Abstract:
A portable apparatus for cutting roofing shingles at various angles comprises a rigid frame assembly, a first cutting blade affixed to the frame assembly, a cutting blade assembly comprising a blade-supporting arm pivotally attached to the frame and a second cutting blade affixed to that arm and extending parallel to the first cutting blade, the cutting blade assembly being pivotable so as the second cutting blade can be pivoted into and out of a shingle-shearing relationship with the first cutting blade, and the blade-supporting arm being adjustable laterally of the first cutting blade so as to assure a clean shearing action. A movable guide fence assembly mounted on the frame accurately determines the angle at which a shingle is to be cut.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     1. Field of Invention 
     This invention is an improved and more versatile apparatus for cutting roofing shingles. 
     2. Description of Prior Art 
     Installation of roofing shingles requires many cuts to be made in various directions. Traditional practice calls for use of a hand-held utility-type knife which is slow and inaccurate and potentially dangerous since some types of shingles need multiple passes and considerable force with the knife, which can and does slip, causing injury. Several designs have been proposed for an apparatus to cut shingles, however, these designs are limited in performance in various ways. The underlying problem is that shingles resist being cut, and particularly, cut neatly. This is due to their thickness and toughness and the wide range of workability resulting from the extremes of ambient temperature during which they are installed. In cold weather, shingles are stiff and brittle, resistant to cutting, and tend to crack without careful handling. In hot weather, they become exceedingly soft and pliable and prone to tearing. Also, in hot weather, the asphaltic component of the shingles softens into a semi-melted state and accumulates as a tarry deposit on tools. Under any weather conditions, debris and granules from the surface of the shingles are dislodged in handling and collect within the workings of an apparatus not designed to tolerate them. 
     A shingle cutting apparatus must also take into account that regardless of the design employed a vigorous thrust of the mechanism will be required to effect its operation, again due to the resistance of the shingle being cut. This requirement can be satisfied by proper provision for the use of leverage, however, the apparatus must be configured to remain stable in the face of the forceful stroke by the user. If the apparatus moves or tips in use, it will be inconvenient or dangerous to use. 
     Prior art fails to overcome these difficulties and therefore has not met with practical success. U.S. Pat. No. 5,052,256 to Morrissey and U.S. Pat. No. 4,951,540 to Cross et al disclose designs that perform only one specialized cut on only one type of shingle. Considered analysis indicates that in addition to this limitation these two designs do not allow the user to develop sufficient leverage to operate successfully under the wide range of field conditions previously mentioned. 
     A different apparatus is disclosed in U.S. Pat. No. 5,787,781 to Hile. In the initial stages of my own experimentation, I developed, constructed, and tested a model essentially similar to this and determined that it has several shortcomings. The blade does not consistently maintain tight contact with the edge of the work surface because of lack of sufficient rigidity both of the blade and of the pivot arrangement. A very small amount of distortion in the area of the pivot allows the blade to separate from the edge of the work surface and merely sandwich the shingle between the two instead of cutting it. This phenomenon is exacerbated by the accretion of tarry deposits on the mating surfaces of the blade and the edge of the work surface as well as the accumulation of shingle debris and detached surface granules in these deposits and in the pivot area. 
     Use of a precision bearing as proposed by Hile has a drawback in that it will be vulnerable to damage in the real-world conditions that prevail while roofing is being done. This type of work is frequently carried out under wet conditions; also, the tendency of shingles to generate debris particles and shed granules as previously mentioned will degrade a precision mechanism. Moreover, the need for a complex bearing in this application is questionable, since the motion anticipated is comparatively slow and sporadic and covers something less than a ninety degree arc, whereas a ball or roller bearing would be more appropriately specified in an application having greater or continuous motion and/or higher speed. 
     Hile shows no method of sharpening the stationary cutting edge. As the edge becomes worn, the tendency of the shingle to be sandwiched between the cutting edge and the blade will increase. 
     Another shortcoming of Hile derives from the position of the guide member relative to the shingle. Since the shingle resists being cut, the motion of the blade tends to force the shingle to slide away from the pivot, and therefore, away from the guide member at the beginning of the cutting stroke. This reduces the accuracy of the cut. The Hile apparatus also lacks the ability to make an accurate and repeatable angle cut. Further, there is no provision at all to produce the lengthwise cuts that are necessary for the lowest, or starting course of shingles. 
     Hile proposes the blade to be outside of the footprint outlined by the supporting legs. This may allow the apparatus to tip to the right in response to vigorous force on the handle. In addition, the fact that the handle extends substantially beyond the ends of the legs would tend to cause the opposite, or pivot, end of the apparatus to lift in response to the cutting stroke. Further, the apparent width between the legs of the apparatus would seem to preclude its use on the narrow scaffolding typically used on a roof. 
     SUMMARY 
     In accordance with the present invention, a shingle cutting apparatus comprises a raised work surface with a horizontal fixed blade attached along one side, a moveable and adjustable blade assembly, and a guide fence assembly capable of being fixed at any desired location on the work surface to align a shingle for a cut. 
     OBJECTS AND ADVANTAGES 
     Accordingly, several objects and advantages of my invention are as follows: 
     1. The triangular design of the moveable blade assembly, the use of a long pivot shaft attached on both ends, and the design of the frame all provide superior rigidity and keep the moveable and fixed blades in tight contact with each other resulting in clean shearing action. Adjustment is provided to maintain this relationship and to compensate for wear and sharpening. 
     2. The moveable blade is prevented from distorting by the combination of the blade brace and the triangular web between them that together form a rigid blade assembly. 
     3. The use of a vertical moveable blade and a horizontal, protruding fixed blade minimizes tarry buildup since the fixed blade acts as a scraper to keep the moveable blade substantially clean. Since this buildup occurs mainly on wide surfaces, the edge of the fixed blade also remains substantially clean. 
     4. The use of a fixed blade that protrudes beyond the side of the work surface provides clearance for the shingle cutoff, or waste piece, to curl downward during the cut and fall away without dragging on the side of the work surface, which would force the shingle out of position during the cutting stroke. 
     5. The use of a moveable guide fence permits accurate and repeatable angled or ninety degree cuts. A detent arrangement provides a positive stop for ninety degree cuts. 
     6. With the guide fence supporting the edge of the shingle furthest from the pivot shaft, the shingle is prevented from sliding in response to the action of the blade. In my apparatus the action of the blade tends to hold the shingle more securely against the guide fence. 
     7. The guide fence is easily repositioned on the work surface to permit length-wise cutting of shingles. A detent arrangement positively locates the guide fence parallel to the blades and automatically produces proper width cut pieces in accordance with the several standard dimensions used by shingle manufacturers. 
     8. The design of the pivot shaft minimizes the accumulation of shingle debris land granules that would inhibit proper operation of the moveable blade. The open end of the blade tube extends under the protruding fixed blade to deflect falling debris. More importantly, there is no precision ball or roller bearing mechanism that would be vulnerable to infiltration of debris as well as inflitration of moisture which would create rust. By eliminating a precision bearing, a potential maintainance problem due to rust or contamination is avoided and the apparatus will be simplified. 
     9. The design of the rear leg enables the user to anchor the device with his or her foot while operating the apparatus if desired. At the same time, the user&#39;s foot is protected from injury since it is shielded by the raised frame. 
     10. The overall shape of the frame assembly is conducive to use on a scaffolding as well as on the roof surface. A leg arrangement providing three points of support results in stability of the apparatus while in use. 
     11. The handle of the moveable blade does not extend significantly rearward of the footprint outlined by the three points of support of the base assembly. This avoids destabilizing of the apparatus when making a cut. The fact that the blades are laterally within this footprint keeps the apparatus from tipping to the right during operation. 
    
    
     Further objects and advantages of my invention will become apparent from a consideration of the drawings and subsequent description. 
     DESCRIPTION OF THE DRAWINGS 
     In the drawings, closely related figures have the same number but different alphabetic suffixes. 
     FIG. 1 shows a shingle cutting apparatus with the moveable blade assembly in an open position and the guide fence assembly located for angled cutting. 
     FIG. 2 shows the apparatus with the blade assembly in a closed position and the guide fence assembly located for lengthwise cutting. 
     FIG. 3 shows the frame assembly. 
     FIGS. 3A and 3B are cross sections of the frame assembly. 
     FIG. 4 shows the guide fence assembly. 
     FIG. 4A is a cross section of the guide fence assembly. 
     FIG. 5 shows the moveable blade shaft assembly. 
     FIG. 5A is a cross section of the moveable blade assembly and moveable blade shaft 
     FIG. 6 is a partial view of the moveable blade assembly showing the blade tube extension. 
     FIG. 7 shows an alternate method of adjusting the blade shaft assembly. 
     FIGS. 8A,  8 B, and  8 C are schematics showing the positions of shingles while being cut. 
     FIG. 9 shows a partial cross section of the moveable blade assembly, the blade shaft assembly, and washer in an alternate embodiment using a spring. 
     FIG. 10 shows a partial view of the crossbar, the shaft mounting bracket, the washer, and moveable blade assembly in the alternate embodiment with the spring. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 REFERENCE NUMERALS IN DRAWINGS 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10. 
                 Frame assembly 
               
               
                   
                 11. 
                 Fixed blade support rail 
               
               
                   
                 12. 
                 Fixed blade 
               
               
                   
                 13. 
                 Screw 
               
               
                   
                 14. 
                 Semicircular rail 
               
               
                   
                 15. 
                 Guide fence locating plate 
               
               
                   
                 16. 
                 Crossbar 
               
               
                   
                 17. 
                 Crossbar brace 
               
               
                   
                 18. 
                 Front leg 
               
               
                   
                 19. 
                 Rear leg 
               
               
                   
                 20. 
                 Rear leg extension 
               
               
                   
                 21. 
                 Resilient foot 
               
               
                   
                 22. 
                 Blade stop 
               
               
                   
                 23. 
                 Guide fence anchor pin hole 
               
               
                   
                 24A. 
                 Guide fence anchor pin hole 
               
               
                   
                 24B. 
                 Guide fence anchor pin hole 
               
               
                   
                 25. 
                 Detent hole 
               
               
                   
                 26A. 
                 Detent hole 
               
               
                   
                 26B. 
                 Detent hole 
               
               
                   
                 27. 
                 Shaft bracket bolt hole 
               
               
                   
                 28. 
                 Blade shaft hole 
               
               
                   
                 30. 
                 Guide fence assembly 
               
               
                   
                 31. 
                 Guide fence 
               
               
                   
                 32. 
                 Anchor pin 
               
               
                   
                 33. 
                 Clamp bolt 
               
               
                   
                 34. 
                 Washer 
               
               
                   
                 43. 
                 Moveable blade shaft 
               
               
                   
                 44. 
                 Shaft washer 
               
               
                   
                 45. 
                 Shaft lock nut 
               
               
                   
                 46. 
                 Shaft mounting bracket 
               
               
                   
                 47. 
                 Mounting bracket hole 
               
               
                   
                 48. 
                 Mounting bracket bolt 
               
               
                   
                 49. 
                 Flat washer 
               
               
                   
                 50. 
                 Shim 
               
               
                   
                 51. 
                 Nut 
               
               
                   
                 54. 
                 Moveable blade assembly 
               
               
                   
                 55. 
                 Blade 
               
               
                   
                 56. 
                 Cutting edge 
               
               
                   
                 57. 
                 Cutting edge mounting screw 
               
               
                   
                 58. 
                 Blade brace 
               
               
                   
                 59. 
                 Blade tube 
               
               
                   
                 60. 
                 Blade web 
               
               
                   
                 61. 
                 Handle support 
               
               
                   
                 62. 
                 Handle 
               
               
                   
                 63. 
                 Blade tube extension 
               
               
                   
                 69. 
                 Adjustment set screw 
               
               
                   
                 70. 
                 Spring 
               
               
                   
                 71. 
                 Shingle waste piece 
               
               
                   
                 72. 
                 Shingle piece desired 
               
               
                   
                 73. 
                 Line of cut achieved 
               
               
                   
                   
               
             
          
         
       
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A shingle cutting apparatus as shown in FIGS. 1-10 consists of a frame assembly  10 , including reference numerals  11  through  28 ; a guide fence assembly  30 , including reference numerals  31  through  39 ; a moveable blade shaft assembly  42  including reference numerals  43  through  51 ; and a moveable blade assembly  54  including reference numerals  55  through  63 . The several components are made of metal or other suitable material. 
     FRAME ASSEMBLY  10 : As shown in FIG. 3, frame assembly  10  has a fixed blade support rail  11 , a semicircular rail  14 , a guide fence locating plate  15 , a crossbar  16 , and a crossbar brace  17  that together provide a working surface for the shingle being cut. As shown by FIGS. 1 and 3, support rail  11  carries a fixed blade  12  secured by screws  13 . Fixed blade  12  may be made of mild steel, carbide steel, or other suitable material. FIG. 3A shows rail  11  to be of inverted L shape with blade  12  extending laterally to the right, overhanging rail  11 . FIG. 3B shows rail  14  also to be in the form of an inverted L having a surface to support guide fence assembly  30  and a lower rim to permit gripping by a clamp bolt  33 , seen in FIG.  4 . Again referencing FIG. 3, two front legs  18  and a rear leg  19  with a rear leg extension  20  support the apparatus at a convenient height above the surface on which it is used. Resilient feet  21  are provided to afford non-skid positioning of the apparatus and to protect the surface on which it is placed. A blade stop  22  is incorporated into frame assembly  10  to provide a positive limit to the downward cutting stroke. Guide fence anchor pin holes  23 ,  24 A, and  24 B are provided in plate  15  for the proper positioning of guide fence assembly  30 , shown in FIGS. 1,  2 , and  4 , in the locations needed for operation. Referring to FIGS. 3 and 4, hole  23  receives an anchor pin  32  on fence assembly  30  when an angled or a ninety degree cut is desired. Sufficient clearance is provided beneath plate  15  in the vicinity of hole  23  to permit unrestricted movement of the angled portion of pin  32  as it describes an arc in response to the repositioning of fence assembly  30  along rail  14 . Holes  24 A and  24 B receive pin  32  when fence assembly  30  is oriented for lengthwise cuts. A detent hole  25  engages a detent ball  39  on fence assembly  30  for alignment at a right angle to blade  12 . Detent holes  26 A and  26 B engage detent ball  39  when fence assembly  30  is oriented for lengthwise cutting. A shaft bracket bolt hole  27  is an elongated hole which receives a bolt  48  to attach a shaft mounting bracket  46 , shown in FIG. 5. A blade shaft hole  28  accepts the threaded end of a moveable blade shaft  43 , also shown in FIG.  5 . 
     GUIDE FENCE ASSEMBLY  30 : Guide fence assembly  30 , as shown in FIGS. 4 and 4A, has a guide fence  31  with L-shaped anchor pin  32  attached at one end. A clamp bolt  33 , a washer  34 , and a clamp knob  35  are installed in a clamp bolt housing  36  and designed such that tightening knob  35  causes bolt  33  to grip frame rail  14 , and at the same time force the angled portion of anchor pin  32  to contact the underside of plate  15  as shown in FIGS. 1 and 2. FIG. 4A shows a cross section of guide fence assembly  30  taken at the location of detent ball  39  and a detent spring  38  captive in a detent bore  37 . Detent ball  39  engages holes  25 ,  26 A, or  26 B on frame rail  14  depending on the positioning of guide fence assembly  30 . 
     MOVEABLE BLADE SHAFT ASSEMBLY  42 : FIG. 5 shows moveable blade shaft assembly  42 , which attaches to frame assembly  10  by means of holes  27  and  28 . After passing through a washer  44  and a blade tube  59  of moveable blade assembly  54 , a moveable blade shaft  43  is inserted through hole  28  and secured with another washer  44  and a shaft lock nut  45 . FIG. 5A shows a cross section of the assembled positions of these parts. Shaft asembly  42  is further secured through a hole  47  in a shaft mounting bracket  46  by a bolt  48 , two washers  49 , and a nut  51 . One or more shims  50  are provided to adjust the position of blade assembly  54 . 
     MOVEABLE BLADE ASSEMBLY  54 : Moveable blade assembly  54  is shown in FIGS. 1,  2 , and  6  and in cross section in FIG.  5 A. An elongate support arm  55 , supporting a blade  56 , is attached to a blade brace  58  and a blade tube  59  and is maintained substantially straight and rigid by a blade web  60 . Blade tube  59  is cylindrical in shape and large enough in inside diameter to preclude contact with shaft  43 . A blade tube extension  63 , seen in FIGS. 5A and 6 reaches under rail  11  and blade  12 . The only points of contact between shaft  43  and blade assembly  54  are where the shaft passes through holes in arm  55  and brace  58 . A handle support  61  connects a handle  62  to blade assembly  54 . Blade  56  is detachably secured to arm  55  with mounting screws  57 . Blade  56  may be either curved as shown or straight and may be made of mild steel, carbide steel, or other suitable material. 
     ASSEMBLY OF THE COMPONENTS: When installed according to the previous description, blade assembly  54  is maintained in firm contact with fixed blade  12  by tightening lock nut  45  while mounting bracket  46  is loosely attached to crossbar  16 . Since hole  27  is elongated, blade assembly  54  is free to move laterally in response to the tightening of lock nut  45 . One or more shims are then inserted between mounting bracket  46  and crossbar  16 , as shown in FIG. 5, to bring the handle end of blade assembly  54  into tight contact with the corresponding end of fixed blade  12 . By varying the setting of lock nut  45  and the number of shims  50  used, blade  56  can be made to slide across fixed blade  12  with sufficient tension to remain in contact during use but not so tight as to inhibit the movement of blade assembly  54 . Once the proper number of shims has been inserted, bolt  48  and nut  51  are tightened, thereby maintaining the adjustment. This sequence will be repeated when final blade  12  and moveable blade  56  are replaced or sharpened. 
     Referring to FIGS. 1 and 4, guide fence assembly  30  is installed by tilting it to enable anchor pin  32  to be inserted in hole  23  and then engaging clamp bolt  33  at the desired location on rail  14 . Tightening clamp knob  35  secures fence assembly  30  in place. By loosening clamp knob  35 , the fence assembly may be pivoted to any desired location on rail  14  without removal. Detent ball  39  engages detent hole  25  to orient fence assembly  30  for right angle cuts. Use of holes  24 A and  26 A, or alternatively, holes  24 B and  26 B, allows positioning of fence assembly a  30  for lengthwise cuts as needed. Clamp bolt  33  secures fence assembly  30  in these locations as well, as shown in FIG.  2 . 
     ALTERNATIVE EMBODIMENTS 
     As shown in FIG. 7, an alternate means of adjusting moveable shaft assembly  42  is with the use of threaded set screws  69  in lieu of shims  50 . In this embodiment, the assembly and adjustment sequence is analagous to the preferred embodiment except for this substitution. The adjusting of the set screws  69  takes the place of the function of the shims. FIGS. 9 and 10 show another embodiment, utilizing a spring  70  disposed on shaft  43  that takes the place of shims  50  or set screws  69 . In the assembly of this embodiment, lock nut  45  is tightened as previously detailed and spring  70  automatically provides the adjustment function that is manually achieved in the other embodiments described. 
     OPERATION 
     The present invention can be used on the ground, on scaffolding, or on the roof itself. FIGS. 8A-C indicate the juxtapositioning of shingles on the apparatus. Those reference numerals that are not indicated in FIGS. 8A-C are shown in FIGS. 1 through 4. FIG. 8A shows guide fence assembly  30  configured for making an angled crosscut on a shingle. For this type of cut, anchor pin  32  is located in hole  23  on plate  15 . With clamp knob  35  loose, fence assembly  30  is pivoted to the desired angle. Knob  35  is then tightened, engaging the lower edge of rail  14  and at the same time causing anchor pin  32  to contact the underside of plate  15 , effectively locking fence assembly in position. The user then grasps the handle  62  and raises blade assembly  54 . The shingle is inserted against fence assembly  30  and positioned over fixed blade  12  at the appropriate point to produce the desired size cut piece. The user brings blade asembly  54  downward, shearing the shingle, creating a desired cut piece  72  and a waste piece  71 . FIGS. 8A-C indicate the outline of the visible portions of the shingles with a dot-dot-dash line and that portion of waste piece  71  that is beneath blade assembly  54  by a dotted line. If a right-angled cut is needed, clamp knob  35  is loosened and fence assembly  30  is rotated along rail  14  until detent ball  39  engages hole  25 . Knob  35  is then tightened and cutting proceeds as above. 
     FIGS. 8B and 8C show the two-step cutting process to produce a lengthwise cut. First, fence assembly  30  is detached by loosening knob  35  until clamp bolt  33  can be completely disengaged from rail  14 . Fence assembly  30  is tilted forward to allow anchor pin  32  to be removed from hole  23 . Anchor pin  32  is then inserted in hole  24 A or  24 B in plate  15 , depending upon the width of cut piece  72  that is desired. Detent ball is then engaged in hole  26 A or  26 B respectively and clamp bolt  33  is secured under rail  14  by tightening knob  35 . Holes  24 A and  26 A are used in concert, as are holes  24 B and  26 B. Due to the length of the shingle, the cut will be made in two passes. Blade assembly  54  is raised, the shingle is inserted along fence assembly  30  as far into the blade as it will go, as represented in FIG. 8B, and the cutting stroke is made. The shingle will be cut somewhat more than halfway along, and the waste piece  71  will fall away to the extent that it has been cut. Blade assembly  54  is then raised. The shingle is then advanced into the blade. Shingle piece desired  72  will slide forward over the front end of frame assembly  10  and waste piece  71  will slide forward under crossbar  16 . This position is represented in FIG. 8C. A second stroke of the blade is now made, completing the cut. If desired, the user may brace the apparatus with his or her foot placed on leg extension  20  for additional stability. 
     The method of adjusting blade tension is described in detail in the section ASSEMBLY OF THE COMPONENTS under the heading DESCRIPTION OF THE PREFERRED EMBODIMENT. 
     CONCLUSIONS, RAMIFICATIONS, AND SCOPE 
     By utilizing rigidly designed frame and moveable blade assemblies, cutting action is efficient and not hampered by distortion of the apparatus. The adjustability incorporated into the blade assembly mounting system, previously detailed, allows the crisp cutting action to be maintained in the face of variables such as sharpening and wearing of the blades. The overall size and shape of the apparatus make it convenient to use. 
     The apparatus is designed to tolerate a hostile working environment. It will not be negatively affected by limited exposure to wet weather on a construction site. The open design of the working surface as well as the protective extension of the blade tube tend to prevent shingle granules and debris from accumulating and hindering operation. The avoidance of any type of precision bearing in favor of a simpler design is further recognition of the adverse effects of moisture and debris infiltration. 
     The versatility of the guide fence design permits cuts of any orientation to be made quickly and easily. The overall configuration of the apparatus renders it stable in use, and thus safe for the operator. The overhanging fixed blade provides clearance for the shingle waste piece to fall away cleanly, and not drag on the side of the frame to force the shingle out of position during the cut. 
     While my foregoing description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as an exemplification of one preferred embodiment thereof. Other variations are possible, for example: 
     1. Referencing FIGS. 9 and 10, means to maintain tension between moveable blade assembly  54  and fixed blade  12  may comprise a spring  70  on blade shaft  43  in lieu of shims  50  or set screws  69 . 
     2. Fixed blade  12  and cutting edge  56  can be made integral with their respective assemblies, rather than detachable as shown in FIGS. 1 and 3. 
     3. Blade web  60  may be made of perforated or expanded mesh material to save weight, rather than the solid material shown in FIG.  2 . 
     4. Rear leg extension  20  may be eliminated for simplicity. 
     5. Threaded set screws  69  may be substituted for shims  50  shown in FIG.  5 . This alternate embodiment is shown in FIG.  7 . 
     6. Frame rail  14  may be inscribed with radial markings and numerals indicating angular degrees for reference in positioning guide fence assembly  30 . Fence assembly  30  may likewise be inscribed with length markings and numerals to assist in positioning the shingle being cut. 
     7. Blade tube extension may be eliminated for simplicity. 
     8. Detent ball  39 , spring  38 , and bore  37  may be eliminated for simplicity. If this is done, holes  25 ,  26 A and  26 B would likewise be eliminated. 
     9. The semicircular area between rail  14  and rail  11  may be filled in with perforated, mesh, or solid material. 
     Accordingly, the scope of the invention should be determined not by the embodiment illustrated, but by the appended claims and their legal equivalents.