Abstract:
A pipe cutter is designed for cutting a pipe from the inside by insertion of the pipe cutter through an open end of the pipe. The pipe cutter includes an elongated hollow sleeve with first and second ends in which an elongated shaft which is longer than the hollow sleeve is located for rotation. One end of the elongated shaft is adapted for connection to a source of rotational power; and the lower or opposite end of the elongated shaft is attached to a rotary saw blade. A centering housing is located between the first and second ends of the hollow sleeve and includes a mechanism for moving the sleeve and the elongated shaft located in it from an initial position with the saw blade out of contact with the interior of the pipe to a position radially outward from the central axis of the pipe to engage and cut the pipe through a circular or orbital motion of the pipe cutter.

Description:
BACKGROUND 
   The field of the present invention relates to a tool for cutting the wall of a pipe from inside the pipe with insertion of the tool through an opening at one end of the pipe. 
   In the building construction industry, vertically extending pipes are used for connection to water supplies, sewer lines and the like, in regions where roadways and feeder lines to houses or industrial buildings under construction are provided. In addition, it is a common practice in the building industry for plumbers to install large diameter waste pipes and the like before the finished flooring has been installed. Such pipes may extend above the surface of the finished roadway or flooring, and subsequently must be cut to a selected length, either at the roadway or flooring surface or below that surface, for subsequent connection to other components in the construction process. 
   A variety of tools have been designed for the purpose of effecting the internal cutting of various types of pipe. In their simplest forms, such tools include an elongated shaft with a rotary saw blade on the end of it. The other end of the shaft then may be attached to a hand drill or the like. The saw blade is inserted into the pipe and is circularly rotated about the interior of the pipe until the pipe is cut off at the desired length. Variations of this technique have been provided by placing a circular plate at a desired distance above the saw blade on the shaft; so that the plate abuts the end of the pipe and determines the depth of the cut, while the entire apparatus is rotated or orbitally moved about the pipe end to allow the saw blade to cut through the pipe. 
   It is desirable to provide an improved internal pipe cutter for cutting pipes at a desired depth from the open end thereof in a simple and effective manner. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic representation of an operator using a pipe cutting tool according to an embodiment of the invention; 
       FIG. 2  is an exploded view of parts of an assembly of an embodiment of the invention; 
       FIG. 3  is a side view of the embodiment shown in  FIG. 2 ; 
       FIG. 4  is an exploded view of the embodiment shown in  FIGS. 1 and 2  with additional parts illustrated; 
       FIG. 5  is an assembled view of the embodiment shown in  FIG. 4 ; 
       FIG. 6  is a side view of the embodiment shown in  FIG. 5 ; 
       FIG. 7  is an overall partially exploded top perspective view of the embodiment of  FIGS. 1 through 6 ; 
       FIG. 8  is a top perspective view of the embodiment of  FIGS. 1 to 7  showing its manner of use; 
       FIG. 9  is a side view of the embodiment shown in  FIGS. 1 through 8  in a position of use; 
       FIG. 10  is a top perspective view of the embodiment of  FIGS. 1 through 9  illustrating an operative feature thereof; and 
       FIG. 11  is a side view of the embodiment of  FIGS. 1 through 10  showing its manner of use. 
   

   DETAILED DESCRIPTION 
   Reference now should be made to the drawings. In  FIG. 1 , an operator  40  is shown in conjunction with the operation of an embodiment of an internal pipe cutter  30 , which has been inserted into a pipe  32  extending above the surface of the ground  33 . The portions of the internal pipe cutter shown in  FIG. 1  include a hollow sleeve, through which an elongated rotating shaft  36  extends. The shaft  36  is driven by a source of rotational power, such as an air driven or electric driven drill  34 . A guide flange  38 , which has a diameter greater than the diameter of the pipe  32 , is attached to the sleeve for limited rotation with the sleeve to effect cutting of the pipe  32  in a manner explained more fully subsequently. The guide flange  38  establishes the depth of the cut, as is more fully explained subsequently. 
   Reference now should be made to  FIGS. 2 through 6 , which disclose the various features of a centering housing used in the embodiment of the invention disclosed. This centering housing includes bottom and top plates  50  and  70 , respectively, in the form of circular discs which have a diameter selected to be slightly less than the interior diameter of a pipe to be cut by the pipe cutter of the disclosed embodiment. The bottom and top plates  50  and  70  have elongated slots  60  and  80 , respectively, extending substantially from the center of each of these plates radially outwardly toward the outer circumference or edge of each of the plates  50  and  70 . 
   On opposite sides of the slots, a pair of spacers  52  and  54  for the plate  50 , and  72  and  74  for the plate  70 , are located parallel to and adjacent the respective slot  60  and  80 . The plates  52 , 54 , 72  and  74  serve as guide plates for upper and lower slide plates  94  and  90  (shown most clearly in  FIGS. 4 and 5 ). The channels for the slide plates  90  and  94  are formed on the lower circular housing plate  50  by a bar  56  on one side and a ratchet gear  58  on the other side, which extend inwardly toward the slot  60 , as shown most clearly in  FIG. 3 , to form a guide channel beneath them and between the facing edges of the plates  52  and  54 . Similarly, on the top circular plate  70  of the housing, a pair of elongated bars  76  and  78  are mounted on the guide plates  72  and  74  to form channels beneath their edges and the facing edges of the plates  72  and  74 , as shown most clearly in  FIGS. 3 and 6 . 
   The bottom and top plates  50  and  70  of the housing are held together and spaced from one another by means of three vertical posts  66 , which are extended between mounting holes  62  on the bottom plate  50  and  82  on the top plate  70 , as illustrated in FIGS.  3 , 4  and  6 . 
   Spacer wheels  110  are rotatably mounted on each of the posts  66 , and the outer edges of the wheels  110  extend slightly beyond the outer edges of the circumferences of the top and bottom plates  70  and  50  of the housing. Washers  112  and  114  (shown most clearly in  FIG. 6 ) space the wheels  110  a slight distance above the bottom plate  50  of the housing and a slight distance below the top plate  70  of the housing, as shown most clearly in  FIG. 6 . 
   The housing assembly is completed by a pair of slide plates  90  and  94  (mentioned previously), which are free to move reciprocally in a radial direction, as shown by the arrows in  FIG. 5 , back-and-forth in the channels formed by the guide plates  52 , 54 , 72 , 74 , the spacer bars  56 , 76 , 78 , and the rack gear  58 , as described previously. The spacing provided by the washers  112  and  114  is sufficient to allow the guide plates  90  and  94  to pass beneath the wheel  110  and over the wheel  110 , which is located diametrically opposite the slots  60  and  80 . 
   The slide plates  90  and  94  each have a circular opening in them in the position shown for the opening  92  in the slide plate  90  in  FIG. 5 . The circular opening in the plate  94  is not shown; but it is aligned with and is of the same size as the opening  92  in the top slide plate  90 . 
     FIGS. 7 through 11  should now be considered in conjunction with FIGS.  4 , 5  and  6  for additional details of the disclosed embodiment. An elongated hollow sleeve  140  is employed for supporting the centering housing, described above, and having the bottom plate  50  and top plate  70  defining its vertical thickness in conjunction with the spacers  66  and the washers  112  and  114  for the wheels  110 . This outer elongated hollow sleeve  140  has its lower end terminating in or extending slightly beyond a spur gear  100 A having an upward extending shoulder  100 B, as shown most clearly in  FIGS. 4 ,  6 , and  7 . The spur gear  100 A/ 100 B is braised onto, welded onto, or otherwise securely attached to the hollow sleeve  140 ; so that the sleeve  140  and the spur gear  100 A/ 100 B rotate together. 
   The outer sleeve  140  then carries a rotatable elongated drive shaft  146 , which has a length greater than the length of the hollow sleeve  140 . The shaft  146  may be journaled at the upper and lower ends of the sleeve  140  and at intermediate points, if necessary, by means of suitable bearings (not shown). Consequently, the shaft  146  is capable of free rotation within the sleeve  140  when the upper end of the shaft  146  (as depicted in  FIGS. 7 through 11  and  FIG. 1 ) is attached to a source of rotational power, such as the motor driven unit  34  depicted diagrammatically in  FIG. 1 . 
   As shown most clearly in FIGS.  7 , 9  and  11 , the lower end of the rotatable shaft  146  has a rotary saw blade  144  attached to it by any suitable means, such as a bolt or the like. As is apparent from an examination of  FIGS. 7 through 11 , the saw blade  144  extends a short distance below the bottom plate  50  of the centering housing. 
   As is apparent from  FIGS. 4 and 7  in particular, when the sleeve  140  is rotated counterclockwise (as viewed from the top), the spur gear  100 A/ 100 B also rotates with the sleeve  140  to which it is attached. This causes the relative position of the sleeve  140 , with respect to the plates  50  and  70 , to move from the generally centered location depicted in  FIGS. 4 and 7 , to an offset location depicted in  FIG. 10 . The length of the slots  60  and  80  in the plates  50  and  70 , respectively, determines the maximum displacement which can take place, as shown in  FIG. 10 . When the sleeve  140  is rotated in a clockwise direction (as viewed from the top in  FIGS. 7 through 11 ), movement of the sleeve  140 , relative to the plates  50  and  70 , is in the opposite direction toward the center to the position shown in  FIG. 7 , which depicts the maximum movement in this direction for the relative displacements of the centering housing and the outer sleeve  140 . 
   The structure of the saw embodiment which is disclosed in the drawings is completed by the inclusion of a vertically adjustable guide flange  150 , which is slidably mounted on the hollow sleeve  140  for movement up and down on the sleeve, as shown by the double-ended arrow A in  FIG. 8 . The outer diameter of the guide flange  150  is selected to be greater than the outer diameter of the pipe  160  ( FIG. 8 ) with which the internal pipe cutter is to be used. The vertical adjustment of the flange  150  on the outer sleeve  140  is selected to cause the position of the saw blade  144  ( FIG. 9 ) to be at the desired level for effecting the cut. Once the distance between the blade  144  and the underside of the guide flange  150  for the desired depth of cut has been determined, the guide flange  150  is secured by means of a set screw  154  through a shoulder  152  attached to the guide flange  150  to releasably hold the guide flange in place on the sleeve  140  to cause the saw blade  144  to be at the desired depth. 
   Once the apparatus has been inserted into a pipe  160  as shown in  FIG. 9 , the relative position of the various parts are as indicated. The source of power for the rotational drive shaft  140  is engaged to spin the saw blade  144 . Then the outer sleeve  140  is rotated counterclockwise (as described previously) to move the saw blade  144  from the relatively centered position in  FIG. 9  to the offset positions shown in  FIGS. 10 and 11 . Once the saw blade  144  engages the interior diameter of the pipe  160 , the force between the saw blade  144  and the housing  50 / 70  through the spur gear  100 A and ratchet gear  58  ( 100 A/ 100 B) tends to force the centering housing  50 / 70  in the opposite direction against the inside of the pipe where the wheels  110  engage the pipe interior. Once the saw blade  144  has been moved radially outwardly to a position where it cuts through the pipe  160 , the entire assembly is orbitally or circularly rotated to allow the blade  144  to complete a circular cut in the pipe  160 . 
   The centering housing  50 / 70  and its internal components allow a cut by the blade  144  to be perpendicular to the central axis of the pipe  160  and the central axis of the hollow sleeve  140 , as is readily apparent from an examination of  FIG. 11 , for example. 
   Once the cut has been completed, the outer sleeve  140  is rotated in a clockwise direction (again, as viewed from the top in the various figures) to cause the spur gear  100 A/ 100 B to move the hollow sleeve  140  radially inwardly back to the position shown in FIGS.  7 , 8  and  9 . Once this has been accomplished, the saw can be removed by lifting it vertically out of the pipe; and the cutoff portion of the pipe  160  then can be removed. 
   The internal pipe cutter described above in conjunction with the embodiment shown in  FIGS. 1 through 11  provides a relatively stress free operation for the operator utilizing the pipe cutter; and by means of the centering housing facilitates accurate placement of the pipe cutter within the pipe and maintains the desired relationship between the offset position of the saw blade  144  and the centering housing  50 / 70  throughout the duration of the cut being made. 
   The foregoing description of an embodiment of the invention is to be considered as illustrative and not as limiting. Various changes and modifications will occur to those skilled in the art to achieve substantially the same result, in substantially the same way without departing from the true scope of the invention as defined in the appended claims.