Patent Publication Number: US-2006016305-A1

Title: Apparatus for trimming a work piece

Description:
FIELD OF THE INVENTION  
      This invention relates in general to automated machinery for cutting work pieces and in particular to an apparatus for automatically trimming an end portion of a piece of lumber to a predetermined angle that may be used as a member in a roof truss.  
     BACKGROUND OF THE INVENTION  
      Automated sawing machines and systems are well known and available for a wide range of applications. For example, there are many types of computer-controlled sawing systems that cut lumber into prescribed lengths and at various angles according to a cut list programmed or entered into the computer. Many wood structures are fabricated from components that are cut to various lengths using automated sawing machines with each component&#39;s end portions being cut at various angles. This allows for two or more components to be more easily joined together where they intersect with one another at different angles. For example, the web and chord components of wooden trusses are often cut and pre-assembled at a fabrication facility then transported to a construction site for roof structures. Other examples are known in the art.  
      Various sawing apparatuses are disclosed in U.S. Pat. No. 4,098,310 to Sanford et al., U.S. Pat. No. 4,100,949 to Carter, U.S. Pat. Nos. 4,454,794 to Thornton and 4,545,274 to Germond for cutting truss members at predetermined lengths and angles. Carter discloses a machine for forming beveled webs that employs a reciprocable board-severing saw and a pair of electric motors for cutting bevels in the ends of the webs. The motors are mounted to a frame that also supports components for performing other cutting operations.  
      Thornton discloses another apparatus for cutting bevels or compound angles in the end of a truss member. Thornton discloses an apparatus that makes the compound angle cuts by traversing a power-driven circular saw blade in one direction along a linear guide way with the saw blade at a first angle followed by traversing the saw blade in a second direction along the linear guide way at a second angle to produce the second cut. Similar to the device of Carter, the apparatus used for cutting bevels of Thornton are mounted to a frame that also supports components for performing other cutting operations.  
      It is also known in the art to cut the ends of truss members individually by hand using a power saw to form various angles for joining respective truss members. This is particularly true in those truss-fabricating facilities that are not highly automated but are more labor intensive. Cutting the truss members in this manner is a multi-step process that is prone to human error and may not meet the rate of production requirements desired by the fabrication facility.  
     BRIEF SUMMARY OF THE INVENTION  
      Embodiments of the invention provide a stand-alone, portable apparatus configured for repetitively and accurately cutting the ends of truss members to preset angles. Embodiments allow for an electric motor to be mounted on a carriage for translating the motor between an upper first position and a lower second position with respect to the work piece being cut or trimmed. The carriage may be set at a desired angle so that when the end of a truss member is inserted horizontally within a guide means the carriage angle will equal a desired angle of cut with respect to the end of the truss member. Different types of cutting blades may be attached the motor&#39;s shaft such as a pair of router heads mounted to form a V-shaped cutting groove. This allows for cutting bevels in the end of the truss member at the angle defined by the carriage in one cutting pass.  
      Embodiments of the invention may be automated or computer-controlled so that when an operator inserts an end of a truss member into the housing or frame a first mechanical switch may be activated to initiate a cutting cycle. The guiding means may horizontally guide the truss member toward the first mechanical switch and into a trimming position. A cutting cycle begins with movement of the carriage from the upper first position toward the lower second position. A first proximity switch may detect the carriage in its upper first position. When the carriage moves away from the first proximity switch a means for securing the truss member in the trimming position may be activated. On completing a cut a second proximity switch may be activated indicating the carriage has reached the lower second position. Activation of the second proximity switch may initiate the carriage&#39;s translation back to the first position to complete the cutting cycle. On the carriage&#39;s return to the upper first position the first proximity switch may be activated to release the securing means so the truss member may be removed from the housing. Testing has shown that the rate at which the ends of truss members are trimmed may increase from about six per minute using known techniques to about fifteen per minute using embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be more apparent from the following description in view of the drawings that show:  
       FIG. 1  is a perspective view of an embodiment of the invention.  
       FIG. 2  is a partial perspective view of the embodiment of  FIG. 1 .  
       FIG. 3  is a side view of the embodiment of  FIG. 1  with a portion of a housing broken away.  
       FIG. 4  is a top view of the embodiment of  FIG. 1  with a top housing removed.  
       FIG. 5  is a perspective view of a truss member having an end cut.  
       FIG. 6  is a perspective view of a truss member having an end cut.  
       FIG. 7  is a perspective view of a truss member having an end cut.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 1  illustrates an exemplary embodiment of the invention  10  comprising a top housing  12  and a bottom housing or frame  14  both of which may be fabricated of 12-gauge steel with frame  14  encasing an internal support frame  13 . A bin (not shown) for catching woodchips may be located beneath frame  14 . Handles  16  may be used to lift top housing  12  away from the bottom housing  14  via a hinge  18 . A pneumatic regulator or control device  20  may be provided for operating components of the invention as described below. Device  20  may include a connector  21  for receiving an air supply through a connected air supply line (not shown), a water separator  22  for removing water from the air supply and an oiler  23  for supplying oil to a pair of pneumatic valves  64  described below. A connector  24  may be provided for supplying air to valves  64  through an air supply line (not shown) and an air pressure gauge  25  may be used for monitoring air pressure within device  20 .  
       FIG. 2  illustrates a partial view of an exemplary embodiment of the invention comprising a manual turning crank  30  that may be used as part of a means for adjusting the angle of a carriage  32  shown in  FIGS. 3 and 4 . In an embodiment carriage  32  may be rotatably mounted to frame  14  about a pivot axis  34  so that carriage  32  may be adjusted between horizontal and vertical positions as indicated by arrow B in  FIG. 3 . In an alternate embodiment the means for adjusting may be computer-controlled such that an operator may enter the desired cut angle into a control processor or the cut angle may be programmed into the processor as part of a cut list. Embodiments of the invention may be used with other computer-controlled cutting machines such as the one disclosed in U.S. Pat. No. 6,615,100, which is incorporated herein by reference in its entirety. An indicator  36  may be provided indicating the carriage&#39;s  32  angle with respect to the horizontal. Indicator  36  may have an aperture  38  formed therein so that a scale  40  in degrees is visible to an operator indicating the carriage&#39;s  32  angle. This angle may define a cutting path angle as carriage  32  is translated from an upper first position to a lower second position during a cutting cycle.  
      Referring again to  FIG. 2 , a guide plate  35  may be affixed to frame  14  and include an upper flange  37  on which a work piece may be placed for an operator to set the cutting path angle. For example, the work piece may be a wooden truss member having an end cut at an angle, as shown in  FIG. 5 , such as a 45° angle. An operator may set the cutting path angle by ensuring that a lower edge  39  of indicator  36  fits flush against the angled cut when the member is placed on an edge on flange  37 . This ensures that the cutting path angle is the same or substantially the same as the angled cut in the end of the work piece.  FIG. 2  also illustrates a set of switches that may include a power on switch  41 , a power off switch  42  and a manual override switch  43 . Switch  43  may allow an operator to manually operate carriage  32  through one cutting cycle. An emergency stop switch (not shown) may also be provided.  
       FIG. 3  illustrates an exemplary embodiment of the invention with a portion of top housing  12  and bottom housing or frame  14  broken away to show carriage  32 . Carriage  32  may be supported within an undercarriage  33  affixed to an upper frame  35 . Upper frame  35  may be rotatably mounted within frame  14  about pivot axis  34 . The undercarriage  33  and carriage  32  may rotate with upper frame  35  about pivot axis  34 , which may comprise a pair of respective steel axels located between outer edges of upper frame  35  and frame  14  as best shown in  FIG. 4 . In  FIG. 3 , a portion of upper frame  35  is broken away to show an electric motor  50  that may be attached to carriage  32  such as by support mounts  52 , for example, or other appropriate means. Motor  50  may be a 5-HP, 3600-RPM electric motor designated as a NEMA 184T frame. A variable frequency device, such as one commercially available from AC Tech may be used for operating motor  50  at approximately 100 Hz. A cutting tool  54  may be mounted on a shaft  56  of motor  50  and in an embodiment cutting tool  54  may comprise a pair of router blades  57  that are mounted in reverse orientation to form a V-shaped cutting groove. Blades  57  may be conventional stock blades that are approximately 1″ wide, 3-toothed shaper heads for cutting 45° angles. Cutting tool  54  may be used to cut or trim a variety of composite materials and in an embodiment may cut the end portion of a truss member to form a compound angle as more fully described below.  
       FIG. 4  shows an embodiment of the invention with top housing  12  removed for ease of illustration. Means may be provided for reciprocally controlling the linear movement of the carriage  32  between an upper first position and a lower second position. Carriage  32  may be a support plate on which motor  50  may be mounted. It may be moved or translated within undercarriage  33  by means of guide rails  62  formed on respective ones of a pair of air cylinders  64 . Cylinders  64  may have approximately a 10″ run and may be ones commercially available from Rexroth. A pair of carriage guides  63  may matingly engage respective ones of the guide rails  62  for guiding carriage  32  reciprocally along cylinders  64 . Cylinders  64  may be actuated through an air hose connection  66 , which may interconnect cylinders  64  with pneumatic controller  20 . Controller  20  may be interconnected with an appropriately sized compressor.  
      The means for controlling movement of carriage  32  may include a controller or control processor  70  that actuates a pair of pneumatic valves  71  that drive air cylinders  64 . Valves  71  may be ones commercially available from Rexroth that include a single electrical solenoid and may actuate air cylinders  64  in response to a commercially available first mechanical switch  72  being activated. Switch  72  may be depressed and activated by the end of work piece  60 , which may be a truss member, when inserted into frame  14  for trimming. Switch  72  may be located on the underside of a bar or bracket  73  that moves or translates in fixed relation with carriage  32  during a cutting cycle. Bracket  73  may rotate with carriage  32  about pivot axis  34  so that the angle of the bracket matches the angled cut in the inserted end of work piece  60 . In an embodiment switch  72  may be offset from the center of the inserted end of work piece  60  so that a lateral edge of the end activates switch  72 . For example, when carriage  32  is in its upper first position switch  72  may be horizontally aligned with work piece  60  so that when the end of the work piece is inserted within frame  14  a lateral edge of the end will abut switch  72 . This activates switch  72  and initiates movement of carriage  32  from the upper first position toward the lower second position. When carriage  32  and bracket  73  move toward the lower second position switch  72  will move off the end of work piece  60  as it moves with carriage  32  thereby releasing the switch.  
      The means for controlling movement of carriage  32  may include a first inductive proximity switch  74  for detecting the upper first position of carriage  32  and a second inductive proximity switch  75  for detecting the lower second position of carriage  32 . First and second positions of carriage  32  may be detected when switches  74 ,  75  detect a metal flag or indicator  76  that may be affixed to bar  73 . These switches may be interconnected with controller  70  via respective connections  77 . When a work piece  60  is guided into its trimming position the inserted end may activate switch  72  by pressing the work piece end against the switch. This may signal controller  70  and pneumatic controller  20  through appropriate relays to actuate air cylinders  64 , which initiates linear movement of carriage  32  from the upper first position toward the lower second position to perform a cut. Second proximity switch  75  may detect flag  76  when carriage  32  is in the lower second position after the cut is complete as shown in  FIG. 4 . This may signal controller  70  and pneumatic controller  20  through appropriate relays to actuate air cylinders  64  for returning carriage  32  to the upper first position thereby completing one cutting cycle. First proximity switch  74  may detect flag  76  when carriage  32  is in the upper first position. Controller  70  may be configured so that another cutting cycle is not initiated when switch  74  is detecting flag  76  until switch  72  is again activated or an operator activates a manual override control by depressing override switch  43 . Controller  70  may include a 24-volt DC power supply and appropriate breakers. Alternate means for reciprocally controlling linear movement of carriage  32  will be recognized by those skilled in the art and may include electrically or hydraulically driven mechanisms, for example. In alternate embodiments the means for controlling movement of carriage  32  may be computer-controlled rather that switch activated. For example, embodiments of the invention may be used with other computer-controlled cutting machines such as that disclosed in U.S. Pat. No. 6,615,100 whereby the control processor of that cutting machine controls the movement of carriage  32  to complete a cutting cycle.  
      A means for guiding work piece  60  into a trimming position may be provided. The guiding means may be an appropriately sized channel  82  defined by a metal frame  83  within which work piece  60  may be inserted and horizontally guided within frame  14  so that an end may activate switch  72 . The guiding means may be sized to guide an end a wooden truss member having a standard width dimension of approximately 2″ with varying heights of between about 2″ to 6″. The guiding means may be sized so the truss member is standing on an edge when in the trimming position. In this respect, router blades  57  may be sized to accommodate the approximate 2″ width of a truss member  60  to make a pair of compound bevel or other cuts in the end portion. Alternate embodiments allow for different sized and shaped cutting tools  54  to be used for varying sizes of work pieces  60 .  
      In an embodiment of the invention a means for securing work piece  60  in fixed relation to frame  14  when trimming the end may be provided. Referring to  FIG. 4 , the securing means may be a pneumatically actuated plunger or clamping cylinder  80  mounted to frame  83  that is interconnected with pneumatic controller  20  via connections  85 . Cylinder  80  may have approximately a 1″ throw and may be one commercially available from Rexroth. It may be activated when flag  76  moves off of first proximity switch  74  when carriage  32  begins a cutting cycle. When cylinder  80  is actuated it may push work piece  60  against a support surface of frame  83  and secure it in place while a cut is being performed. An end portion of cylinder  80  may have a textured surface for gripping work piece  60  to prevent it from slipping during a cut. When switch  74  detects flag  76  when carriage  32  returns to the upper first position cylinder  80  may be deactivated so work piece  60  may be removed from guide means  82 . Alternate means for securing work piece  60  may be used such as ones that are electrically or hydraulically actuated, for example.  
      As may be appreciated from  FIGS. 3 and 4 , an embodiment allows for carriage  32  to translate along a linear cutting path or direction indicated by arrow A in  FIG. 3 . Carriage  32  may translate from an upper first position, which may be above work piece  60  toward a lower second position, which is a position sufficient for cutting tool  54  to traverse a dimension of work piece  60  to complete a cut, such as across a height of work piece  60  positioned within the guiding means. As carriage  32  translates along the cutting path, cutting tool  54  may descend and approach work piece  60  in a direction that is along the work piece&#39;s longitudinal or lengthwise axis. Cutting tool  54  may lie in a plane that is coplanar with a plane extending from the upper edge of work piece  60  as shown in  FIG. 4 . For example, if work piece  60  is a truss member it may be inserted horizontally into the guiding means on an edge as shown in  FIG. 4 . Carriage  32  may approach the horizontally positioned truss member at an oblique angle to the horizontal so that cutting tool  54  cuts a compound angle toward the end of the truss member that is oblique with respect to the truss member&#39;s longitudinal axis. The compound angle may include a first bevel  84  and a second bevel  86  shown in  FIG. 5  both of which may be cut in one continuous cutting motion as cutting tool  54  moves simultaneously in an X direction and a Y direction across the end of truss member. In this respect, the cutting path will have a slope of 1 when cutting a 45° angle in the end of work piece  60 .  
       FIG. 5  illustrates an end portion  88  of a truss member  60  having a bevel cut at about a 45° angle across its height. As mentioned above, mechanical switch  72  may be aligned with a portion of a lateral edge  89  of member  60  so that lateral edge  89  depresses switch  72  when member  60  is inserted into frame  14  into a trimming position. As can be appreciated from comparing the cuts shown in  FIGS. 5 and 6 , the lateral edge  89  is cut away when cutting tool  54  completes its cut thereby releasing switch  72 . Offsetting switch  72  from the center of member  60  ensures that switch  72  is not activated again when carriage  32  makes its return run to the upper first position.  
      The compound angle cut in the work piece  60  or truss member may be at an angle oblique to the length of the truss member such as a 45° angle with respect to the horizontal as shown in  FIG. 6 . This aspect is advantageous because it allows bevels  84 ,  86  to be made with an end cut at an oblique angle in one cutting or trimming motion whereas known devices typically make this type of cut with multiple cutting motions and/or movements of the work piece  60 .  FIG. 7  illustrates that a single bevel  90  may be cut at an oblique angle in the end of a truss member with an appropriately shaped cutting tool  54 . It will be appreciated that adjusting the angle of carriage  32  with respect to the horizontal will define the angle of cut or cutting path cutting tool  54  will make as it traverses a dimension of work piece  60  such as the piece&#39;s height.  
      Referring again to  FIG. 4 , the means for adjusting the angle of carriage  32  may comprise manual turning crank  30  that may be operatively connected via an ACME threaded gear  91  to a coupler  92  connected with shaft or axle  34 . Coupler  92  may be an appropriately configured plate responsive to turning crank  30  for correspondingly rotating carriage  32 . This allows an operator to adjust the angle of carriage  32  with respect to the horizontal to define the angle at which cutting tool  54  will approach work piece  60  in its trimming position. As carriage  32  changes its angle indicator  36  will correspondingly move to allow an operator to quickly determine the carriage&#39;s angle with respect to the horizontal. Alternate means for adjusting the angle of carriage  32  will be recognized by those skilled in the art and may include electrically, pneumatically or hydraulically driven mechanisms, for example, and may be located on the opposite side of frame  14 .  
      While the exemplary embodiments of the present invention have been shown and described by way of example only, numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.