Patent Publication Number: US-11034039-B2

Title: Facer for end fusion of polyolefin pipes

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of U.S. Provisional patent application Ser. No. 15/709,468 titled “FACER FOR END FUSION OF POLYOLEFIN PIPES,” filed Sep. 19, 2017, now U.S. Pat. No. 10,682,780, the contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to machines used in the process of fusing polyolefin pipe and more particularly concerns facers used to prepare the opposed ends of two polyolefin pipes for butt fusion. 
     Situations in which a facer might be of use in extending a polyolefin pipe in a tight working space, such as adjacent a wall or ceiling, are not uncommon. And accessibility to such a tight working space may be further complicated by the presence of other pipes, equipment and supporting structure in the vicinity. Unfortunately, however, known facers for polyolefin pipes of mid-range diameter are poorly designed for such applications. 
     Most known mid-range diameter polyolefin pipe facers are simply too heavy to be lifted by hand into such tight working spaces. For example, facers for 24″OD polyolefin pipe typically weigh between 200 and 400 pounds. 
     Many facers are designed to face a range of pipe sizes and so their output speeds (RPM) are selected to handle the largest diameter or thickest wall pipe in their pipe range. Consequently, when they are used to face a pipe with a smaller diameter or thinner wall, they operate slower than necessary and do not make full use of their available horsepower. 
     Most known facers are designed to be mounted on carriages of only one size and their carriages are designed to be modified to permit the same facer to face a range of pipe sizes. Such facers must be sized for the largest pipe diameter in their range. Consequently, when used to face runs of smaller diameter pipe, the carriage size prevents the runs of pipe from being as close together as might otherwise be possible. 
     And most known facers produce polyolefin ribbons that can wrap tightly around the ends of the opposed pipes during facer rotation. The ribbons can block the operator&#39;s view of the pipe ends and can build up sufficiently to require periodic stoppage of the facing process to clear the ribbons. Furthermore, the ribbons can fall into, tangle in and be hard to clean out of the fusion machine. 
     It is, therefore, an object of this invention to provide a polyolefin pipe facer that is of use in extending a polyolefin pipe in a tight working space. Another object of this invention is to provide a polyolefin pipe facer that reduces the impact of a facer&#39;s weight on its utility for use in a tight working space. A further object of this invention is to provide a polyolefin pipe facer that reduces the impact of a facer&#39;s size on its utility for use in a tight working space. It is also an object of this invention to provide a polyolefin pipe facer that affords greater accessibility to tight working spaces than known facers. Yet another object of this invention is to provide a polyolefin pipe facer that makes full use of its available horsepower for more than one size of pipe. An additional object of this invention is to provide a polyolefin pipe facer that enables the running of multiple sizes of pipe closer together than is possible with known facers. And it is an object of this invention to provide a polyolefin pipe facer that controls the dispersion of polyolefin ribbons produced by the facer. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a facer is provided that can be mounted on the guide rails of a fusion machine carriage and used to prepare polyolefin pipes for end fusion. 
     The facer has a drive unit with guide rail brackets and an output shaft. The brackets are adapted for tool-free engagement preventing horizontal and vertical displacement of the drive unit relative to the guide rails. Two blade holders are adapted for tool-free engagement on and rotation with the output shaft of the drive unit with the blade holders in parallel and on opposite sides of the drive unit. A motor assembly is adapted for tool-free engagement preventing horizontal and vertical displacement of the motor assembly in relation to the drive unit. A linkage engages the output shafts of the drive unit: and the motor assembly for transmission of power from the motor assembly output shaft to a drive unit output shaft. The linkage may be a mechanical coupling and may include a gearbox. 
     The facer drive unit has a horizontal output shaft parallel to the guide rails. The free ends of the horizontal output shaft are on opposite sides of the drive unit and have penultimate portions of identical non-circular cross-section and ultimate portions with identical concentric circular adapters. Each blade holder has a center opening complementing the penultimate portion of a respective free end of the horizontal output shaft. Two latching assemblies, each surrounding its respective blade holder center opening, are operable to secure their respective blade holder to a respective one of the shaft concentric circular adapters with the center opening engaged on its respective shaft penultimate portion and with the two blade holders in parallel relationship. Preferably, each non-circular free end of the horizontal output shaft is hexagonal and each latching assembly is a split wedge clamp ring. The facer may have multiple pairs of blade holders of different diameters interchangeable with two blade holders. At least one blade is mounted on each blade holder at an angle selectable to cause ribbons of polyolefin shaved thereby to be dispensed either inside of or outside of their respective pipe. 
     The drive unit module of die facer has an elongated frame and two guide rail brackets, one on each end portion of the frame. Two arrays of co-operable registries, each array corresponding to a respective one of the guide rail brackets, are configured to locate the guide rail brackets in any of multiple symmetrically spaced relationships from a center of the frame. Two indexing assemblies, one on each end portion of the frame, configured to secure the guide rail brackets in any of multiple symmetrically spaced relationships, are used to space the guide rail brackets in the spaced relationship closest to the distance between the guide rails. The guide rail brackets are U-shaped. A horizontal U-shaped bracket is engageable on one of the guide rails by lateral motion of the frame. A vertical U-shaped bracket is engageable on the other guide rail by downward motion of the vertical U-shaped bracket with the horizontal U-shaped bracket engaged on the one of the guide rails. A clamp mounted on the horizontal U-shaped bracket constrains facer motion in a vertical plane. A clamp mounted on the vertical U-shaped bracket constrains facer motion in a horizontal plane. A latch assembly mounted on the vertical U-shaped bracket retains the facer on the guide rails. Each array of co-operable registries has multiple apertures spaced longitudinally on the elongated frame and an aperture on its respective one of the guide rail brackets. Each index assembly is a spring pin. The linkage has an input shaft, an output shaft and a gearbox between the input and output shafts. Two adapters, one on each end of the linkage output shaft, enable tool-free engagement on and rotation with the linkage output shaft of a respective blade holder with the blade holders in parallel. A mounting socket is adapted for engagement with the frame of the drive motor assembly. 
     Each blade holder module has a disk with a center opening for closely fitting a perimeter of a penultimate portion of the end of the drive unit module output shaft. A latching assembly surrounds the center opening and is operable to secure the disk to an ultimate portion of the end of the drive unit module output shaft with a disk perpendicular to the shaft. A blade is mounted on a distal face of the disk relative to the output shaft of the drive unit at either an angle causing ribbons of polyolefin shaved thereby to be dispensed inside of the pipe or an angle causing ribbons of polyolefin shaved thereby to be dispensed outside of the pipe. The disk has a recess in its distal face with two pairs of two holes in the recess registrable with two holes in the blade. Alignment of the two holes in the blade with one of the two pairs of holes in the disk causes the blade to be at the angle causing ribbons of polyolefin shaved thereby to be dispensed inside of the pipe. Alignment of the two holes in the blade with the of the two pairs of holes in the disk causes the blade to be at the angle causing ribbons of polyolefin shaved thereby to be dispensed outside of the pipe. The center opening is non-circular and preferably hexagonal. The latching assembly is preferably a split wedge clamp ring. 
     The motor assembly module has a motor, a gearbox driven by the motor, an output shaft from the gearbox and a coupler on a free end of the output shaft. A connector has plug-and-socket components, one fixed to the motor assembly module and the other fixed to the frame of the drive unit module. The components have a configuration adapted for tool-free engagement preventing horizontal and vertical displacement of the motor assembly module in relation to drive unit module with the gearbox output shaft coupler engaged with the input shaft coupler for rotation with the gearbox output shaft. In this configuration, the couplers are spaced from their respective components so as to align the couplers on a common center axis of the drive unit input shaft and the gearbox output shaft. One component of the connector is adapted to telescope in the other component to engage the couplers. Apertures in the telescoping components are alignable to cooperate with a detent pin to secure them with the couplers engaged. The telescoping components are preferably vertically aligned tubular members of square cross-section. The gearbox is preferably a multi-speed gearbox operable at a speed selected to correspond to a cross-section of a pipe being faced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which: 
         FIG. 1  is a perspective view of a preferred embodiment of a facer in accordance with the invention for use in a process for end fusion of polyolefin pipe; 
         FIG. 2A  is an enlarged perspective view of a preferred embodiment of the drive unit of the facer of  FIG. 1 ; 
         FIG. 2B  is a top plan view illustrating a preferred embodiment of the gear assembly housed in the gearbox of the drive unit of  FIG. 2A : 
         FIG. 2C  is a bottom plan view of the gear assembly of  FIG. 2B ; 
         FIG. 2D  is an elevation view of the gear assembly of  FIG. 2B  as seen in the direction D-D of  FIG. 2A ; 
         FIG. 2E  is an elevation view of the gear assembly of  FIG. 2B  as seen in the direction E-E of  FIG. 2A ; 
         FIG. 2F  is an elevation view of the gear assembly of  FIG. 2B  as seen in the direction F-F of  FIG. 2A ; 
         FIG. 3A  is an enlarged perspective view illustrating one cutting face of a preferred embodiment of the two blade holders of the facer of  FIG. 1  with its blades in a “ribbon-inside” configuration; 
         FIG. 3B  is an enlarged perspective view illustrating the other cutting face of the preferred embodiment of the two blade holders of the facer of  FIG. 1  with its blades in a “ribbon-outside” configuration; 
         FIG. 3C  is an enlarged perspective view illustrating one cutting face of a preferred embodiment of the two blade holders of the facer of  FIG. 1  with its blades in a “ribbon-inside” configuration; 
         FIG. 3D  is an enlarged perspective view illustrating the other cutting face of the preferred embodiment of the two blade holders of the facer of  FIG. 1  with its blades in a “ribbon-outside” configuration; 
         FIGS. 3E, 3F and 3G  are perspective views illustrating large, medium and small blade holders, respectively, for use with the same drive unit according to  FIG. 2A ; 
         FIG. 4  is a perspective view of a preferred embodiment of the motor assembly of the facer of  FIG. 1 ; 
         FIG. 5  is a perspective view of the three modules of the facer of  FIG. 1  arranged for assembly into a facer according to  FIG. 1 ; 
         FIG. 6  is a perspective view of the drive unit seen in  FIG. 5  after mounting on the guide rails of a fusion machine carriage; 
         FIG. 7  is a perspective view of the blade holders seen in  FIG. 5  after mounting on the drive unit which is on the guide rails as seen in  FIG. 6 ; 
         FIG. 8  is a perspective view of the motor assembly seen in  FIG. 5  after mounting on the drive unit with the blade holders as seen in  FIG. 7 ; and 
         FIGS. 9A and 9B  are side elevation views illustrating the assembled facer of  FIG. 8  using the large and small blade holders of  FIGS. 3E and 3G , respectively. 
     
    
    
     While the invention will be described in connection with preferred embodiments thereof, it will be understood that it is not intended to limit the invention to those embodiments or to the details of the construction or arrangement of parts illustrated in the accompanying drawings. 
     DETAILED DESCRIPTION 
     The Facer 
     Looking first at  FIG. 1 , a modular facer F is adapted to be engaged on the guide rails R (seen in  FIGS. 6-8 ) of a fusion machine carriage (not shown) for the purpose of facing the ends of polyolefin pipes P (seen in  FIGS. 9A-9B ) for butt fusion. The term “polyolefin” identifies a most common application of the modular facer but is intended to include “nylon,” PVC and other fusible non-polyolefin pipes. 
     The facer F is modular in the sense that it employs three types of modules including a drive unit  10 , two blade holders  60  and a motor assembly  80  that are separable from one another. Each module  10 ,  60 ,  80  is independently light enough to be hand-lifted along walls and up to ceilings (not shown). However, the modules  10 ,  60  and  80  can each be exchanged or modified without use of tools in order to change the geometry of the facer F so that the same facer F can be used to face different diameters of pipe within working spaces dictated by the diameter of the pipe and not by the fixed geometry of a fusion machine and facer. 
     This is made possible by use of a drive unit  10 , seen in  FIGS. 1 and 2A-2F , that is adjustable to accommodate different spacing between guide rails R of different fusion machines, by use of blade holders  60 , seen in  FIGS. 1 and 3A-3G , that are interchangeable to accommodate different diameters of pipe P and by use of a motor assembly  80 , seen in  FIGS. 1 and 4 , that has multispeed capability to accommodate the total area of material to be faced, a total which varies in relation to the diameter and thickness of the pipe. 
     The Drive Unit 
     Turning to  FIG. 2A , a preferred embodiment of the drive unit  10  of the facer F is seen mounted on the guide rails R of a carriage of a machine used to fuse polyolefin pipe end-to-end. An elongated frame  11  has two guide rail brackets  12  and  13 , one on each end portion of the frame  11 . Two sets of registries  14  and  15 , each corresponding to a respective guide rail bracket  12  or  13 , are configured to locate their respective brackets  12  or  13  in any of multiple symmetrically spaced relationships from a center axis  21  of the elongated frame  11 . Looking at  FIG. 2A  in the direction D-D, the left hand registries  14  and  15  are not seen but are a mirror image of the right hand registries  14  and  15 . Two indexing assemblies  16 , one on each end portion of the elongated frame  11 , secure their respective brackets  12  or  13  in any selected one of multiple symmetrically spaced relationships at the spaced relationship that is closest to the distance between the guide rails R. Thus, a single drive unit frame  11  can, for example, fit six different sizes of fusion machine carriages if the locations of the guide rail brackets  12  and  13  have registries  14  that are adjustable to six different carriage guide rail spacings. 
     The elongated frame  11  as illustrated is fixed in overall length. The guide rail brackets  12  and  13  slide inward for smaller fusion machine carriages but the frame overall length of the frame  11  stays the same. However, the frame  11  may be retractable within the space between the guide rail brackets  12  and  13 , for example by use of a telescoping frame or exchangeable frame arms. 
     As seen in  FIG. 2A , both guide rail brackets  12  and  13  are U-shaped with one being horizontal  12  and the other vertical  13 . The horizontal bracket  12  is engageable on its respective guide rail R by lateral motion of the elongated frame  11  and the vertical bracket  13  is engageable on its respective guide rail R by downward motion of its respective end of the elongated frame  11  with the horizontal bracket  12  engaged on its respective guide rail R. 
     Also as shown in  FIG. 2A , each set of registries  14  and  15  includes multiple apertures  14  spaced longitudinally on the elongated frame  11  and an aperture  15  on its respective guide rail bracket  12  or  13 . Each index assembly  16  is a spring pin that, when its respective bracket aperture  15  is aligned with a selected one of its respective multiple apertures  14  on the elongated frame  11 , can be engaged in its respective aligned apertures  14  and  15  to secure the brackets  12  and  13  at symmetrical spacing from the center axis  21  of the elongated frame  11 . 
     After the horizontal guide rail bracket  12  is registered and indexed on the frame  11 , a clamp  17  mounted on the bracket  12  is tightened by use of a knob  18  to constrain facer motion in a vertical plane. After the vertical guide rail bracket  13  is registered and indexed on the frame  11 , a clamp (not seen) mounted on the bracket  13  is tightened by use of a knob to constrain facer motion in a horizontal plane. The vertical bracket clamp is similar to the horizontal bracket clamp  17  but in a 90° rotated orientation. 
     A latch assembly  19  mounted on the vertical guide rail bracket  13  retains the facer F on the guide rails R. As best seen in  FIGS. 9A and 9B , the latch assembly  19  has a latch arm that pivots to cross under the guide rail R and engage a latch slot on the other side. A pull spring pin secures the arm in the latched or unlatched position. The horizontal guide rail bracket  12  cannot slide off its guide rail R as long as the vertical guide rail bracket  13  is on its guide rail R. 
     In the embodiment of  FIG. 2A , a mounting socket  22  on the elongated frame  11 , as shown fixed on the top of the frame  11  in alignment with the center axis  21 , is adapted for engagement with the frame  85  of the motor assembly  80 , hereinafter discussed. And each of the guide rail brackets  12  and  13  is equipped with a handle  23  to facilitate lifting and manipulating the drive unit  10  into position on the guide rails R. 
     Also, as shown in  FIG. 2A , the drive unit  10  has a linkage  24  with an input shaft  25  and an output shaft  26 . Two adapters  27  and  28 , one on each end of the linkage output shaft  26 , enable tool-free engagement and rotation of respective blade holders  60  on and with the linkage output shaft  26  with the blade holders  60  in parallel. Preferably, the linkage  24  includes a hypoid gear  29  that converts input shaft  25  rotation about a vertical axis to output shaft  26  rotation about a horizontal axis. This enables the motor assembly  80  to be centered and balanced, rather than cantilevered and imbalanced, on the input drive  10 . 
     Looking at  FIGS. 1 and 2A , a preferred embodiment of the drive unit linkage  24  extends from its input coupler  31  through a gearbox  32  to the adapters  27  on its output shaft  26 . As seen in  FIGS. 2B-2F , the linkage  24  is illustrated with the housing of the gearbox  32  removed. The linkage input shaft  25  rotates on ball bearings  33  in unison with the input coupler  31  on one of its ends and a drive sprocket  34  on its other end. The input coupler  31  is adapted to mate with an output shaft coupler  84  of the motor assembly  80  to transfer torque via the input shaft  25  to the drive sprocket  34 . The drive sprocket  34  is engaged by a roller chain  35  to a driven sprocket  36  with its sprocket shaft  37  mounted on tapered roller bearings  38 . In this embodiment, the “sprocket shaft”  37  is an extension of the pinion  39  and extends in parallel with the drive unit input shaft  25  to a pinion  39  engaged with a ring gear  41 . The ring gear  41  and pinion  39  redirect the rotational motion of the input and drive sprocket shafts  25  and  37  about their vertical axes to the rotational motion of the output shaft  26  of the drive unit  10  about its horizontal axis. 
     Continuing to look at  FIGS. 2B-2F , the output shaft  26  of the drive unit  10  extends at each end to respective adapters  27  and  28  configured for tool free connection to a respective blade holder  60 . As shown, the blade holder adapters  27  have identical penultimate noncircular portions  42  and identical ultimate concentrically circular portions  43  cooperable for mating with components of its respective blade holder  60  hereinafter described. As shown, die penultimate noncircular portion  42  of the adapters  27  are hex shaped. 
     The Blade Holder 
     Looking now at  FIGS. 1 and 5 , two blade holders  60  are mounted on the drive unit  10  with the blade holders  60  parallel to each other and on opposite sides of drive unit  10 . As shown, each blade holder  60  is a disk  61  with a center opening  62  for closely fitting a perimeter of an end of the facer output shaft  26 . Each blade holder  60  has a latching assembly  63  operable to secure the disk  61  to an end of the facer output shaft  26 . 
     Turning to  FIGS. 3A-3B , each blade holder  60  is preferably a circular disk  61  with a center opening  62  complementing its respective penultimate noncircular portion  42  of the horizontal output shaft  26  of the drive unit  10 . Each blade holder latching assembly  63  surrounds its center opening  62 . The latching assembly  63  is operated to secure its blade holder  60  to the drive unit output shaft  26  after the center opening  62  of the blade holder  60  has been fully engaged on the penultimate noncircular portion  42  of the drive unit output shaft  26 . Preferably, and as seen in  FIGS. 3A-3B , the latching assembly  63  is a split wedge clamp ring adapted to grip the ultimate concentrically circular portion  43  of the drive unit output shaft  26  that will extend through the latching assembly  63  when the blade holder  60  is fully engaged on the penultimate noncircular portion  42  of the drive unit output shaft  26 . As shown, the noncircular portions  42  of the drive unit output shaft  26  and the center openings  62  of the blade holder disk  61  are hexagonal. 
     Now looking at  FIGS. 3C-3D , each blade holder  60  has at least one blade  64  mounted on an outside face of the disk  61 . If, as seen in  FIG. 3C , the shaving edge  65  of the blade  64  is at an angle  66  in which its distal end leads its travel, shaved ribbons S of polyolefin will be dispensed inside of the pipe P being shaved. If, as seen in  FIG. 3D , the shaving edge  65  of the blade  64  is at an angle  67  in which its distal end trails its travel, shaved ribbons S of polyolefin will be dispensed outside of the pipe P being shaved. 
     As best seen in  FIGS. 3C-3D , a blade  64  is mounted in a V shaped recess  68  in the outer face of the disk  61 . The recess  68  has two sets  69  and  71  of at least two holes, as shown two sets of three holes, which are registrable with at least two holes in the blade  64 . The alignment of the blade holes with one set  69  of recess holes orients the blade  64  at the angle  66 , causing shaved ribbons S of polyolefin to be dispensed inside of the pipe P. The alignment of the blade holes with the other set  71  of recess holes orients the blade  64  at the angle  67 , causing shaved ribbons S of polyolefin to be dispensed outside of the pipe P. As shown, the blade  64  is secured in the recess  68  using screws  72 . Multiple blades  64  can be mounted on a disk  61 , preferably at equal angular displacements on die disk  61 , with each blade  64  in a separate recess  68 . 
     The two blade holders  60  are mirror images to provide proper orientation of the blades and position in their V shaped recesses  68 . Each blade holder  60  is mounted on its respective side of the facer F so that when rotating the blade edge  65  is leading and cutting and not trailing and dragging with the blade  64  on the trailing side of the V-shaped recess  68 . 
     For normal operation, the blade  64  is oriented to disperse the shaved ribbons S inside the pipe P, as seen in  FIG. 3C . They remain inside the pipe P during the entire facing operation. As a result, the ribbons S do not tangle in the facer F or the fusion machine and do not wrap tightly around the pipe P. Therefore, it is not necessary to periodically stop facing to clear the shaved ribbons S. Furthermore, ribbons S do not wrap around the pipe P, so the operator&#39;s view of the pipe periphery is not blocked. After facing, cleanup is easily accomplished by pulling a bundle of ribbons S from each pipe end. 
     For fusion of vertically oriented pipe P, the blade  64  is positioned as seen in  FIG. 3D  so ribbons S drop outside of the pipe P and down and do not tangle in the facer F. Also, for fusion of vertically oriented pipe P, the blade  64  on the lower blade holder  60  can be angled to disperse shaved ribbons S outside of its respective pipe P and the blade  64  on the upper blade holder can be angled to disperse shaved ribbons S inside of its respective pipe P. 
     Moving on to  FIGS. 3E-3G , for the same drive unit  10 , pairs of blade holders  60  of one diameter are interchangeable on the output shaft adapters  27  and  28  with pairs of blade holders  60  of another diameter. For example, blade holders  60  of large, intermediate and small outer diameter  73 ,  74  and  75 , shown in  FIGS. 3E, 3F and 3G , respectively, but all have the same size center openings  62  and latching assemblies  63 . Furthermore, the lengths of the blades  64  can be sufficient to accommodate different diameter pipes P. Pipes P are typically of standardized sequential diameters. If, for example, the blades  64  are each sufficiently long to accommodate two sequential diameters of pipe P and the large, intermediate and small outer diameter  73 ,  74  and  75  blade holders  60  shown in  FIGS. 3E, 3F and 3G , respectively, are available for use, the same drive unit  10  can be used to face six different diameters of pipe P. 
     As seen in  FIGS. 3A-3G , the weight of a blade holder  60  can be reduced by voids  76  through the disk  61 . However, if the shaved ribbons S are to be dispensed inside of the pipe P as by the blade holder  60  of  FIG. 3C , it may necessary to close the voids  76  in some applications. 
     The Motor Assembly 
     Turning to  FIG. 4 , the motor assembly  80  has a motor  81  with a gearbox  82  driving an output shaft  83  with a coupler  84  on its free end. In the embodiment of  FIG. 4 , a mounting frame  85  attached to the motor assembly  80  by a bracket  86  has a mounting plug  87  adapted for engagement with the socket  22  on the elongated frame  11  of the drive unit  10 , as shown in  FIG. 2A . The coupler  84  on the motor assembly output shaft  83  and the input shaft coupler  31  of the drive unit  10  are spaced from the plug  87  and the socket  22  to align the couplers  84  and  31  on a common center axis  88 . Thus, the couplers  84  and  31  are automatically mechanically engaged for rotation in unison when the motor assembly  80  is mounted on the drive unit  10  by telescoping the plug  87  into the socket  22 . A detent pin  89  inserted into aligned apertures  91  secures the telescoped plug  87  and socket  22  with the couplers  84  and  31  engaged. 
     The plug and socket components  87  and  22  could be switched to the drive unit  10  and motor assembly  80 , respectively. In either configuration, the socket  22  and plug  87  are adapted for tool-free engagement preventing horizontal and vertical displacement of the motor assembly  80  in relation to the drive unit  10 . Preferably, the telescoping socket  22  and plug  87  are vertically aligned tubular members of square cross-section. 
     The gearbox  82  is preferably a multi-speed gearbox operable at a speed selected to correspond to a cross-section of a pipe P being faced. A two-speed gearbox  82  can be set to low speed for larger and/or thicker pipe P and set to high speed for smaller and/or thinner pipe P. The horsepower required is governed in part by the speed of the blade  64 , which is a function of RPM and pipe diameter, and wall thickness of the pipe P. The maximum required horsepower and blade holder RPM are governed by the largest and thickest pipe P. If the same RPM is used for smaller and thinner pipe, the blade speed will be slower and will not draw the full available horsepower. Using the high-speed setting for smaller/thinner pipe P reduces facing time. Alternatively, the drive unit gearbox  32  may be adapted to provide the two-speed operation of the drive unit output shaft  26  using a single speed motor assembly  83 . 
     A pair of handles  92 , each spaced from the motor  81  and gearbox  82  on a corresponding wing  93  of the motor assembly  80 , extend on axes  94  perpendicular to a diameter  95  of the motor  81  and gearbox  82  to facilitate lifting and manipulating the motor assembly  80  into position on the drive unit  10 . 
     Assembly of the Facer 
     Looking at  FIGS. 5 and 6 , in assembling the facer F for use, the drive unit  10  is first mounted on the carriage guide rails R. This is accomplished by lifting the drive unit  10  above and squared with the carriage guide rails R, tilting the drive unit  10  so that the horizontal guide rail bracket  12  points toward one guide rail R, sliding it onto that guide rail R until that guide rail R is fully seated in the horizontal guide rail bracket  12 , rocking the drive unit  10  on that guide rail R toward the other guide rail R until the vertical guide rail bracket  13  is fully seated on the other guide rail R and then swinging the vertical guide rail bracket latch  19  to its closed condition. 
     Looking at  FIGS. 5 and 7 , with the blades  64  secured to their respective blade holders  60  at the desired angle for inside or outside dispersion of shaved ribbons S, the two blade holders  60  can each be lifted up and attached one at a time to the drive unit  10  by sliding them fully onto the hex nuts on the drive unit output shaft  26  and closing the latching assemblies  63  on the blade holders  60 . 
     Looking at  FIGS. 5 and 8 , the motor assembly  80  is mounted on the drive unit  10  by raising the motor assembly  80  above the drive unit  10 , aligning the plug  87  of the motor assembly  80  with the socket  22  of the drive unit  10  and lowering the motor assembly  80  to fully engage the plug  87  in the socket  22 , thereby simultaneously engaging the coupler  84  of the motor assembly output shaft  83  with the coupler  31  of the drive unit input shaft  25  and aligning the apertures  91  in the plug  87  and the socket  22 . The detent pin  89  can then be inserted into the aligned apertures  91 , completing the assembly of the facer F. Disassembly of the facer F involves essentially a reversal of the steps of assembly. 
     The same facer F is seen in its assembled condition in  FIG. 9A  with large diameter blade holders  60 , as seen in  FIG. 3E , and in  FIG. 9B  with small diameter blade holders  60 , as seen in  FIG. 3G . The same drive unit  10  is used at its widest spacing of brackets in  FIG. 9A  and at its narrowest spacing of brackets in  FIG. 9B . The same motor assembly  80  is used, but would be set at its lowest speed in  FIG. 9A  and at its highest speed in  FIG. 9B . The facer F is seen in a horizontal orientation in  FIGS. 9A and 9B  and the blades  64  are angled for dispersing shaved ribbons S into the pipe P as seen in  FIG. 3C . If the facer F were rotated 90° to a vertical orientation, the upper blade  64  would be angled for dispersing shaved ribbons S inside of the pipe P as seen in  FIG. 3C  and the lower blade  64  would be angled for dispersing shaved ribbons S outside of the pipe P as seen in  FIG. 3D . 
     Thus, it is apparent that there has been provided, in accordance with the invention, a facer that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art and in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit of the appended claims.