Patent Publication Number: US-2022228823-A1

Title: Direct Drive for HVAC Air Duct Cleaning System

Description:
FIELD OF THE INVENTION 
     The present invention is directed, in general, to an air duct cleaning system and, more specifically, to an improved drive mechanism for an air duct cleaning system for removing dust and debris from air conditioning and heating ducts, dryer vent ducts, etc., of residential and commercial buildings. 
     BACKGROUND OF INVENTION 
     So called “house dust” is widely considered by experts to pose health hazards to persons with allergies, asthma, or respiratory disorders and diseases. House dust may contain dirt, textile fibers, pollen, hair, skin flakes, residue of chemical and household products, cat and dog dander, decaying organic matter, dust mites, bacteria, fungi, viruses, and a variety of other contaminants. Literally, pounds of house dust accumulate on vents and in ducts that comprise the ventilating systems of both residential and commercial buildings. This house dust is becoming increasingly more harmful as Americans spend a larger percentage of their waking hours indoors, often aggravating allergies of the inhabitants. Modern heating/ventilating/air conditioning (HVAC) systems typically incorporate air filters either just prior to the circulation fan of the systems or in the return ductwork. However, most often these filters comprise fiberglass or similar media that are reasonably effective against large debris, but are often inadequate in removing fine particulate matter, such as dust, dander, etc., from the circulated air. Such filters may trap as little as twenty percent of the particulate matter circulating in a ventilation system, allowing the remaining dust and debris to circulate in the household or work place. Additionally, it is not uncommon to encounter ductwork that has been improperly installed or maintained. These ducts frequently leak, allowing dust and debris from the duct surroundings to enter the ducts. Often this is a major contributor to duct contamination. 
     One known approach to remove accumulated debris in ventilation ducts has been to use a rotating brush at the end of a flexible vacuum hose that is fed into each duct from each register location. The hose is fed into an the ductwork of the HVAC system from one or more access points, and as the rotating brush agitates and knocks loose the accumulated debris, and very strong vacuum pulls the loose debris into the hose, through which it travels to the main unit where it is collected. 
     SUMMARY OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION 
     Certain improvements are disclosed for a drive mechanism for coupling a rotatable drive cable to a remote tool, especially for a heating/ventilating/air conditioning (HVAC) air duct cleaning system, having an angled inlet for connecting a remote tool via a rotatable cable, a cable connector guide aligned with the angled inlet for receiving a connection end of the rotatable cable, and a motor such as a brushless direct current (DC) motor with a direct-drive coupling to the connection end of the rotatable connector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee. The figures presented herein, when considered in light of this description, form a complete disclosure of one or more embodiments of the invention, wherein like reference numbers in the figures represent similar or same elements or steps. 
         FIG. 1  provides a side cut-away view of an example embodiment of an improved drive mechanism according to the present invention. 
         FIG. 2  provides a generalized functional block diagram of a conventional HVAC air duct cleaning system improved to include at least one example embodiment of the present invention. 
         FIG. 3  depicts an angled view rendered in color-coded three-dimensions of a portion of an HVAC air duct cleaning system main unit improved to include at least one example embodiment of the present invention. 
         FIG. 4  illustrates a side cut-away view, similar to that of  FIG. 1 , except rendered in color-coded three-dimensions of a portion of an HVAC air duct cleaning system main unit improved to include at least one example embodiment of the present invention. 
         FIG. 5  illustrates a side solid view, similar to that of  FIG. 1 , except rendered in color-coded three-dimensions of a portion of an HVAC air duct cleaning system main unit improved to include at least one example embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF ONE OR MORE EXEMPLARY EMBODIMENT(S) OF THE INVENTION 
     The present inventor has recognized that existing drive mechanisms for providing rotational energy to the brush head of an HVAC air duct cleaning system fail to meet all needs in the present market place. In general, HVAC air duct cleaning systems known to be currently available provide a man-portable main unit which often is mounted on a wheeled cart due to their size and weight. Developing enough negative air pressure (vacuum) to forcefully draw in air from a 3″ or 4″ diameter hose of 35 feet or more in length requires considerable electric motor power. Those motors are heavy. Further, the main unit must provide some sort of rotational drive mechanism to a rotating cable which extends from the main unit, down the length of the hose section(s), and to the power brush head, where it is converted to rotating energy at the brush. In some known systems, the same electric motors which are used to develop the strong vacuum are also used to generate the rotational energy for driving the cable to the power brush head. This is known in at least one system to be accomplished by coupling one of several alternating current (NC) electric motors through a pulley-on-pulley arrangement to the main unit&#39;s hose cable connection. 
     However, the present inventor has realized that there are a number of performance short comings in such an A/C belt-driven system. For example, if the power brush head becomes jammed or in a bind to a degree greater than the force exerted on the rotating cable, the binding force can be transmitted back to the pulley-on-pulley coupling, and to the NC vacuum motor itself. This means that the NC vacuum motor will be slowed or even stalled, which generates a power consumption surge by the NC motor and a drop in vacuum pressure. The pulley-on-pulley coupling can be configured such that it slips at this level of binding and thereby allows the A/C motor to resume turning, albeit perhaps still at a reduced speed and a reduced vacuum generation. 
     Further, in at least one configuration, the pulley-on-pulley coupling can be provided with a clutch device which disengages the pulley from the armature of the NC motor when the binding or resisting force hits a particular threshold. While this is an effect design technique to release the motor from mechanical coupling to the jammed power brush head, it does nothing to help un-bind the power brush head. 
     As such, it requires considerable skill by the operator when pushing a power brush head through ductwork without visual observation of the brush&#39;s condition to listen to the A/C motor&#39;s operation, detect when a brush may be entering a bind, withdraw the hose slightly and reposition or rotate it, and then reattempt advancing the hose into the ductwork. 
     The present inventor has realized that there are a number of disadvantages to this approach, and have set about improving the overall usability of such HVAC air duct cleaning systems to allow them to be used effectively by both experienced and novice operators, to maintain a constant vacuum pressure regardless of the brush head&#39;s condition, to allow for greater control of the brush head&#39;s rotational speed independent of the vacuum pressure generated, and to allow for automation of many of the anti-stall, anti-bind functions traditionally implemented by experienced system operators. 
     Referring now to  FIG. 2 , a generalized functional block diagram is shown of an HVAC air duct cleaning system  200  incorporating the improvements according to the present invention. The present improvements will be readily employed in other systems of other configurations, so this generalized block diagram is provided as an example embodiment according to the invention, which is non-exhaustive of all other embodiments of the present invention to improve other HVAC air duct cleaning systems. 
     A main unit includes, generally, one or more impeller drive motors  215  which rotate one or more impellers  214  to generate a strong negative air pressure in a vacuum chamber  213  which air and debris are collected. The debris may be separated from the air in which it is suspended by a number of conventional means, such as but not limited to air filtration, cyclonic action, settling, etc., into a debris collector  219 . The air, with most of the debris removed, is exhausted from the main unit via one or more vents or exhaust hoses  218 . 
     The air and air-suspended debris are received from the dirty building ducts  210  through the external hose with the power brush head  211  via one or more internal air and debris conduit(s)  212 . According to at least one embodiment of the present invention, the system is improved by providing a new brush head cable drive mechanism  202  including a direct current (DC) brushless motor which is separate and apart from the impeller drive motor(s), thereby achieving a first improvement by separating the vacuum power performance from the power brush head performance. If the power brush head gets slowed or bound to a stop, it will couple back to the new DC brushless motor, but will not interfere with the continued vacuum generation of the impeller drive motors, thereby maintaining full vacuum suction and keeping the collected debris aloft. 
     Still further, according to this particular example embodiment of the invention, the hose fitting, which is the interconnect between the external hose  211  and the main unit, is improved to receive the rotational energy developed by the new DC cable drive motor  202 , with certain additional improvements in preferred embodiments which will be discussed in greater detail in the following paragraphs. The various available embodiment functions can therefore provide certain signals to a system controller  216 , such as a microprocessor-based controller unit, and accompanied by certain control panel  217  improvements, which can, for example but not limited to, display the status of the power brush head, and the vacuum suction level of the system during operation. Further, while the system controller may be enabled to be dynamically capable of adjusting the control of the DC cable drive motor, it is also enabled, in some embodiments, to perform certain anti-stall and anti-bind functions automatically according to shaft movement feedback received from the cable drive motor  202 . In some other embodiments, some or all of the additional control features may be omitted and still fall within the spirit and scope of the present invention of an improved direct drive mechanism for an HVAC air duct cleaning system. 
     Referring now to  FIG. 1  which illustrates a cut-away side view of a portion  102  of a main unit for an improved HVAC air duct cleaning system according to at least one embodiment of the present invention. An external hose fitting  105  is provided on an external panel of the main unit, into which air and suspended debris  103  are pulled using the negative air pressure generated by the main unit. This air and suspended debris is received into at least a first portion of conduit  104  which provides a mechanical angle that generally points the connected hose in a 45 degree angle from horizontal (or from vertical), more or less, which facilitates directing of the hose into ducts which are often above waist or shoulder level of the operator. 
     The air flow, with suspended debris, is then transitioned in direction through an elbow portion  104 ′ of the internal conduit to a generally horizontal direction of flow  103 ′ through a generally horizontal portion  104 ″ of the conduit towards  103 ″ the air/debris separator and collector in the main unit. In at least this example embodiment, the cross-sectional area of the conduit remains fairly constant through the portions  104 ,  104 ′ and  104 ″, thereby inducing no considerable change in the velocity of the flow  103  of the air and suspended debris at the coupler  105  to the flow  103 ′ following the elbow to the flow  103 ″ into the air/debris separator and collector (not shown in this view). 
     In this improved cable drive sub-system  100 , a DC brushless motor  101  is directly coupled  108  to the drive cable  107  for providing rotational energy  107 ′ to the power brush head at the end of the attached external hose (not shown in this view). This drive cable is positioned within the hollow interior of the external hose, and a portion of the drive cable  107  extends from the end of the external hose far enough to be received into the coupling  108 . Typically, the end of the cable is provided with a “stab-in” connector, such as a D-shaped rod which is received into a corresponding D-shaped reception cavity. In this particular example embodiment, the connection end of the drive cable is received into the drive mechanism  100  at an angle approximately perpendicular to the main unit&#39;s panel on which the hose connector  105  is mounted. 
     Still further in  FIG. 1 , it is shown that this example embodiment includes two structural reinforcement panels  112  and  115  which provide support between the two generally cylindrical portions of the unit  100 , of which one of the cylindrical portions  104 ′,  104 ″ serves as an air and suspended debris conduit and the other cylindrical portion serves as a guide to receive the connection end of the drive cable  107  into the coupler  108 . In this example configuration, the DC brushless motor  101  is mounted with its output armature or shaft in direct alignment with the coupled  108  connection end of the drive cable  107 . This co-axial alignment of the motor output shaft to the drive cable minimizes energy lost which otherwise would occur in coupling arrangements that include pulleys, differentials or angle gear boxes. Electrical signal and power cables  110  receive power from the system controller  216 , if present, and provide shaft rotation sensor information to the system controller  216 , if present, where certain improved control methods may be performed as previously mentioned. 
     As illustrated in this particular example embodiment, several improvements are achieved and enabled by this direct-drive arrangement. First, as it is more compact with fewer components than prior designs using pulleys and belts, it enables the external connection to the cleaning hose to project from the main unit at an angle, rather than horizontally or vertically, which is better for most cleaning situations where the entry ducts are in a ceiling or along a top of a wall. Second, the conduit section which allows for insertion of the cable drive rotational energy into the plenum connected to the external hose has just one elbow or bend in it, thereby reducing cavitation and air flow velocity changes and keeping debris suspended in the moving air better. Third, the new drive mechanism is provided in such a manner that it can be connected to existing vacuum generation chambers of existing HVAC air duct cleaning systems, and requires no changes or upgrades to those other subsystems of legacy main units. 
     Fourth, by employing a brushless DC motor, more torque at lower speeds is provided to the power brush head at speeds which are independent of the vacuum-generating induction motor, thereby allowing for greater degrees of control and new automatic features not previously possible with the existing HVAC air duct cleaning systems. 
     Fifth, by employing a sensor to detect the status of the drive cable, and thereby the status of the DC motor and the power brush, such as a hall effect sensor or shaft encoder, a new system controller can be provided (or improved) to include new constant-power, anti-stall, auto-reverse, and auto-unjam features not possible with legacy systems. 
     Finally, existing 3″ twist-lock external hoses with drive cables contained in their hollow interiors and existing air/debris separation subsystems such as a HEPA air filter can be used with the exemplary embodiment set forth in the foregoing paragraphs. 
       FIGS. 3, 4 and 5  provide various views of the foregoing exemplary embodiment rendered in color and provided with shading to represent three-dimensional shapes of certain components and portions. In  FIG. 3 , a semi-transparent main unit portion  102  is shown at a slight angle such that a control panel  109  is visible. The improved drive unit  100  is rendered in solid representation (brown), including the support panels  112  and  115 , the conduit portions  104 ,  104 ′, and  104 ″, and the cable coupling guide  114 . The brushless DC motor  101  is painted in blue, which is mounted and coupled  108  (components within the red dashed oval) in a co-axial alignment between the motor output shaft and the drive cable  107  connection end (yellow). Other elements of the legacy system are shown in various shades of gray. 
       FIG. 4  shows the same side-cutaway view as  FIG. 1 , except in color according to  FIG. 3 , with a view into the interior (green) of the conduit portions  104 ,  104 ′, and  104 ″ of the improved example embodiment  100  of a direct-drive subsystem.  FIG. 5  is the same view as  FIG. 4 , except the conduit portions  104 ,  104 ′, and  104 ″ are rendered in solid representation (brown). 
     The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof, unless specifically stated otherwise. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. 
     Certain embodiments utilizing a microprocessor executing a logical process may also be realized through customized electronic circuitry performing the same logical process(es). The foregoing example embodiments do not define the extent or scope of the present invention, but instead are provided as illustrations of how to make and use at least one embodiment of the invention.