Patent Abstract:
A tube scraping tool comprises: a handle; and a blade, carried by the handle. The tool has first and second laterally spaced apart portions for engaging the tube outer diameter (OD) surface during a drawing of the tool along the tube. The blade has a cutting edge trailing the first and second portions during the drawing and laterally between the first and second portions.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to plastic piping. More particularly, the invention relates to preparation of plastic pipe/tube material for electro-fusion bonding. 
         [0002]    In order to connect thermoplastic piping systems together via electro-fusion methods it is standard practice to remove the outer oxidized surface of the pipe to expose clean un-contaminated plastic. Typical previous methods rely on fixed or pivoting cutting tools and/or internal drive mandrels to remove the outer oxidized layers. 
         [0003]    Examples of prior tools include those shown in U.S. Pat. Nos. 5,600,862, 6,434,776, and 6,698,321 and US patent application publications 2011232434A1 and 20150321260A1. A particular tool used with larger diameter pipe is the ROTARY PEELER RS by Georg Fischer Central Plastics of Shawnee, Okla., USA. 
         [0004]    US patent application publication 20150321260A1 discusses problems of peeling out-of-round pipe. Smaller diameter pipe will acquire an oval shape due to coiling. 
         [0005]    Larger diameter pipe (e.g., shipped and stored in straight lengths) may acquire similar eccentricity due to stacking and handling 
         [0006]    To ensure sufficient depth of peeling, it is known to pre-cut a witness score or groove in the outer diameter of the pipe. If the subsequent peel is of a depth smaller than that of the groove, the removed curl from the peeling will be discontinuous, terminating and then restarting each time the peeler blade reaches the groove. Thus, observing a continuous peel confirms that the peel is at least the depth of the witness groove. 
       SUMMARY OF THE INVENTION 
       [0007]    One aspect of the disclosure involves a tube scraping tool comprising: a handle; and a blade, carried by the handle. The tool has first and second laterally spaced apart portions for engaging the tube outer diameter (OD) surface during a drawing of the tool along the tube. The blade has a cutting edge positioned to trail the first and second portions during the drawing and laterally between the first and second portions. 
         [0008]    A further embodiment may additionally and/or alternatively include the blade has a passageway for passing a curl of removed material. 
         [0009]    A further embodiment may additionally and/or alternatively include the cutting edge protruding beyond a remaining portion of the blade at an inlet to the passageway by a height of at least 0.10 mm. 
         [0010]    A further embodiment may additionally and/or alternatively include the height being 0.10 mm to 0.20 mm. 
         [0011]    A further embodiment may additionally and/or alternatively include the blade being steel. 
         [0012]    A further embodiment may additionally and/or alternatively include the blade being mounted to the handle via an axle. 
         [0013]    A further embodiment may additionally and/or alternatively include the axle providing the blade with a restricted non-zero rotational range. 
         [0014]    A further embodiment may additionally and/or alternatively include the restricted non-zero rotational range being at least 0.5°. 
         [0015]    A further embodiment may additionally and/or alternatively include the handle having a compartment partially receiving the blade. 
         [0016]    Another aspect of the disclosure involves a method for scraping a witness groove into the outer diameter (OD) surface of a tube. The method comprises: drawing a tool longitudinally along the OD surface. During the drawing, the tool is supported by laterally spaced apart portions engaging the OD surface and a blade trailing the laterally spaced apart portions. 
         [0017]    A further embodiment may additionally and/or alternatively include, during the drawing, a curl of material passing through a passageway of the tool. 
         [0018]    A further embodiment may additionally and/or alternatively include rotary peeling of the tube to a depth below a depth of the groove. 
         [0019]    A further embodiment may additionally and/or alternatively include electro-fusing a fitting around the tube after the rotary peeling. 
         [0020]    A further embodiment may additionally and/or alternatively include the drawing being a drawing by hand. 
         [0021]    A further embodiment may additionally and/or alternatively include the method being performed on a plurality of tubes of a given nominal size. The trailing location of the blade and a pivoting of the blade accommodate tube-to-tube variations in curvature at a grooving location. 
         [0022]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a view of a grooving tool cutting a groove in a pipe. 
           [0024]      FIG. 2  is a side view of the tool and pipe. 
           [0025]      FIG. 3  is a first end view of the tool and pipe. 
           [0026]      FIG. 4  is a second end view of the tool and pipe. 
           [0027]      FIG. 4A  is an enlarged view of a blade-to-pipe engagement taken at detail  4 A of  FIG. 4 . 
           [0028]      FIG. 5  is a central longitudinal sectional view of the tool and pipe taken along line  5 - 5  of  FIG. 4 . 
           [0029]      FIG. 5A  is an enlarged view of the blade-to-pipe engagement taken at detail  5 A of  FIG. 5 . 
           [0030]      FIG. 6  is an exploded view of the tool. 
           [0031]      FIG. 7  is a central longitudinal sectional view of the blade taken along line  7 - 7  of  FIG. 6 . 
       
    
    
       [0032]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0033]      FIG. 1  shows a tool  20  being used to apply a score (groove)  22  in the outer diameter (OD) surface  24  of a tube  26 . The tube extends from a first end  28  to a second end  30  ( FIG. 2 ) and has an inner diameter (ID) or inner/interior surface  32  surrounding a tube interior space  34 . The tube has an inner diameter of D I  and an outer diameter of D O  leaving a wall thickness T W  therebetween. The tube is shown having a central longitudinal axis  500 . As a practical matter, manufacturing and in-use considerations (e.g., deforming of the tube during shipping) may leave the tube slightly out-of-round or otherwise imperfect.  FIG. 4A  shows the groove  22  being cut with a depth D G . The groove is cut by drawing the tool  20  in a direction  502  ( FIG. 5 ) parallel the axis  500 . Exemplary D G  is 0.005 inch to 0.006 inch (0.13 mm to 0.15 mm) for a 0.007 inch to 0.010 peel (0.18 mm to 0.25 mm). More broadly, an exemplary groove depth is 0.10 mm to 0.20 mm. 
         [0034]    The tool  20  comprises a combination of a handle/body  40  and a blade  42 . The blade  42  is held partially within a compartment  44  of the body such as via an axle  46 , discussed below. Exemplary body materials are aluminum alloys or plastics. The body may be made of machining of alloy or molding of plastic or via additive manufacturing processes. The exemplary illustrated body is monolithic. However, alternative hollow assemblies are possible. 
         [0035]    The exemplary blade  42  ( FIG. 6 ) is formed as a modified rectangular prism extending from a first end (face)  50  to a second end (face)  52  and having a first lateral side  54  ( FIG. 4 ) and a second lateral side  56 . The blade has an inboard (facing toward the axis  500  when in use) face  58  and an outboard face  60  ( FIG. 7 ). In the exemplary blade, the lateral faces are the largest faces and the end faces are the smallest faces. A transition  62  between the first end face  50  and the inboard face  58  is rounded to avoid catching as the blade is drawn along the tube. The inboard face  58  comprises a generally flat main portion  68  and a cutting ramp  70 . The ramp  70  has an inboard face  72  that extends from a leading end  74  to a trailing end  76 . The ramp has lateral surfaces  78  and  80  ( FIG. 6 ). At the leading end  74 , a leading edge of the surface  72  falls along a cutting edge  84 . A protrusion of the edge  84  beyond the surface  68  generally corresponds to the groove depth D G . The blade is held in place by the axle  46  passing through a transverse hole  88  in the blade having an axis  510 . In at least some embodiments, the compartment  44  is sized to allow the blade a small range of rotation (e.g., at least 0.5° or at least 1.0° or an exemplary 1.0° to 2.0° (e.g., nominal 1.5° )) about the axis  510  via the axle  46 . This small degree of freedom may allow the blade to maintain an ideal orientation despite variations in tube OD. The upper ends on the range are merely a matter of convenience to keep the blade in an orientation close enough so that the applying to the pipe can bring the blade into a more exact alignment. Thus, although only 1° or so may be desired/needed, even 10° or more may not be detrimental. These variations may not merely be tolerances but rather variations associated with use on different nominal sizes of tube. Exemplary tube outer diameter is 1.5 inch or greater (38 mm or greater). Exemplary tube (and electrofusion fitting) materials are polyethylene (PE, e.g., HDPE or LDPE), polypropylene (PP), polyvinyl chloride (PVC), and the like. 
         [0036]    To evacuate material cut from the groove, the exemplary blade comprises a channel or passageway  90  extending from an opening  92  in the inboard face  58  to an opening  94  in the second end face  52 . As the blade is drawn along the pipe, the edge  84  cuts a curl  99  ( FIG. 5 ) of material which then can pass through the opening  92  and out the opening  94 . 
         [0037]    The exemplary blade material is steel. The blade may be machined from strip or bar stock. For example, the stock may have a thickness corresponding to the dimension between the faces  54  and  56  and another dimension corresponding to an overall height between the face  60  and at least the edge  84 . The remaining surface  58  may be machined to create the portion  64  leaving the ramp  70  proud. The holes  88  and  90  may then be drilled such as to form circular sectioned holes. The edge  84  may be left proud by a height equal to the desired groove depth. The corners of the cross-section viewed in  FIG. 7  may then be machined such as by grinding so as to form the rounded transition  62  and bevels on the other corners. 
         [0038]    The body  40  ( FIG. 2 ) extends from a first longitudinal end  120  to a second longitudinal end  122  and has respective first and second lateral sides  124  and  126 . The body has an underside  128  ( FIG. 6 ) and an opposite top or outboard extremity  130 . The underside  128  is formed of a generally channel-like section having a pair of side rails  140 ,  142  and having a base surface  144 . Each of the rails  140 ,  142  has a leading portion  150 ,  151  and a trailing portion  152 ,  153 . The leading portion is higher than the trailing portion. In operation, the leading portions  150  of the two rails would contact circumferentially spaced locations along the tube surface  24  while the blade contacts a third location. This provides a precise cutting depth regardless of roundness of the tube. For example, if the two rails at full height were adjacent the blade, then the groove would have greater depth in a smaller diameter pipe than in a larger diameter pipe. Similarly, in an eccentric (e.g., slightly flattened) pipe, the groove would be deeper at a circumferential location having a smaller radius of curvature than another location. Thus, the recessing of the trailing portions  150  and the associated three-point contact renders groove depth less sensitive to eccentricity. 
         [0039]      FIG. 6  also shows axle holes  160  on either side of the compartment  44  for receiving end portions of the axle  46  (e.g., in a press fit situation). Exemplary press fits may involve the axle being press fit into one or both of the portions of the body beside the compartment and/or into the hole  88 . Alternative mounting of the blade may include screwing or other fasteners. As is noted above, the witness groove is formed by manually longitudinally drawing the tool from the end of the tube by the distance intended for subsequent peeling and electro-fusion (e.g., the longitudinal span of the electro-fusion socket into which the tube is to be inserted). The rotary peeling may be performed in one or more stages with a continuous curl spanning the groove evidencing sufficient depth of peeling. Thereafter, the tube end (now ungrooved at least over the relevant electro-fusion portion) may be inserted into the electro-fusion fitting and electro-fused. 
         [0040]    One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

Technology Classification (CPC): 1