Abstract:
Impacting devices are provided to strike the sway frame which supports the filtering bags in a bag house. The impacting devices each include a stationarily-mounted bracket, an externally-threaded sleeve that is adjustably received in the bracket, a bolt-like striker member slidable in the sleeve and a coil spring which biases the striker member to an extended position relative to the sleeve.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to dust collecting devices of the type using bag-like cloth or fabric filtering elements and, more particularly, to a means for cleaning the filtering elements in such devices to discharge accumulated particulates. 
     2. State of the Art 
     It is well-known to accomplish large-scale cleaning of suspended particles from gaseous streams by passing the streams through a device having a housing wherein are suspended a plurality of flexible cloth or fabric filtering elements that are formed as cylindrical bags. Such devices are commonly known as bag houses. After a period of operation, the particles that accumulate on the filtering elements must be removed. That is typically done by shaking or vibrating the elements to dislodge the particles, which then fall into hoppers or other recepticles disposed at the bottom of the housing. 
     A problem with bag-type filters is to effectively clean the elements without undue wear. Typical practice today is to impart a gentle shaking or oscillatory motion to the bag-support structure and, at the same time, to direct a reverse current of air through the elements to loosen the dust accumulations. In applications such as filtering the fumes discharged by cupolas in steel foundries, a gentle shaking action is not sufficient to dislodge the dust that agglomerates on the filtering elements, and more vigorous shaking has been found to be deleterious to the filtering elements, especially those formed of synthetic fabrics such as fiber glass. The vigorous back-and-forth bending eventually snaps the synthetic strands. Workers in the art, however, have found that bags made of synthetic fibers have superior filtering characteristics when used in high-temperature or moist atmospheres or when cleaning certain acidic gases and, accordingly, have sought effective means for cleaning such filtering bags. 
     OBJECTS OF THE INVENTION 
     The primary object of the present invention is to provide improved means for dislodging accumulated particles from the filtering elements in bag-type filtration devices. A more specific object is to provide such means which will clean filtering elements constructed of synthetic fabric without unduly damaging the fabric. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention can be readily understood by referring to the following description and appended drawing, which are offered by way of illustration only and not in limitation of the invention, the scope of which is defined by the appended claims and equivalents to the structure, acts and materials specified hereinafter. In the drawings, 
     FIG. 1 is a pictorial view of the upper section of a bag-type filter device inclusive of a device according to the present invention, and 
     FIG. 2 is an elevational view, enlarged for purposes of clarity, of the device of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The filtering unit shown in FIG. 1 includes a rectangularly-shaped housing having four generally upstanding non-foraminous sidewalls 13-16 that define a cleaning compartment. A movable frame means, generally designated 19, mounted at the top of the compartment supports a plurality of vertically-disposed bag-type filtering elements 23 in spaced-apart relationship. The filtering elements 23 are conventional; they are formed as elongated tubes, have closed tops, are porous and may be made from either cloth or a synthetic fabric. The filtering elements are suspended in tension and their lower ends are stationarily mounted in a manifold plate 24 so that gas to be cleaned is admitted into the interior of the elements. Typically, the gas flow is induced by fans or blowers. With such an arrangement, dust and other particulate matter accumulates on the inside walls of the bags and cleaned gases pass into the space between the bags and thence to discharge upward through the roof of the cleaning compartment. 
     The bag-support frame means 19 is a generally rigid structure. In the illustrated embodiment, the frame includes a plurality of horizonally-disposed beams 25 that extend transversely across the cleaning compartment parallel and in spaced-apart relationship to one another. The filtering bags 23 are individually suspended in tension from the support beams 25, say by conventional hanger members 27. The respective ends of the support beams 25 are pivotally connected to a pair of parallel rigid &#34;driven&#34; beams 29 which, in turn, are supported by depending pivot mechanisms, generally designated 31, connected to the housing&#39;s structural frame to allow the driven beams to move in an oscillatory or swaying manner. 
     Each of the illustrated pivot mechanisms 31 includes an upper support bracket 33 stationarily fixed to the housing&#39;s structural frame and a short link 35 pivotally connecting the bracket to the associated driven beam 29. The pviot mechanisms are located along the sides of the cleaning compartment so as to fully support the driven beams 29 and, hence, the bag-support frame means so that it can sway or oscillate back and forth in a generally horizontal direction. 
     Such oscillatory motion is imparted to the bag-support frame 19 by a drive unit 39 that is connected to at least one of the aforementioned driven beams 29. The particularly illustrated drive unit is a stationarily-mounted rotary motor that is pivotally coupled to one of the driven beams 29 by a working shaft 41 and an eccentric 42 so that rotational motion of the eccentric imparts reciprocative or oscillatory movement to the driven beam and, hence, to the filtering bags 23. It should be understood that other drive arrangements can be utilized to impart a generally positive back-and-forth movement to the filtering bags; for example, a reciprocative piston mechanism could be used. Also, various types of frame-supporting pivot mechanisms can be employed in place of those particularly illustrated. Furthermore, the bags themselves can be supported for oscillatory movement by structures other than the illustrated bag-support frame means. 
     In practice the frequency and amplitude of the oscillations of the bag-support frame are adjustable by means of changing the drive unit speed or adjusting the connecting linkage. Typically, the frequency ranges from 150 to 300 cycles per minute and the amplitude varies from 1/4 to 11/4 inch either side of the center. 
     According to the present invention, impacting mechanisms 45 are provided to cause an impact against the bag-support frame 19 at the extremes of its oscillatory motion; the impacts superimpose shock waves on the gentle swaying motion of the filtering bags and thereby dislodge dust from the walls of the bags. The impacting mechanisms can either be mounted on the housing&#39;s structural frame as shown or can be carried by the bag-support frame means 19; in the former case, the impacting devices will strike the moving frame means and in the latter case would strike the stationary housing frame. Also, the impacting devices can be horizontally disposed as shown or arranged at a slight angle from horizontal. Typically, a single impacting device is located at each end of the travel of the bag-support frame. 
     As shown in FIG. 2, a single one of the impacting mechanisms 45 includes an externally-threaded tubular member or sleeve 47 which is screwed into a receiving bracket 49 that is stationarily fixed on the structural frame of the cleaning compartment. The shank of a bolt-like striker member 53 is slidably disposed within the sleeve 47 and projects substantially from both ends thereof. The striker member 53 is retained in association with the sleeve by its head 55 and by a securing nut 57 threaded onto the end of the shank. A jam nut 59 can be provided to prevent the securing nut 57 from working loose during the operation of the impacting device. A coiled compression spring 61 encircles the shank and, in the illustrated embodiment, is retained between the head 55 and the adjacent end of the sleeve 47 by opposed flat washers 63 and 65. 
     Normally, the impacting mechanism 45 is adjusted so that the spring 61 is placed in compression even when the mechanism is not operating upon the bag-support frame. The amount of precompression on the spring 61 is determined by the distance the nut 57 is drawn onto the shank; the further the nut is taken up, the greater the compressive force on the spring. Typically, the spring compression is about 36 pounds per inches. 
     In operation, the impacting mechanisms are mounted so that the heads 55 strike or butt the bag-support frame just prior to the frame reaching the extremes of its displacement. Normally, the support frame would undergo a gradual de-acceleration at the ends of its travel but, when the impacting devices are utilized, there is a sharp shock or impact felt by the frame at the ends of the stroke. The shock is accentuated because the frame is not perfectly rigid and because there is a certain amount of play in the support mechanisms and in the drive linkage. Vibrations from the shock received by the frame are transmitted to the filtering bags and have been found surprisingly effective in practice to dislodge accumulated particles from the interior walls of the bags 23. The discharged dust falls downwardly for collection in hoppers or the like, not shown, arranged below the manifold plate 24. When the imparting device strikes the frame, the shank 53 is driven to slide back through the sleeve 47 until such a point that the frame reaches the end of its stroke; the reactive force exerted by the impacting device is proportional to the spring displacement and the magnitude of the impact depends in part on the spring stiffness. 
     The impacting mechanism has several adjustments. As already mentioned, the precompression of the spring 61 is adjustable by taking up the nut 57. That adjustment determines the magnitude of the reactive force exerted by the spring against the bag-support frame since spring force is directly or linearly proportional to displacement according to Hooke&#39;s law. Secondly, the stop clearance or shock impact point is selectively determined by screwing the externally-threaded sleeve 47 into or out of the bracket 49. This adjustment also determines the total displacement of the spring 61 during a working cycle. A typical displacement varies from about three-eighths inch to one-half inch. The shock impact point can also be varied by adjusting precompression on the spring, although that is usually preset. These various adjustments of the impacting device allows flexibility in tuning the resultant shock wave for any fabric or dust loading combination, thus making it possible to optimize the cleaning of the filtering elements under differing conditions. 
     As shown both in FIGS. 1 and 2, bumper members or guards 67 can be fixedly carried by the frame means 19 and positioned to hit the striking ends 55 of the impacting devices 45. The bumpers 67 prevent damage to the beams 25.