Patent Publication Number: US-6658738-B1

Title: Pipe and tubing cutter

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a cutter for use in cutting a range of different diameter plastic pipe and tubing. It will be understood that the utility of the cutter is not limited to “plastic” or to “pipe or tubing”, those terms being used in a non-limiting sense to indicate the type of material to be cut not necessarily the identity of the material such that the term “cutter” as used in the subjoined patent claims also includes without limitation a cutter for rubber extrusions and the like. 
     2. Brief Description of the Prior Art 
     A cutting tool for cutting plastic pipe and tubing is described in U.S. Pat. No. 4,336,652 to Robertson. The cutter described in this patent is commercially available. For best cutting action, a knife blade should make an angle of about forty-five degrees with respect to the plastic pipe or tubing at initial contact. Since the pivot point of the Robertson cutter is fixed, this can be achieved with different diameter pipe and tubing only by offering the cutter in different sizes. It would be desirable to have a cutter adapted for cutting a range of different diameter plastic pipe and tubing. 
     The jaw members of a Robertson-style cutter are pivoted open by raking the handle end of the jaw bearing the knife blade across the user&#39;s clothing or body. In cutters dimensioned for use in cutting larger diameter pipe and tubing, the knife blade tends to flex making it very difficult or impossible to make a square cut. Other shortcomings of the Robertson cutter include a two-part construction of the jaw with the knife blade. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to provide a cutter which can be used with a range of different diameter plastic pipe and tubing. It is another object to provide a cutter which minimizes blade flexing for a square cut. It is also an object to provide a cutter wherein the angle of initial contact between the knife and the pipe or tubing approaches optimal for commonly available sizes of pipe or tubing. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter. 
     In accordance with the invention, a cutter for cutting a range of different diameter plastic pipe and tubing has a pair of jaw members pivotally connected intermediate their ends. A first of the jaw members is pivoted on a pivot pin within a second of the jaw members. The first jaw member has a handle at one end and a knife blade extending from the other end. The knife blade has a longitudinal cutting edge. The other of the jaw members has a handle at one end and a cradle with a generally semi-circular cutting cage at the other end into which the knife blade extends. The pivot pin is longitudinally adjustable in the second jaw member for changing the pivot axis of the first jaw member thereby changing the effective cutting cage of the cradle and the angle at which the cutting edge of the knife blade makes on initial contact with the pipe and tubing. 
     The invention summarized above comprises the constructions hereinafter described, the scope of the invention being indicated by the subjoined claims. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated, corresponding reference characters refer to corresponding parts throughout the several views of the drawings in which: 
     FIG. 1 is an exploded view of a pipe and tubing cutter in accordance with the present invention; 
     FIG. 2 is a side elevation of the cutter with a first jaw member pivoted within a second jaw member; 
     FIG. 3 is a side elevation of the cutter shown cutting a small diameter pipe or tubing with a pivot pin in the forwardmost position and the cutting edge of the knife blade making an angle of about forty-five degrees with respect to the pipe or tube on initial contact; 
     FIG. 4 is a side elevation of the cutter shown cutting a medium diameter pipe or tubing with the pivot pin an intermediate position; 
     FIG. 5 is a side elevation of the cutter shown cutting a large diameter pipe or tubing with the pivot pin in the rearwardmost position; 
     FIG. 6 is detail partly in section taken along plane  6 — 6  in FIG.  9  and showing a pivot pin with a shaft and first and second heads, with the shaft received in corresponding cavities on opposite sides of the second jaw member; 
     FIG. 7 is a detail similar to FIG. 6 showing the first head unseated from a recess in the second jaw member; 
     FIG. 8 is a detail similar to FIGS. 6-7 showing the shaft unseated from the initial aligned cavities for longitudinal adjustment in the second jaw member; 
     FIG. 9 is a plan view of the cutter; and, 
     FIG. 10 is a section taken along plane  10 — 10  in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings more particularly by reference character, reference number  10  refers to a cutter for plastic pipe and tubing  12  such as used for water lines. The cutter is adapted for cutting a range of different diameter plastic pipe and tubing, ranging generally from one-half inch to two inch OD. As shown in the drawings, cutter  10  has a pair of elongated jaw members  14 ,  16  pivotally connected intermediate their ends on a pivot pin  18 . As will be described in more detail below, first and second jaw members  14 ,  16  nest together in a closed position, as shown in FIG.  2 . 
     First jaw member  14  has a handle  20  at one end and a longitudinally extending knife blade  22  extending from the other end. Knife blade  22  has a cutting edge  24  and a blunt or rounded nose end  26 . At its heel  28  the blade is mounted in a slot  30  provided in handle  20 . Handle  20  is channel-shaped in cross-section with a pair of opposing sidewalls  32  connected by a bottom wall  34 . A finger loop  36 , trigger or the like is provided on bottom wall  34  serving as a means for pivoting open cutter  10 . 
     A pair of spaced internal panels  38  and end walls  40  in handle  20  at the knife mounting end define slot  30  for supporting knife blade  22  (FIG.  1 ). When inserted in handle  20 , knife blade  22  is secured in place by roll pins  42 , extending through aligned apertures in internal panels  38  and sidewalls  32 . For purposes of receiving and retaining pivot pin  18 , knife blade  22  is provided at heel  28  with an appropriate aperture in alignment with pivot pin receiving apertures  44  in each of handle sidewalls  32  and internal panels  38 . 
     When knife blade  22  and handle  20  are assembled, the blade is axially aligned with handle  20  with cutting edge  24  downwardly directed. Knife blade  22  is readily replaceable in handle  20  by removing pivot pin  18  and separating first and second jaw members  14 ,  16 . Roll pins  42  are then knocked out and the old knife blade  22  removed. A new blade is inserted, rolls pins  42  are reinserted and jaw members  14 ,  16  reassembled with pivot pin  18 . 
     Second jaw member  16  is cooperatively associated with first jaw member  14  to form cutter  10 . Second jaw member  16  is channel-shaped in cross-section with a pair of sidewalls  46  connected by a top wall  48  organized into a handle  50  at one end and a cradle  52  at the other end integrally joined together with a mounting block  54 . Cradle  52  is generally semi-circular in cross-section and extends from handle  50  to an upstanding end wall  56  of second jaw member  16 . A forward side  58  of cradle  52  is preferably vertical or hooked rearwardly to better confine pipe or tubing  12  during cutting. To permit knife blade  22  to pass completely through pipe or tubing  12 , a knife receiving slot  60  is provided in upstanding end wall  56 , cradle  52  and mounting block  54 . Reinforcing internal panels  61  (FIG. 10) may line knife receiving slot  60  in cradle  52 . In closed position as shown in FIG. 2, knife blade  22  is completely sheathed within mounting block  54 , cradle  52  and upstanding end wall  56  with first and second jaw members  14 ,  16  nested together. Knife blade  22  can pass completely through pipe or tubing  12  to be cut through knife receiving slot  60 , thereby ensuring complete severance. Knife receiving slot  60  may chamfered (not shown) along upstanding wall  56  as a blade guide. One or more stop bosses  64 , best seen in FIG. 10, may be provided on sidewalls  46  of mounting block  54  for engagement with a nub  65  on the outside of sidewalls  32  of handle  20  of first jaw member  14  to keep the jaw members nested together. 
     Pivot pin  18  is longitudinally adjustable relative to second jaw member  16  for accommodating a range of different diameter plastic pipe and tubing  12  as shown in FIGS. 3-5. For this purpose an elongated slot  62  may be provided in each of sidewalls  46  of mounting block  54 . For stepwise adjustment, a plurality of cavities  66  are formed in each elongated slot  62  along one of the longer sides. Corresponding cavities  66  of elongated slots  62  are aligned and adapted to receive pivot pin  18 . The pivot axis of knife blade  22  is changed by moving pivot pin  18  between cavities  66 . For this purpose, elongated slots  62  accommodate movement of pivot pin  18  in a direction transverse elongated slots  62  a distance sufficient for pivot pin  18  to be unseated from aligned cavities  66  in which it is initially received. 
     Pivot pin  18  has a shaft  68  with first and second heads  70 ,  72 , respectively, and may be formed of a specialized bolt with a threaded hollow tube extension into which is received a second bolt. By loosening second bolt in threaded hollow tube extension, it is possible to unseat pivot pin  18  from initial cavities  66  in which it is received and permit longitudinal movement between cavities. Once repositioned in aligned cavities, second bolt may be tightened in the threaded hollow tube extension. In the embodiment illustrated in the drawings, a resilient biasing means  74  is provided for biasing first head  70  against first sidewall  46  of mounting block  54 . A band  76  may encircle each of elongated slots  62  with lands  78  between cavities  66  on first sidewall  46  forming a recess  80  for receipt of first head  70 . Resilient biasing means  74  is illustrated as a coil spring threaded on shaft  68  between second head  72  and second sidewall  46  of mounting block  54 . It will be understood that the term “resilient biasing means” includes resilient tubing, rubber bellows and other stock members. A washer  82  may be provided between spring  74  and mounting block  54  for use as a stop for limiting transverse movement of pivot pin  18  in elongated slots  62 . 
     In use, cutter  10  as shown in FIG. 1 is assembled as in FIG.  2 . If pipe or tubing  12  has a small diameter, pivot pin  18  is set in forwardmost aligned cavities  66  in sidewalls  46 . In this position, cutting edge  24  of knife blade  22  makes about a forty-five degree angle with respect to plastic pipe or tubing  12  at initial contact. This angle of attack is believed optimal but is non-limiting. For pipe and tubing  12  with larger diameters, pivot pin  18  is unseated from initial cavities  66  and moved longitudinally in elongated slot  62  to another of the aligned cavities  66 , the particular cavities are preferably selected such that cutting edge  24  makes about a forty-five degree angle with respect to plastic pipe or tubing  12  at initial contact. The effective cutting cage of cradle  52  changes with the position of pivot pin  18 . When pivot pin  18  is in the forwardmost aligned cavities  66  as shown in FIG. 3, the effective cutting cage is reduced, better for holding smaller pipe and tubing  12 . As pivot pin  18  is moved away from cradle  52 , the effective cutting cage increases (FIGS. 4 and 5) for receipt of bigger pipe or tubing  12 . It should also be noticed that knife receiving slot  60  in mounting block  54  gives more lateral support to knife blade  22  (FIG.  5 ), preventing bending, bowing or flexing, when cutter  10  is used for bigger diameter pipe. This helps to ensure that cutter  10  makes a square cut on pipe and tubing  12  of all diameters. While cutter  10  is illustrated in the drawings with three positions for pivot pin  18 , it will be apparent that cutter may be provided with more or less cavities  66 . 
     First head  70  of pivot pin  18  is resiliently biased against sidewall  46  of mounting block  54  as shown in FIG.  6 . When a force is applied to second head  72 , first head  70  is unseated from recess  80  as shown in FIG.  7 . Then, as shown in FIG. 8, shaft  68  may be unseated from initial aligned cavities  66  permitting longitudinal movement of pivot pin  18  to another of aligned cavities, thus changing the pivot axis of first jaw member  14  in second jaw member  16 . Cutter  10  may be opened and pivot pin longitudinally adjusted relative to second jaw member  16  with one hand. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.