Abstract:
A duct stretcher that is used to conveniently bring the joining ends of a sheet metal air carrying duct system together so that the two ends can be joined and essentially sealed.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a duct stretcher that is used to bring the joining ends of an air carrying duct system together so that the two ends can be joined and essentially sealed. 
   BACKGROUND OF THE INVENTION 
   This invention deals with an improved tool for providing a means for connecting the ends of a pair of sheet metal duct segments. There has been a need for a simple tool to bring together the ends of duct segments every since industry needed to convey air or pressurized fluids from one place to another. The ductwork joins a furnace or a HVAC system with various parts of a building to convey the warm air from the furnace to the various rooms or to convey HVAC air from and to various rooms. 
   The duct work cannot be formed in a single unitary section because of the need to work around corners, avoid piping of other sorts, walls, and the like and thus, duct work is provided in various segments of length. The segments must be joined together in order for the air to be conveyed thereby. The seams for such a joint must be tight in order to prevent the leakage of the air. 
   Duct systems are conventionally formed in sections and secured together to form longer spans as needed. A duct section is typically formed of sheet metal into a rectangular shape having four sides and bent or seamed corners at the intersection of the sides. A flange of some sort extends essentially perpendicularly outward from each side at both ends of the duct section. The sections are positioned end-to-end so the flanges of one section align with the flanges of the adjacent section and the aligned flanges are fastened together to form the duct assemblies. 
   When the ends of two duct segments, shown are  5  and  5 ′ in  FIG. 1A , are to be joined, they are brought together in close proximity and then various tools or devices are employed to finish the final adjustment to bring the pieces to together where they are finally joined by bolts, screws, connectors, and the like. 
   For this task, the ends of the duct segments are first formed into structures that will abide a fastener or connectors, and such a common joint  1  can be observed in  FIG. 2  of this disclosure. Shown in  FIG. 2  is a single bend of the sheet metal back onto itself, but it is common to strengthen the joint  1  by providing joints that have been doubly bent as is shown in  FIG. 1B . Further, there is shown in  FIG. 2 , a top view of a portion of a joint that has been formed by bringing the ends of two duct segments together, drawing them tight with a duct stretcher, and then sliding the connector  2  over the joined joints to hold them in place. Quite often, the connectors  2 , shown in  FIG. 3  have an end tab  4  on each end that is bent down onto the duct after the connector is put in place. 
   There are several tools in the prior art for tightening such joints and they are shown as a pincher type in  FIG. 4A , bar types with adjacent posts in  FIG. 4B , and a tool in  FIG. 4C  that is a double post with a moveable wheel, all of which have several disadvantages. One of the major advantages that these prior art tools share is the fact that they do not have any set-off feature, that is the capability of set off from the ductwork and thus, they are difficult to work with. 
   SUMMARY OF THE INVENTION 
   The present invention improves upon the devices or tools of the prior art by being easy and convenient to use, economically safe for the everyday user, and they are capable of exerting great pressure on the duct end pieces to pull them together without using undue strength. The unique feature of the tools of this invention having a first single pivot point, second double pivot points, and then a third single pivot point allows for the increased pressure created by the device, the pressure being creatable by the mere squeezing of the handles of the device. 
   THE INVENTION 
   Thus, this invention deals with a duct stretching tool wherein the tool comprises in combination two handles, each handle having a near end and a distal end and each near end has an inside surface. 
   Each near end of each handle has a set of laterally projecting tabs. The laterally projecting tabs are spaced from each other and each laterally projecting tab has a centered opening in it. The handles are joined at the laterally projecting tabs by a first pin inserted through the laterally projecting tab centered openings to form a first single pivot point. 
   The first pin has surmounted thereon a tension spring, that is, the tension spring encircles the pin. The tension spring has extended end segments and each extended end segment projects against a near end inside surface of a handle. 
   The near end of the handles has a set of forward projecting tabs wherein each of the forward projecting tabs has a centered opening in it. The forward projecting tab centered openings has a second pin through it to form a double pivot point. 
   There are two arms and each arm is attached to one of the handles at one of the double pivot points. The arm has a near end, a distal end, and a horizontal plane, each said arm having an inwardly extending tab near the arm near end wherein the inwardly extending tabs overlap. The overlapped inwardly extending tabs having a common opening through them and they have a common opening having a fastener through them to pivotally bind the arms together at a single pivot point. 
   Each first arm has a first continuing segment, each first continuing segment having a second continuing segment wherein the first and second continuing segments project in alignment with the first arm, the first continuing segment having a lower horizontal plane than the first arm and the second continuing segment having a lower horizontal plane than the first continuing segment, the distal end of the second continuing segment having an opening through it. 
   The distal end has a stirrup rotatably attached thereto by a pin inserted through each opening and each stirrup has a bottom bar, each bottom bar having a wheel attached thereto, each said wheel being rotatable relative to the stirrup. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a view in perspective of portions of two duct segments that are to be joined. 
       FIG. 1B  is a view in of a double bend at the end of the duct segment. 
       FIG. 2  is a view of a completed joint with the connector in place. 
       FIG. 3  is a front full view of a connector that is useful in ductwork. 
       FIG. 4A  is a pincer type of duct stretcher  40  of the prior art. 
       FIG. 4B  shows two bar types of duct stretchers  50  and  50 ′ of the prior art. 
       FIG. 4C  is a prior art duct stretcher  60  having two posts and one moveable wheel. 
       FIG. 5  is full top view of a device of this invention in the expanded or wide open position. 
       FIG. 6  is a full top view of a device of this invention in the closed and locked position. 
       FIG. 7  is a full side view of a device of this invention in which the arems and continuing segments are angled at 90°. 
       FIG. 8  is a full side view of a device of this invention that shows a sinuous configuration. 
       FIG. 9  is a portion of the distal end of the second continuing segment in which the wheel  30  is in an upward position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Turning now to a detailed description of the invention, there is shown in  FIG. 6  a full top view of a tool  6  of this invention in the compressed and locked position showing in combination, handles  7 , a first pivot point  8  comprised of overlapping tabs  21  on the handles  7 , a pin  22  inserted through openings  23  (not shown in this Figure), the distal ends  9  of the handles  7  showing a double pivot point  10  comprised of pins  25  through openings  26  ( FIG. 7 ), arms  11 , inwardly laterally extending tabs  12 , a pin  13  inserted in the opening  43 , for the tabs  12 , and a fastener  42 , that forms a second single pivot point  14 , and the second continuing segments  15  of the arms  11 . At the distal end  16  of the second continuing segment  15  there is shown the top edges  17  of stirrups  18  that are secured in a rotatable fashion to the distal end  16  by a pin  19 , inserted through opening  20  (shown in phantom). Also shown are the wheels  30 . 
   Turning now to  FIG. 7 , there is shown a full side view of a device  6  of this invention in which the components and parts not visible in  FIG. 6 , are clearly shown. For example, there is shown a pin  22  contained in opening  23  (shown in phantom) with a fastener  24  on the pin  23 . Also shown is a pin  25  through opening  26  (shown in phantom) and a fastener  27  for the pin  25 . 
   The first continuing arm segment  28  is shown in  FIG. 7 . In this Figure, it is shown as a right angled attachment, but it is within the scope of this invention to have an arm and continuing segments that are not angled, such as that shown in  FIG. 8 , which is a full side view of a device of this invention having a sinuous configuration. 
   In  FIG. 7 , there is shown the stirrups  18  that are fastened to lower bars  29  of the stirrups  18 . The wheels  30  are then attached to the lower bars  29  by any conventional means such that the wheels will rotate beneath the lower bars  29  in a circular motion. In addition, the stirrups  18  are fastened to the distal end  16  of the second continuing segment  15  by the use of the pins  19  such that the stirrups  18  rotate to allow the wheels to move from a lower position as shown in  FIG. 7  to an upper position as shown in  FIG. 9  (shown is a portion of the second continuing segment  15 ). 
   In  FIG. 6 , there is shown a conventional lock  31  which swings on a pin  25  that comprises part of the double pivot point  10 . This lock  31  is optional on this device. 
   It should be noted that for purposes of understanding of the invention, the arms  11  have been assigned a horizontal plane  41  as is shown in  FIG. 6 . The second continuing segments  15  have also been assigned a horizontal plane for purposes of understanding denominated  51  and shown by the dotted line in  FIG. 7 . The planes are shown in  FIG. 7  for comparison purposes, and for purposes of this invention, it should be noted that the horizontal planes of the second continuing segments  15  are below that of the planes of the arms  11 . That is so because in this manner, the tool  6  has a set off from the walls of the ducts that are being worked on and in this manner, the tool is more effective because the workman can fully grip the handles  7  of the tool  6 . 
   It should also be noted that the wheels  30  are made rotatable in the fashion described Supra so that the tool  6  can be used in tight spaces and around corners whereas the prior art tools cannot. Thus, the tools of this invention are highly versatile when it comes to their use. 
   The tools are manufactured from metals in order to retain the strength required for the end use. Preferred metals are aluminum, steel, stainless steel, and cast iron. Especially preferred are steel and aluminum, and mostly preferred is aluminum. 
   It is optional for the handles  7  of the device  6  to have coverings, such as rubber, plastic, and the like, in order to enhance the grip of an individual on the handles. It is also preferred to use a covering that is raised or has a rough surface so that the grip is enhanced. 
   The overall dimensions of the device  6  range from about 5 inches to about 14 inches long, and about 2 to about 5 inches in width at the greatest width of the device, so that they are amenable to the various circumstances of use. 
   The arms, and all continuing segments can be round, square, diamond, rectangular, and the like, in configuration. The size of the wheels  30  can be from about ½ inch to about 1 and ¼ inches in diameter, depending of the ductwork to be used. 
   It is contemplated within the scope of this invention that the continuing portions of the device  6  can be as cast or welded, or any other conventional means of construction as long as the necessary strength is employed in the materials and construction.