Abstract:
A duct traversal preparation apparatus that temporarily adheres to a surface to enable hands-free traversal is provided. The apparatus includes scales to accurately locate the positions of traverse holes and a template with a locking device to guide the drilling of the traverse holes. The apparatus also orients a measuring probe to coordinates for accurate and repeatable airflow measurement.

Description:
FIELD 
     Embodiments of the present invention relates to systems and methods for traversing a duct to obtain the volume of air in the duct and the like, and more particularly to systems and methods for reducing the use of reference standards and complex computations associated with the process. 
     BACKGROUND 
     Traversing a duct is the standard method for measuring air velocity in a duct to obtain the volume of air flowing through the duct. Duct traversal is a two step process. First, the duct is prepared to measure the velocity of air at predetermined coordinates within the duct and then the airflow at the predetermined coordinates is measured. To determine air volume, the average velocity is multiplied by the cross sectional area of the duct. 
     To prepare a rectangular duct for traverse, a predetermined number of holes are drilled at predetermined locations across the surface of the duct. To calculate the number and locations of the holes, the width and depth of the cross section of the duct at the point of the traverse is measured using a ruler or tape rule. Once the number and the location of the holes are calculated, the positions of the holes are marked on the duct and thereafter the holes are drilled. 
     To measure the air velocity at the predetermined coordinates, a measuring probe connected to a velocity measuring instrument is inserted into the holes, one hole at a time. More specifically, before measuring the air velocity at the predetermined coordinates, the spacing of the coordinates in the duct is marked on the measuring probe. When the probe is inserted into the duct through a hole, it is oriented to a specific direction within the duct. Then, the air velocity is measured by moving the probe to each predetermined coordinates using the marks on the probe as reference. For accurate measurement, the probe is required to maintain a specific orientation within the duct during each measurement. This process is continued until the airflow has been measured through each hole. 
     Because ducts are generally installed overhead, duct traversal is generally most convenient from the bottom of a duct. But, holding a tape rule to the bottom of a duct to measure and mark the positions of the holes is very challenging. It also is very difficult to drill the holes and prevent the drill bit from walking. These tasks are made even more difficult because they are performed while standing on a ladder and looking upwards. In addition, using duct traverse reference materials and calculating the coordinates could be very tasking in field conditions. 
     While measuring the velocity, a technician is required to orient the probe to predetermined coordinates using the marks on the probe as reference as he pushes the probe Into the duct looking up. This process also takes place while the technician is standing on a ladder with the flow reading instrument dangling from his neck. 
     Although some ducts are installed at an angle, the traversing process is still the same. Developing a practical process or device to accurately determining the air volume in a duct based on the theory of duct traversing has not been achieved due to difficulties associated with duct traversal as discussed above. Consequently, due to the imprecise manner in which duct traversal is performed, the air volume calculated for a particular duct will be different each time air volume is calculated. 
     As discussed above, the process of duct traversal is inefficient and laborious, and multitasking on a ladder makes duct traversal unsafe. Embodiments of the present invention address these problems. 
     SUMMARY 
     Embodiments of the present invention reduce all the engineering formulations involve in duct traversal to a user friendly portable instrument that provides accuracy and repeatability. Embodiments of the present invention adhere and align to the surface of a duct for hands free operation, provides means for measuring the size of the duct, and provides means for determining the locations of the holes for duct traversal. Embodiments of the present invention include means for guiding drill bits to drill perpendicularly and for preventing bits from walking during the drilling. 
     During flow measurement, embodiments of the present invention indicate the locations of the coordinates to measure air velocity and keep the probe oriented appropriately. Embodiments of the present invention allow the probe to be read at eye level and not looking up. Embodiments of the present invention reduce the use of complex calculations and references. 
     Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  illustrates a duct traversal preparation apparatus according to one embodiment of the invention. 
         FIG. 2  illustrates a cross-sectional view of the duct traversal preparation apparatus of  FIG. 1 . 
         FIG. 3A  illustrates a template of the duct traversal preparation apparatus of  FIG. 1 . 
         FIG. 3B  illustrates a cross-sectional view of the template of  FIG. 3A . 
         FIG. 4  illustrates an exemplary cross-sectional side view of the duct traversal preparation apparatus of  FIG. 1  when used in its intended manner with an exemplary duct. 
         FIG. 5A  illustrates an airflow measurement guide of the duct traversal preparation apparatus of  FIG. 1 . 
         FIG. 5B  illustrates an enlarged view of a probe fixture of the airflow measurement guide of  FIG. 5A . 
         FIG. 5C  illustrates a side view of the probe fixture of  FIG. 5B . 
         FIG. 6  illustrates a duct traversal preparation apparatus according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 4  illustrates a duct traversal preparation apparatus  100  according to a preferred embodiment of the present invention. The duct traversal preparation apparatus  100  may include a magnetized plate  10 , a hole preparation guide  12 , and an airflow measurement guide  14 . 
     The magnetized plate  10  provides the primary means for attaching and aligning the duct traversal preparation apparatus  100  to a duct  66 . When the magnetized plate  10  is attached to the duct  66  during use, the magnetized plate  10  is perpendicular to hole preparation guide  12  as shown in  FIG. 4 . 
       FIG. 1  illustrates hole preparation guide  12  and the airflow measurement guide  14  of the duct traversal preparation apparatus  100  in a folded state. As shown in  FIG. 1 , duct traversal preparation apparatus  100  also may include a release pin  18  and carriage  30 . Release pin  18  holds airflow measurement guide  14  to hole preparation guide  12 . Carriage  30  provides a means for moving airflow measurement guide  14  along channel  33  of hole preparation guide  12 . 
     As shown in  FIG. 1 , hole preparation guide  12  may include scales  26 ,  28  and a template  16 . Scale  26  is a scale used for measuring the width of the duct  66 . Scale  28  is a predetermined set of numbers that shows the positions of where the traverse holes should be on the duct based on the duct width read on scale  26 . 
       FIGS. 3A and 3B  illustrates template  16  in greater detail. As shown in  FIG. 3A , template  16  may include a predetermined bore  24 , an arrow  20 , and a locking device  22 . The bore  24  provides a means of guiding drill bit to drilling holes perpendicular to the duct. The arrow  20  is used to line up the bore  24  on the template  16  to the drill position indicators on scale  28 . The locking device  22  keeps the template  16  in a fixed position during the drilling of the hole thereby preventing the drill bit from walking. Hole preparation guide  12  may be strategically magnetized to provide a secondary means of attaching the duct traversal preparation apparatus  100  to the duct  66 . 
       FIGS. 5A-5C  illustrate the airflow measurement guide  14  in greater detail. Airflow measurement guide  14  may provide a means for locating and aligning a measuring probe to predetermined coordinates for accurate airflow measurement. Airflow measurement guide  14  may include scales  34  and  36  and a probe fixture  38 . Scale  34  is a scale used for measuring the depth of the duct  66 . Scale  36  is a predetermined set of numbers that shows the coordinates to measure the airflow that is unique to the depth of the duct read on scale  34 . 
     Probe fixture  38  provides a means for moving the probe in and out of duct  66  and to predetermined coordinates. Probe fixture  38  may include an adjuster  52 , threaded pin with nut  40 , stud  42 , wedge  48 , marker  46 , and handle  50 . The adjuster  52  includes bracket  54  and two slots  44  and provides a means for calibrating the probe fixture  38  with scales  34  and  36 . Bracket  54  holds and maintains the orientation of the probe, while slots  44  provide a means for changing the position of the adjuster  52 . 
     The threaded pin with nut  40  and the stud  42  are attached perpendicularly to the probe fixture  38 . Threaded pin with nut  40  and the stud  42  fit through the slots  44  on the adjuster  52  and provide the means for keeping the adjuster  52  in a predetermined orientation. In addition, the threaded pin with nut  40  provides a means for attaching the adjuster  52  to the probe fixture  38 . The wedge  48  provides a means for holding the probe fixture  38  to a position and the handle  50  is used to hold the probe fixture  38 . The marker  46  provides a means of lining up the probe to its coordinates on scale  36 . 
     As discussed above, there are two distinct activities in duct traversing—duct prep and airflow measurement. The two activities may not necessarily be performed at the same time. The duct prep is done first and only once, while the flow measurement could be on-going and as such each of the activities can have separate instrument configured in a variety of ways.  FIG. 6  illustrates a duct traversal preparation apparatus  200  according to an alternate embodiment of the present invention. 
     Duct traversal preparation apparatus  200  attaches to duct  66  just like duct traversal preparation apparatus  100 . Duct traversal preparation apparatus  200  can be used to read duct width, locate positions of traverse holes, and guide the drill bit to bore perpendicular holes. Duct traversal preparation apparatus  200  comprises a template  56  with a plurality of rows  58  of bores  60 , whereby each row  58  represents a duct width and the bores  60  are the locations of the traverse holes. The centerline  62  connects the bores  60  on the same row for clarity and ease of use in field condition. Scale  64  provides the means of reading the duct width. 
     A method of operating the duct traversal preparation apparatus will now be described. With duct traversal preparation apparatus  100  facing down, unfold magnetized plate  10  to an upright position. Then, attach duct traversal preparation apparatus  100  to duct  66  by holding the bottom of the duct traversal preparation apparatus  100  to the bottom of duct  66 , with magnetized plate  10  on the side of duct  66 . The duct traversal preparation apparatus  100  will align itself to duct  66 , by design. 
     To locate and drill traverse holes, read the width of the duct  66  on scale  26 . Then, slide the template  16  along the channel  32  stopping at each location on scale  28  at which the arrow  20  on the template  16  points to the number corresponding to the width of the duct obtained in scale  26 . At each of the locations, drill a hole on the duct  66  through the bore  24 , locking down the template  16  as necessary to prevent it from moving. For example, if the width of the duct  66  was determined to be 18″, then drill a hole at every location that the arrow  20  on the template  16  points at the number  18  on scale  28 . After drilling, the holes are plugged with caps to prevent air leakage. The channel  32  is sized to stride the caps such that the accuracy of the hole can be collaborated with the caps on. 
     To perform air velocity measurement, release airflow measurement guide  14  by pulling the release pin  18 . insert the nozzle of the probe into a hole in the duct  66  and with the nozzle resting on the floor of the duct  66 , push the leg of the probe into the bracket  54 . If the probe fixture  38  is not lined with scales  34  and  36 , calibrate the probe fixture  38  by loosening the nut  40  to adjust bracket  54 . Once calibrated, move the probe fixture  38  until the probe reaches the ceiling of the duct  66  and read the depth of the duct  66  on scale  34 . Slide the probe fixture  38  along channel  68  to each location on scale  36  with the same number as the depth of the duct  66 . These are the coordinates where the airflow would be read. Repeat the procedure at each hole. For example, if it was determined that the depth of the duct was 12″ on scale  34 , then the coordinates would be at every point on scale  36  where the arrow on the probe fixture lines up with the number. 
     Many modifications and other embodiments of the invention will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the forgoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.