arm  68  freely rotates about its bearing  70 . 
     In a manner similar to articulation in the horizontal direction, vertical displacement is driven by motor unit  64 , which controllably rotates axle  66 . When this occurs, swing arm assembly  68  is actuated such that U-joint  72  is moved in the vertical direction. As previously described, the plane of stabilizing ring assembly  22  remains parallel to base plate  94  through the articulation of linkage arm  48 . FIGS. 3 and 4 illustrate stabilizing ring assembly  22  shifted upwardly. 
     In order to simplify the control approach for the motion of the water monitor cleaning device  10 , it is desirable that a constant relationship exists between the angular motion of axles  46  and  66  and the angular position change for water lance  28 . The articulation of water lance  28  in both the vertical and horizontal directions can be thought of as being generated by a pair of parallelogram four-bar linkages. Vertical motion is actuated by a four-bar linkage, which is shown in simplified terms by the links drawn in phantom lines in FIG.  2 . Swing arm  68  and the lance tube  28  constitute parallel and opposite links  106  and  108 , whereas the associated stabilizing ring assembly spoke  86  and the structure of mounting plate assembly  100  comprise the opposing parallel links  110  and  112 . Links  106  and  108  are equal in length to one another, as are links  110  and  112 . FIG. 2 illustrates the position of the links in a normal non-articulated position of the unit in which case water lance  28  is oriented in a direction normal to that of boiler wall  12 . In order to reduce, to the practical extent, the size of wall port  20 , it is necessary to mount Cardon joint  30  at the position illustrated in FIG. 2, which is immediately adjacent steam pipe  16 . Due to packaging limitations, it is not practical to mount axle  66  in that same plane. In order that links  110  and  112  remain parallel throughout the range of motion of the device, it is necessary for stabilizing ring assembly  22  to have the configuration illustrated in which inner ring  84  is displaced from outer ring  82 . With this configuration, the angular positions of links  106  and  108  always remain equal to one another throughout the range of motion, as do links  110  and  112 . The horizontal motion actuators and associated linkages have the identical parallelogram four-bar linkage described in FIG.  2 . 
     Due to positive actuation of motor unit  64  which causes swing arm assembly  68  to be rotated to a desired angular position, the cooperation among links  106  and  112  establishes the angular position of water lance  28 . Accordingly, the parallelogram four-bar linkage provided by links  106 ,  108 ,  110 , and  112  can be thought of as constituting a driven or actuated four-bar linkage. Although these elements above are sufficient to establish the position of water lance  28 , it is desirable to provide enhanced stability of cleaning device  10 . Due to the inherent backlash and clearances provided by each of the connected articulating joints, the use of actuated four-bar link  114  is augmented through the use of a parallel, non-actuated four-bar linkage  116 . Non-actuated four-bar linkage  116  is defined by link  108 , which is shared with actuated four-bar linkage  114  and opposing link  118  provided by arm  68 . An opposed pair of links  120  and  122  formed by a spoke  86  and mounting plate assembly  100  complete the linkage assembly. As in the case of actuated four-bar linkage  114 , non-actuated four-bar linkage  116  is also a four-bar parallelogram linkage assembly. Throughout the range of motion, links  106 ,  108 , and  118  always move in unison and undergo an equivalent angular change of direction during actuation. Similarly, links  108  and  118  remain mutually parallel, as do links  120  and  122 . Non-actuated four-bar linkage  116  merely follows the motion driven by actuated four-bar linkage  114  since the interconnection between each of the links of non-actuated four-bar linkage  116  is through low friction bearings and none are positively actuated. Since the four-bar linkages  114  and  116  share a common element, namely link  108 , they are said to be parallel and coupled four-bar linkages. 
     This concept of coupling between actuated and non-actuated four-bar linkages and their interrelationship to enhance stability is true in precisely the manner described above in connection with the horizontal motion actuator assembly  26 . This symmetry is evident, particularly with reference to FIG.  1 . In that case, the actuated four-bar linkage is comprised of links defined by swing arm assembly  48  and water lance  28  and additionally by a spoke  86  and the structure of mounting plate assembly  100 . The non-actuated four-bar linkage is in turn also comprised of links defined by linkage arm  58  acting with water lance  28 , as well as the associated stabilizing ring assembly spoke  86  and mounting plate assembly  100 . 
     Through coordinated actuation of the vertical and horizontal motor units  64  and  44 , a range of angular positions for water lance  28  can be provided. FIGS. 3 and 4 illustrate stabilizing ring assembly  22  displaced to a vertical upper position and FIG. 6 shows displacement in the left hand position. In a similar manner, this displacement can occur to the right and lower positions. Thus the range of motion of stabilizing ring assembly  22  can be defined as a square or rectangle when viewing the unit in a frontal elevational view. It may be also be located at any position within the area prescribed by such a square or rectangle and thus a range of positions can be achieved for water lance  28 . 
     The cleaning device  10  in accordance with this invention enables the vertical and horizontal motion of water lance  28  to be accomplished purely through the use of rotary motion actuators  44  and  64 . The four-bar linkages described previously convert the rotational motion of actuators  44  and  64 , which are fixed in their position into the controlled motion of the outboard Cardon joint  32  through a set of spherical coordinates having a fixed radial dimension. This radial coordinate is the length of the linkage system between the inboard and outboard Cardon joints  30  and  32 . The use of rotary motion actuators provides a number of significant benefits over prior art systems, which typically rely on linear actuators. Linear actuator systems, or systems utilizing an X-Y coordinate actuator system, are more subject to contamination, jamming, and wear. 
     While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.