Abstract:
A pipe cutting supplemental apparatus and method prevents thin-walled pipe from collapsing when being cut with a standard pinch roll cutter. The tool may be embodied as a solid cylindrical insert, or a hollow cylindrical sleeve, or an expandable, segmented body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 11/316,434 filed on Dec. 22, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention is in the field of pipe cutting, particularly in cutting plastic pipe, most particularly polyvinyl chloride pipe.  
         [0004]     2. Background of the Invention  
         [0005]     Polyvinyl chloride pipe comes in a variety of dimensions and is representative of the class of plastic pipe. Plastic plumbing pipe is less expensive than metal pipe and has come into common usage for that reason. However, plastic pipe in general and certain dimensions of PVC in particular are also weaker than metal pipe.  
         [0006]     It remains the convention in the plumbing field for pipe to be cut with pinch roll cutters. These familiar cutters have a circular blade mounted to form one side of a vise type of holder for the pipe. The other side of the vise type gap into which the pipe is placed for cutting includes an extendable holder for the pipe. In operation, the pipe is placed in the pipe cutter in the gap between the holder and the blade and the holder is advanced by the plumber turning a screw fitting until the holder is carried into contact the pipe. The pipe and pipe cutter are then rotated relative to one another so that the circular blade may roll around the entire circumference of the pipe, cutting it to a first depth. Thereafter, the plumber tightens the screw fitting to press blade further into the pipe and rotates the pipe cutter and pipe relative to one another again. This process repeats until the pipe is cut. These pinch roll cutters produce straight smooth cuts of metal pipes that are desirable for the tight liquid seals they create and the ease with which they may be worked. The pinch roll cutter is ideal for a pipe that is sufficiently rigid to withstand the pressure of the advancing screw equipment.  
         [0007]     An alternative cutting method for the pipe in general, but more particularly softer plastic pipe, is to simply saw the pipe with a saw blade such as a hack saw. The advantage of this approach is that softer and less rigid materials may be cut without deforming them. The disadvantage is that uneven, rough cuts are generally more difficult to work with and undesirable shavings are also generated.  
         [0008]     Unfortunately, some of the dimensions of plastic plumbing in common usage today, including PVC pipe, are thin-walled enough that the use of the preferred pinch roll cutter is impossible. One and one-half inch, one and one-quarter inch and narrower dimensions of plastic pipe in general, and PVC in particular, are too thin-walled to maintain their cylindrical shape in a pinch roll cutter that is screwed tightly enough to cut the pipe. Instead, these pipes crimp, crack or collapse before a cut can be completed. Since the alternative of sawing them is also undesirable for the reasons stated, there is a need in the art for a tool and method of cutting the smaller dimensions of plastic pipe in order to finish with a clean cut. There is a need in the art for a tool to supplement the plastic pinch roll cutter for cutting small dimensions of plastic pipe. Also, if the walls of metal pipe are thin enough, there is a need for a tool to prevent crimping and collapse for them as well. As always, there is a continuing need in the art for economy, durability, ease of manufacturing and ease of use of such tools.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention is a rigid support to be used in conjunction with a pinch roll pipe cutter. In a first embodiment, the tool is a solid cylinder dimensioned to be inserted within standard diameters of plastic pipe and with a sufficient tolerance to support the plastic pipe walls and to maintain their cylindrical shape from the inside as the pipe is cut from the outside with the pinch roll cutter.  
         [0010]     In another embodiment, the tool is itself a cylinder having an inside dimension corresponding within a given tolerance to the outside dimension of the standard dimensions of thin-walled plastic pipe in common usage. The cylindrical outer tool has a window through which the circular blade of the pinch roller may be advanced against the outer wall of the pipe to be cut. The inner wall of the cylindrical tool provides the necessary support to prevent collapse of the pipe being cut.  
         [0011]     In yet another embodiment, the tool comprises a substantially cylindrical expandable body portion that is expanded and contracted by changing the position of two end members. The two end members are substantially conical in shape, and a threaded shaft passes through the center of both end members and the body portion. As the conical end members are drawn together an inner surface of the body portion comes into contact with the increasingly large diameter of the end members, forcing the body portion to expand. Conversely, as the end members are drawn apart from each other the body portion is retracted by elastic bands. A nut is used at the distal end of each end member to achieve and maintain a desired diameter of the expandable body portion.  
         [0012]     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0014]      FIG. 1  is a perspective view of the first embodiment of the present invention.  
         [0015]      FIG. 2  is a perspective view of the second embodiment of the present invention.  
         [0016]      FIG. 3  is a perspective view of an alternative embodiment of the present invention.  
         [0017]      FIG. 4  is a perspective view of an alternative embodiment of the present invention.  
         [0018]      FIG. 5  is a perspective view of an alternative embodiment of the present invention.  
         [0019]      FIG. 6  is a plan view of an alternative embodiment of the present invention.  
         [0020]      FIG. 7  is a plan view of an alternative embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
         [0022]     Referring now to the drawings in which like reference numerals refer to like elements,  FIG. 1  depicts a solid cylindrical pipe cutting insert according to the present invention. The insert  10  includes a first end  12  and a second end  14 , each having different outside diameters. The tool may be of varying length. The first diameter  16  and second diameter  18  would each be a diameter corresponding to a standard inside diameter of plastic piping, in common usage, particularly including polyvinyl chloride (PVC) pipe. The insert  10  may be made of any rigid material, including without limitation plastic or metal.  
         [0023]     For example, one and one-half inch PVC pipe in actuality has an outside diameter of approximately 1.480 inches. Such pipe in common usage typically has a wall thickness of 0.070 inches. Accordingly, subtracting both walls, the inner diameter is 1.340 inches. Hence, the dimension  18  of portion  14  illustrated in  FIG. 1  would be substantially about 1.340 inches in diameter. Diameter  18  could actually be smaller to a certain tolerance and remain within the scope of the present invention.  
         [0024]     Similarly, one and one-quarter inch PVC pipe has an outside diameter of 1.250 inches. Allowing for a wall thickness that is also 0.070 inches, the inner diameter is 1.110 inches. Accordingly, diameter  16  of portion  12  of the insert is substantially about 1.110 inches and may be smaller within a given tolerance. Other types of plastic and even metal pipe may include walls thin enough to collapse under the pressure of a standard pinch roll cutter. For example, one and one-half inch 20-gauge pipe having an outside diameter of 1.5 inches and a wall thickness of 0.020 inches would have an inside diameter of 1.460 inches. Accordingly, an insert  10  made according to the present invention would have an outside diameter of substantially 1.460 inches and could be smaller within a certain tolerance. Similarly, one and one-quarter inch 20-gauge pipe having an outside diameter of 1.25 inches and a wall thickness of 0.020 inches would have an inside diameter of 1.210 inches. Accordingly, a dimension  16  of insert  10  may have an outside diameter of 1.210 inches or slightly smaller than a certain tolerance.  
         [0025]     In operation, a plumber inserts the appropriate end, either  12  or  14  inside the pipe to be cut. Thereafter, the pinch roll cutter is applied to the outside of the pipe at a position on the pipe corresponding to the location of the insert on the inside. Pinch roll cutting proceeds as usual, with the plumber tightening the screw head to advance the pipe holder against the pipe and thus apply pressure against the pipe forcing it into the circular cutter blade. With the insert  10  of the present invention installed within the pipe, the thin pipe walls, as they begin to tend towards collapse, come into contact with the outside dimension of the insert and are supported by it. Accordingly, cutting of the pipe wall advances without the pipe loosing its desired cylindrical shape because that shape is maintained by the cylindrical outside diameter of the insert.  
         [0026]     The tolerances referred to may vary. The tolerances need only be sufficient to maintain substantially cylindrical shape of the pipe being cut and to prevent cracking, crimping or collapsing of it. The particular material and wall thickness of the pipe may affect the allowable tolerance. For example, a tolerance of about 0.005 would correspond to one and one-half inch PVC.  
         [0027]     A second embodiment of the present invention is depicted in  FIG. 2 . A cylindrical sleeve  50  is shown having an inside diameter  52  and a window  54 . The inside diameter  52  of sleeve  50  is dimensioned to correspond to the outside diameter of standard sizes of thin-walled pipe in modern usage, including plastic, particularly PVC but also including thin-walled metal pipe. The window  54  is dimensioned to operatively receive the circular blade of the pinch roll cutter. The rest of the circumference of sleeve  50  is solid. Opposite window  54  the solid outside of sleeve  50  may receive the holding and cutting pressure of the screw mount holder of the standard pinch roll cutter.  
         [0028]     In operation, the pipe to be cut is inserted into sleeve  50  and advanced until the place that is to be cut appears in window  54 . Thereafter the pinch roll cutter circular blade is inserted from the outside through window  54  and the sleeve  50  is placed in the opening of the pinch roll cutter. The pipe holder is applied against the opposite solid side of sleeve  50  and the pinch roll cutter is used in the standard fashion. The pipe being cut is rotated within the internal diameter  52  of sleeve  50 . Pressure is applied to the pipe between the circular blade of the pinch roll cutter through window  54  and the opposite inside wall of sleeve  50 . The pipe is prevented from crimping or collapsing by the circumferential rigid support of inside diameter  52  of sleeve  50  and the close contact of it with the pipe&#39;s outside diameter.  
         [0029]     It is within the scope of the present invention that the insert of the embodiment depicted in  FIG. 1  and the sleeve depicted in  FIG. 2  may come in any dimensions. It is anticipated that a series of inserts or sleeves will be made, sold and used together as a tool kit, similar to the variously sized crescent wrenches commonly found in tool kits.  
         [0030]      FIG. 3  is a perspective view of an alternative version of the present invention. This alternative includes annular detents  130  and  132 . These features are located and dimensioned such that a pipe will still be adequately supported during cutting with a pinch roll cutter, while the indentations or recesses  130  and  132  provide a space into which the blade of the pinch roll cutter may be turned without being dulled by contact with the outer dimension of elements  112  or  114 . Also depicted in  FIG. 3  is a series of hash marks  134  which may be used by the plumber to measure the distance from the end of the tool to the end of the pipe, to assist the plumber in ensuring that his cut is located at a proper distance from the end for support by the tool and/or that his cut is a proper distance from the end of the pipe to align the blade of the pinch roll cutter with one of the annular detents  130  or  132 .  
         [0031]      FIG. 4  depicts a similar feature, which is assembly  240  designed to extend on the outside of the pipe being cut and also to indicate a distance into the pipe that the tool extends. Accordingly, assembly  240  is comprised of a longitudinal element  242 . This element may have upon it hash marks  244  for measuring a distance along the length of the pipe being cut. The longitudinal element  242  may be mounted on a post  246 . The post may swivel in order that the longitudinal element may be used in conjunction with either of elements  212  or  214 . The post  246  is mounted on an abutment  248 , which may also be used as a stop to hold a work piece.  
         [0032]      FIG. 5  depicts an alternative embodiment of the present invention having an additional extension  316 . Additional extension  316  has an outside diameter  320  which is dimensioned to coincide with the inside diameter of another size of pipe in common use. For example, dimension  320 , the outside diameter of extension  316 , may equal the inside diameter of a 2 inch pipe. The extension  316  also has an interior diameter  322 . This diameter is dimensioned to coincide with the outside diameter of element  312  of the tool. Accordingly, extension  316  may be slipped over element  312  and maintained there for storage and/or end use. In operation, use of extension  316  is substantially identical to the operation of element  312  or  314 .  
         [0033]      FIGS. 6 and 7  depict yet another alternative embodiment of the present invention, which is substantially comprised of an expandable body portion  410 , a threaded shaft  420 , and two substantially conical end members  430 . In the depicted embodiment the body portion  410  is substantially cylindrical and is coaxial with the shaft  420  and the two conical end members  430 . The body portion  410  has an annular cross-section having an inside diameter  442  and an outside diameter  444 . In the depicted embodiment, the body portion  410  is comprised of a plurality of independent segments  412 , (three are visible in  FIG. 6 ; two in  FIG. 7 ) which are separated by gaps  414  that run axially along the body portion  410 . The independent segments  412  are held together by one or more retention members, which in the depicted embodiment are elastic straps  450 . Each elastic strap  450  is seated in a seat  416  that runs annularly around the body portion  410 . In the depicted embodiment, there are four circumferentially spaced longitudinal segments. The outer circumference of each is rounded to comprise a circle when retracted to its smallest diameter. When expanded to larger diameters the cross section becomes increasingly square as it is expanded. Surprisingly, sufficient supporting contact to advantageously resist deformation while cutting copper and PVC pipes is maintained by only three segments maintaining at least three contact points with the pipe, when having a starting diameter of at least 20 mm, preferably 25 mm.  
         [0034]     In the depicted embodiment the end members  430  have a conical portion  432  that is oriented with the narrower diameter inward. The conical portion  432  tapers from a diameter slightly larger than the diameter of the threaded shaft  420  to a maximum diameter farthest from the center of the device. The end members  430  are situated on the shaft  410  on both sides of the body portion  410  such that their bases face the distal ends of the shaft  410 . A wing nut  434  is utilized behind each end member  430  to hold the end members  430  at a desired position on the shaft  420 . Preferably, a washer  436  is placed between the wing nut  434  and the end member  430 .  
         [0035]      FIG. 6  illustrates the depicted embodiment where the inside diameter  442  and the outside diameter  444  are at a minimum. As the end members  430  are brought together, they contact the body portion  410  and exert a radial force on the inner surface  418  of the body portion  410  causing the body portion  410  to expand and the inner diameter  442  and outer diameter  444  to increase. Conversely, as the end members  430  are moved apart from each other the body portion  410  retracts because the segments  412  are biased radially inwards by the retention members, bands  450 . Consequently, the inner diameter  442  and outer diameter  444  decrease.  FIG. 7  illustrates the depicted embodiment where the inside diameter  442  and the outside diameter  444  are increased. In the depicted embodiment the expansion of the body portion  410  is effected by a widening of the gaps  414  between the individual segments  412 .  
         [0036]     The outer surface of the expansion body is designed to support the pipe being cut while also receiving the blade of the pipe cutter. The outer surface  460  has a series of annular grooves (topside of  FIGS. 6 and 7 ) or serrations (bottom side) axially spaced along its length. The concavities of the serrations or the grooves will receive a blade of a pipe cutter in order that the blade not be blunted against a smooth surface expansion body. The convexities between the grooves will continue in contact with the inner diameter of the pipe being cut and support it against deformation. The width of the grooves or serrations is dimensioned to provide deformation resistant support for copper or PVC pipes. In the depicted embodiment the grooves are about 1.0 to 2.0 mm wide, and are axially separated by about 0.25 to 1.0 mm, they are about 0.5 to 1.5 mm deep. The expansion body may be made of relatively soft material, such as plastic or hard rubber.  
         [0037]     The outside diameter  444  may be adjusted to be substantially equivalent to an inside diameter of a pipe being cut. The tool is inserted into a pipe to support the pipe walls during the cutting process. This embodiment allows the tool to be used to support the cutting of pipes of various diameters. This embodiment may also be utilized together with the various innovations of the other embodiments found herein to increase the effectiveness of the tool.  
         [0038]     As various modifications could be made to the exemplary embodiments, as described above with reference to the corresponding illustrations, without departing from the scope of the invention, it is intended that all matter contained in the foregoing description and shown in the accompanying drawings shall be interpreted as illustrative rather than limiting. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims appended hereto and their equivalents.