Abstract:
A tool for cutting a plastic pipe comprising a concave guide section having a central aperture; and a plunger having a longitudinal axis extending through the central aperture and at least one blade extending in generally radial relation from the central axis inside the concave guide section.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to cutting articles by use of a rotating axially moving tool and more particularly to cutting tools having a work-engaging structure and angled or stepped cutting edges. Still more particularly, the present invention relates to cutting plastic pipe to enable a lateral pipe to be replaced on a Y-connection, a T-connection or a 90° connection. 
     2. Background Information 
     The prior art discloses various tools and methods for cutting pipe. 
     U.S. Pat. No. 3,752,592 to Fitzgerald, et al., for example, discloses a pipe reamer apparatus particularly for use with plastic pipe and a method of reaming plastic pipe fittings such as elbows or the like. 
     U.S. Pat. No. 3,872,748 to Bjalme, el al. discloses a tool for beveling plastic pipe in which the tool is carried in a slide inclined at the bevel angle and fed toward the pipe end as it is rotated about the axis of the pipe. 
     U.S. Pat. No. 4,483,222 to Davis discloses a device for removing pipe attached to a fitting includes cutting apparatus for removing the pipe disposed within the fitting. A wrench apparatus is connected to the cutting apparatus for gripping the fitting to prevent its movement when the cutting apparatus is activated. Alternatively, this device may be used as a reaming device which permits radial movement of the cutting blades into engagement with a pipe after the cutting blades have been inserted within the pipe. 
     U.S. Pat. No. 4,693,643 to Heyworth discloses a planing device which is operable for progressively planing or cutting the end of a plastic pipe to the desired length, or for reaming out a piece of plastic pipe fixed in a plastic pipe fitting in such a manner that the plastic pipe fitting can be reused. The pipe planing device is portable and is rotated by an electric drill or the like and includes a cylindrical pilot removably supported on radially spaced-apart spider-like cutter arms having cutter blades attached to their outer ends and extending outwardly beyond the cylindrical pilot distance which is equal to the thickness of the plastic pipe to be cut or reamed. The outer circumference of the cylindrical pilot is dimensioned to provide a snug rotatable fit within the end of the plastic pipe to be planed and operates to center the planing device along the longitudinal axis of the plastic pipe. 
     U.S. Pat. No. 4,975,001 to Rabo, et al. discloses a plastic pipe reboring tool having an elongated shank, a generally concave-convex cutting head, and changeable guide discs effective for cleaning residue glue and plastic from used plastic pipe and fittings so they can be used over again. The reboring tool is operational with both powered and manual chuck rotating devices and can be used on different sizes of plastic pipe. 
     U.S. Pat. No. 5,000,629 to Nygards discloses a self-centering plastic pipe router tool for routing of a sawed-off end of pipe from the interior surface of a salvageable pipe. The router tool is a disk with an axial shank on one side of the disk. A pair of cutting flanges extend radially outwardly and upwardly in the direction of the axial shank form the disk perimeter to form first and second cutting edges. A concentric cylindrical skirt extends downwardly form the disk for axial centering of the router tool within the waste pipe inner diameter. The first cutting edges are sized for routing of the waste pipe and second cutting edges are sized to plane and refinish the interior surface of the salvageable pipe for re-use. 
     U.S. Pat. No. 5,401,126 to Norris, et al. discloses a bit usable in combination with a rotatory diver, such as a drill, for extracting a remnant of a cut-off pipe from a pipe socket. The bit comprises a forward portion which is a pilot to keep the bit centered in the remnant and thereby centered in the pipe socket, a forward-facing ring cutter whose inner and outer diameters generally match the inner and out diameters of the pipe remnant being extracted, said ring cutter bing operable to cut and/or scrape the remnant edgewise form the socket, and a forward facing ring scraper operable to stop the bit from excessive penetration into the pipe socket and operable to scrape bonding material remnants form the end face of the pipe coupling. 
     In working with plastic pipe, a relatively common procedure involves replacing a lateral line which extends at a Y-connection, a T-connection or 90° connection at a at a main pipe line. This procedure is relatively time and labor intensive and an improved means of carrying this procedure out is needed. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved apparatus and method for replacing a lateral line which extends from a Y-connection, a T-connection or a 90° connection at a main pipe line. 
     This and other objects are met by the present invention which is a tool for cutting a plastic pipe comprising a concave guide section having a central aperture. A plunger having a longitudinal axis extends through the central aperture and at least one blade extends in generally radial relation from the central axis inside the lower concave skirt section. 
     In another embodiment the present invention is a tool for cutting a plastic pipe comprising a concave guide section comprising a lower skirt comprising an upper generally horizontal member and a lower peripheral wall member. There is an aperture in said upper horizontal member and a tubular section having an upper and a lower terminal end and an interior axial passageway and is positioned at said lower terminal end such that said axial passageway is aligned with the central aperture of the generally horizontal member of the lower skirt section. A plunger comprising an upper rod having an upper and a lower terminal end and a spiring retaining structure adjacent said upper terminal end and is disposed in said axial passageway of the tubular member of the concave guide section in coaxial relation with said tubular member and is positioned such that said upper terminal end is elevated above the upper terminal end of the tubular member. A lower blade retaining structure is formed in which at least one blade having a distal edge extends in a generally radial direction such that said distal edge is positioned in spaced inward relation from the lower peripheral wall member of the concave guide section. A helical spring having an upper terminal end and a lower terminal end and coaxially overlaps the upper rod member and bears against the spring returning structure of the rod member at its upper end and bears against the upper terminal end of tubular member at its lower end. 
     Also encompassed by the present invention is a method for replacing a first lateral pipe with a second lateral pipe when the first lateral pipe is connected to a main pipe line by a Y-connection, a T-connection or a 90° connection. In this method the first lateral pipe is cut outwardly from the widened connection socket on the Y-connection, a T-connection or a 90° connection. A tool as is described above is then positioned reality to the widened connection section so that the inner surface of the concave guide section bears against the outer surface of widened lateral connecting section and distal edge of the blade bears against the first lateral pipe section. The plunger is then rotated about it longitudinal axis so that the blade cuts away at least part of the inner first lateral pipe section to form a pipe receiving space adjacent the widened connection socket. A second lateral pipe is then inserted end wise into the pipe receiving space to complete the procedure. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is further described with the reference to the accompanying drawings in which: 
     FIG. 1 is a cut-away front elevational view of a preferred embodiment of the pipe cutting tool of the present invention; 
     FIG. 2 is a bottom plan view of the pipe cutting tool shown in FIG. 1; 
     FIG. 3 is a schematic view of a lateral line extending from a main line in which illustrates a first step in a preferred embodiment of the method of the present invention; 
     FIG. 4 shows the pipe arrangement shown in FIG. 3 after attachment of the cutting tool shown in FIG. 1 to illustrate further steps in the preferred embodiment of the method of the present invention; 
     FIG. 5 is a bottom and front perspective view of a bit which may be used in an alternate embodiment of the cutting tool of the present invention; 
     FIG. 6 is a bottom and front perspective view of a guide section which may be used with the bit shown in FIG. 5 in an alternate embodiment of the cutting tool of the present invention; 
     FIG. 7 is a vertical cross-sectional view of an alternate embodiment of the cutting tool of the present invention using the bit shown in FIG.  6  and also show in conjunction with a Y-connection to illustrate a step in the method of the present invention; 
     FIG. 8 is a vertical cross-sectional view of the cutting tool shown in FIG. 7 in use on a Y-connection to show further steps in the method of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIGS. 1 and 2, the cutting tool of the present invention includes a guide section  10  which is made up of a tubular section  12  which has an upper terminal end  14  and a lower terminal end  16  and an axial bore  18 . The guide section  10  also includes a lower skirt section  20  which has a horizontal top  22  made up of radial support members  24 ,  26  and  28  with a central aperture  30 . 
     The lower skirt section  20  also includes a peripheral wall member  32  which has an inner side  34  and an outer side  36  with a plurality of apertures as at aperture  38  in this peripheral wall member  32  which allows operation of the tool to be monitored. The cutting tool also includes a plunger section  40  which has an upper rod  42  having a longitudinal axis  44  and an upper terminal end  46  and lower terminal end  48 . A pin  50  and washer  52  serve as a retaining member for a helical spring  54 , which is also retained at its lower end by the upper terminal end  14  of tubular member  12  of the guide section  10 . The plunger section  40  also includes a lower central blade support structure  56  from which blades as at blades  58 ,  60  and  62  extend radially. These blades have respectively wedge shaped terminal cutting edges  64 ,  66  and  68 . Blades  58  and  62  also have respectively upper outwardly extending steps  70  and  71 . 
     Referring to FIGS. 3 and 4, the method of using the tool described above to replace a lateral pipe extending from a Y-connection or T-connection is described. In these figures there is a Y-connection  76  with a horizontal section  78  having at its opposed ends widened pipe sockets  80  and  82 . Main line pipes  84  and  86  are connected respectively to the Y-connection  76  at the widened pipe sockets  80  and  82 . The Y-connection  76  also includes a lateral section  88  which has a terminal widened pipe socket  90 . A lateral pipe  92  is connected endwise to this widened pipe socket  90  and extends outwardly therefrom. In the first step of the method of this invention the lateral pipe  92  is cut slightly outwardly from the pipe socket  90  as is shown particularly in FIG.  3 . Lateral pipe  92  is thereby divided into an inner lateral pipe section  94  which remains attached to the pipe socket  90  and an outer pipe lateral pipe section  96  which is removed. As is shown particularly in FIG. 4, in the next step of the method the tool shown in FIGS. 1 and 2 is positioned on the Y-connection  76  so that the blade edges as at  64 ,  66  and  68  bear against the inner lateral pipe section  94  and the inner side  34  of the peripheral wall member  32  bears against the pipe socket  90 . The upper rod  42  of the plunger section  40  is then rotated about its longitudinal axis  44  so that the blades cut or abraid the inner lateral pipe section  94  until some or all of the pipe section  94  is removed so that a pipe receiving space is formed adjacent the pipe socket  90 . A new lateral pipe  92  is then inserted endwise into the pipe socket  90  to finalize the procedure. 
     Referring to FIG. 5, there is shown a bit  98  which may be used in an alternate embodiment of the pipe cutter of the present invention. This bit  98  includes blades  100 ,  102 ,  104 ,  106 ,  108  and  110 . The bit  98  also includes a threaded bore  112  to allow attachment to a rod (not shown) similar to the one shown in FIG.  1  and described above. Each blade as, for example, blade  100  includes a lower section  114  which has a cutting edge  116 . There is also a lower step cutting edge  118  and an upper section  120  with a cutting edge  122 . Above cutting edge  122  there is an upper step cutting edge  123 . 
     Referring to FIG. 6, a guide section  124  which may be used in an alternative preferred embodiment is shown. This guide section  124  has a tubular member  126  with an axial bore  128  and a concave section  130 . This concave section  130  comprises a horizontal member  132  with a central aperture  134  and is connected by vertical supports  136 ,  138  and a  140  to a lower skirt member  142 . 
     Referring to FIGS. 7 and 8, the method of use of the alternative preferred embodiment using the bit  98  shown in FIG.  5  and guide section  124  shown in FIG. 6 is illustrated. Here there is a Y-connection  143  similar to the structure described in FIGS. 3 and 4 which has a lateral section  144  with a widened pipe socket  146 . The first section of lateral pipe  148  which remains after the pipe has been cut in the way described above is fixed endwise in the widened pipe socket  146 . The alternate embodiment of the cutter is shown in FIG. 7 in an initial position axially aligned with widened pipe socket  146  and the first section of lateral pipe  148 . It will be observed that in addition to the features described above in the bit  98  and guide section  124  the tool has a plunger  158  which includes the rod  160  which is fitted with the threaded bore of the bit  98 . In this position a pin  154  which extends through apertures in the tubular section  126  and rod  160  holds the bit  98  in an upper position in the guide section  124  adjacent the horizontal member  132 . After the pin  154  is removed the rod  160  along with the bit  98  is moved forward to engage the first section of the lateral pipe with the blades as at blade  100  at the same time the skirt  142  outwardly engages the widened pipe socket  146 . The rod  160  is rotated about its longitudinal axis so that the blades as at blade  100  cut or abraid the first section of lateral pipe  148  to allow its removal, thus leaving a pipe receiving space adjacent the pipe socket  146 . In particular, it will be seen from FIG. 7 that pipe  148  is cut by cutting edges  116  and  118 . The tool is then removed from the widened pipe socket to allow a second lateral pipe (not shown) to be inserted endwise into the widened pipe socket  146 . It will also be appreciated that it would be possible to increase the inner diameter of a pipe. For example, it will be seen from FIG. 8 that the inner diameter of pipe socket  146  could be increased by means of cutting edge  123  with support being provided by cutting edge  122 . 
     Those skilled in the art will appreciate that the tool and method of its use described above on a Y-connection can easily be adapted to replace a lateral pipe connected to a T-connection or a 90° connection. 
     It will be appreciated that a tool and the method of its use has been described which allows for the efficient, quick and cost effective removal of a lateral pipe on a Y-connection, a T-connection or a 90° connection and its replacement with another lateral pipe to that connection. 
     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.