Abstract:
A cutting tool head for a sheet material cutting machine has a pressure foot mounted by way of linear actuators operable to independently move the pressure foot vertically relative to an eccentric drive mechanism and a knife assembly of the tool head. The knife assembly includes a support shaft driven by the eccentric mechanism, a blade connected to the support shaft, and a splined shaft between the support shaft and blade The splined shaft slides in a splined bushing, and the eccentric mechanism drives reciprocating motion of the support shaft, the splined shaft, and the blade relative to the splined bushing. The splined bushing is rotatable to rotate the splined shaft and blade. A blade sharpener of the tool head has a sharpening disc backed by a magnetic disc to attract the blade into evenly distributed contact with the sharpening surface, and to retain metal shavings on the sharpening disc.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority of U.S. Provisional Patent Application No. 61/637,442 filed Apr. 24, 2012, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of machine tools for cutting fabric and other sheet materials, and more particularly to cutting tool heads for such machines. 
       BACKGROUND OF THE INVENTION 
       [0003]    Cutting tool heads according to known designs have an eccentric mechanism that drives reciprocating up-and-down motion of a knife assembly to perform cutting operations. The knife assembly typically includes a support shaft connected to the eccentric mechanism and a vertical blade connected to the support shaft. Known cutting tool heads also have a pressure foot for contacting the material being cut, wherein the blade extends through a knife opening in the pressure foot to engage the material. In designs of the prior art, the eccentric mechanism, knife assembly, and pressure foot are mounted on a support frame that is vertically movable relative to a main support carriage of the tool head by operation of an actuator. The pressure foot is mounted on the vertically movable support frame by spring-biased support rods such that the pressure foot is able to deflect vertically relative to the eccentric mechanism and knife assembly. To engage the pressure foot with the material, the entire support frame is lowered. Conversely, to disengage the pressure foot from the material, for example where the cutting tool head is commanded to travel to a different cutting location on the material, the entire support frame must be moved upward by a distance sufficient to bring the pressure foot out of contact with the material. Because the pressure foot is spring-biased toward a downward position, the vertical movement distance of the support frame needed to achieve clearance from the material must take into account the spring deflection and thus may be greater than a simple upward incremental movement away from the material. This arrangement is not optimal in terms of cut-time efficiency and power consumption. An example of a prior art cutting tool head in accordance with the forgoing description is found in U.S. Pat. No. 4,841,822. 
         [0004]    In cutting tool heads, it is desirable that the knife assembly be configured to allow the blade to rotate about its vertical axis relative to the support shaft coupled to the eccentric drive mechanism. For this purpose, it is known to fasten the blade to the lower end of a vertical hollow cylinder, and to insert a spherical bushing into the upper end of the cylinder, wherein the spherical bushing is connected to the eccentric mechanism via a flexible link. The cylinder is slidably received within a vertical guide sleeve having an internal grove that engages a protruding edge of a tang at the trailing end of the blade. The guide sleeve is supported in the cutting tool head by rotary bearings and a rotary drive is coupled to the guide sleeve. When the guide sleeve is rotated, its rotation is transmitted to the blade and the cylinder, which rotate relative to the spherical bearing. The rotary drive and guide sleeve are mounted on a fixed support plate of the cutting tool head, and the eccentric mechanism and knife assembly are mounted for vertical movement relative to the support plate. U.S. Pat. No. 3,955,458 illustrates this type of configuration. As may be understood, maintenance and repair are time consuming. The spherical bearing, which is subject to wear from operating cycles, is difficult to replace because it is within the cylinder. Lubrication of the cylinder for sliding within the guide sleeve is difficult because there is a lack of easy access. Moreover, changing the knife blade requires removal of the blade from within the lubricated interior of the guide sleeve, making the task messy and time consuming. 
         [0005]    Cutting tool heads that incorporate an abrasive blade sharpening element are also known. A drawback of known designs is that the blade, which is subject to deflection, does not have a uniform force distribution over its contact area with the abrasive surface, resulting in uneven sharpening and diminished cut quality. Another drawback is that the metal shavings from the blade are not contained and can become lodged in the cutting tool head. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention addresses the problems mentioned above while providing a compact, reliable tool head that is easy to maintain. 
         [0007]    In accordance with a first aspect of the present invention, an eccentric mechanism, a knife assembly, and a pressure foot are mounted on a support assembly by a slide plate for vertical movement as a unit relative to the support assembly, and the pressure foot is mounted on the slide plate by way of at least one linear actuator operable to move the pressure foot up and down independently relative to the eccentric mechanism and the knife assembly. 
         [0008]    In another aspect, the present invention provides an improved configuration for vertically guiding the knife assembly and rotating the knife blade. The knife assembly includes a support shaft drivably connected to the eccentric mechanism, a vertical blade connected to the support shaft, and a vertical splined shaft arranged between the support shaft and the vertical blade The splined shaft is slidably received by a splined bushing, and the eccentric mechanism drives reciprocating up-and-down motion of the support shaft, the splined shaft, and the blade relative to the splined bushing. The eccentric mechanism, the knife assembly, and the splined bushing are mounted on the support assembly for vertical movement as a unit relative to the support assembly, and the splined bushing is rotatable about a vertical axis relative to the support shaft to impart rotation to the splined shaft and the blade relative to the support shaft. 
         [0009]    In a further aspect, the invention provides a cutting tool head having improved means for sharpening a blade. The blade sharpening means includes at least one blade sharpening disc having a sharpening surface coated with abrasive material for contacting the blade and a magnetic backing disc behind the sharpening surface for magnetically attracting the blade to urge the blade into evenly distributed contact with the sharpening surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING VIEWS 
         [0010]    The invention is described in detail below with reference to the following figures: 
           [0011]      FIG. 1  is a perspective view showing an automated multi-ply cutting machine incorporating a cutting tool head in accordance with an embodiment of the present invention; 
           [0012]      FIG. 2  is a perspective view of the cutting tool head, wherein an external housing of the tool head is rendered transparent to reveal internal structure; 
           [0013]      FIG. 3  is a right side view of the cutting tool head without the housing; 
           [0014]      FIG. 4  is a left side view of the cutting tool head without the housing; 
           [0015]      FIG. 5  is a rear view of the cutting tool head without the housing; 
           [0016]      FIG. 6  is a top view of the cutting tool head without the housing; 
           [0017]      FIG. 7  is a front view of the cutting tool head without the housing, wherein a pressure foot assembly of the tool head is shown in an extended condition and a knife assembly of the tool head is shown in a raised home position; 
           [0018]      FIG. 8  is a view similar to that of  FIG. 7 , wherein the pressure foot assembly is shown in a compressed condition and the knife assembly is shown in a lowered cutting position; 
           [0019]      FIG. 9  is a view similar to that of  FIG. 7 , wherein a sharpening assembly is shown in sharpening engagement with a cutting blade mounted in the tool head; 
           [0020]      FIG. 10  is an enlarged perspective view of the sharpening assembly in sharpening engagement with a cutting blade mounted in the tool head; 
           [0021]      FIG. 11  is another enlarged perspective view of the sharpening assembly in sharpening engagement with a cutting blade mounted in the tool head; 
           [0022]      FIG. 12  is a perspective view of the sharpening assembly in isolation, wherein an outer housing of an indexing gear box of the sharpening assembly is rendered transparent to reveal internal structure; 
           [0023]      FIG. 13  is an enlarged perspective view showing a pair of sharpening wheels, an indexing gear box, and a rotary actuator of the sharpening assembly in isolation, wherein the outer housing of the indexing gear box is rendered transparent to reveal internal structure; 
           [0024]      FIG. 14  is a sectional view of the tool head showing the knife assembly; 
           [0025]      FIG. 15  is a perspective view of the knife assembly in isolation; 
           [0026]      FIG. 16  is a sectional view of the knife assembly in isolation; and 
           [0027]      FIG. 17  is an enlarged perspective view showing a coupling for removably mounting a cutting blade on the knife assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]      FIG. 1  shows an automated multi-ply cutting machine  1  for cutting fabric and other sheet materials. Cutting machine  1  includes a cutting table  2  straddled by a gantry  3  movable along the cutting table  2  in an X direction. The gantry  3  extends in a lateral Y direction of table  2  perpendicular to the X direction. A cutting head  10  formed in accordance with an embodiment of the present invention is mounted on gantry  3  for travel with the gantry, and is movable along the gantry laterally relative to table  2  in the Y-direction. Cutting head  10  is configured to hold tools, for example a cutting knife, a drill, and/or a marking pen, and to operatively engage the tools with fabric or sheet material present on table  2 . A computer with an operator workstation  4  is provided to enable cutting machine  1  to be programmed to cut or mark shapes and patterns from or on the fabric or sheet material. Software executed by computer  4  provides an operator interface to program and store jobs, and to run jobs by converting stored job parameters into motion commands controlling the X axis position of gantry  3 , the Y axis position of tool head  10 , the vertical Z axis position of a tool carried by tool head  10 , and tool reciprocating or rotary motion. 
         [0029]    Tool head  10  of the present invention is shown in  FIGS. 2-7 . Tool head  10  comprises an external housing  12  enclosing a support assembly  15  and gantry sleeve  16 . Gantry sleeve  16  receives gantry  3 , and a drive motor  17  mounted on support assembly  15  is connected to the gantry and is operable to displace tool head  10  along the gantry. A drill  13  is operable to protrude downwardly from housing  12  to engage material  5 . 
         [0030]    A cutting blade  11  extends vertically and is receivable through an opening in a pressure foot  14 . The cutting blade is part of a knife assembly that extends vertically through tool head  10 . The knife assembly includes a support shaft  18  near its upper end. Support shaft  18  is coupled by a rotary bearing  32  to an eccentric mechanism  20 , whereby rotational motion inputted to the eccentric mechanism results in a reciprocating up-and-down motion of the support shaft  18  and blade  11 . Eccentric mechanism  20  and the reciprocating knife assembly are carried by a slide plate  23  mounted for vertical travel relative to support assembly  15  by linear slide bearings  27  movable along vertical rails  26  fixed to support assembly  15 . Slide plate  23  is moved up and down by a linear actuator  25  visible in  FIGS. 3 and 4 . Slide plate  23  and linear actuator  25  are operable to move the knife assembly between a raised home position as depicted in  FIG. 7  and a lowered cutting position as depicted in  FIG. 8 . Linear actuator  25  may be pneumatically or electro-mechanically driven. 
         [0031]    Additional reference is made now to the sectional view of  FIG. 14 . The knife assembly extends through a pressure foot assembly generally indicated by reference numeral  28 . Pressure foot assembly  28  is rotatable about a vertical axis that coincides substantially with a line of action of the knife assembly. As will be described in greater detail below, the pressure foot assembly transmits its rotation to blade  11 . Pressure foot assembly  28  is mounted on slide plate  23  by a yoke  50 . Pressure foot assembly  28  includes pressure foot  14 , a pair of linear actuators  30 , a rotation sprocket  55 , a support cylinder  54  coupled to rotation sprocket  55  and rotatably mounted in yoke  50  by rotary bearings  53 , and a slip ring assembly  52 . A drive motor  22  mounted on yoke  50  is operable to rotate sprocket  55  and support cylinder  54  via a drive belt  24  engaged by a drive sprocket  56  on the output shaft of motor  22  and by an idler roller  57 . An upper portion of each linear actuator  30  is coupled to support cylinder  54  and a lower portion of each linear actuator  30  is coupled to pressure foot  14 , whereby rotation of sprocket  55  and support cylinder  54  is transmitted to pressure foot  14 . Linear actuators  30  are operable to move pressure foot  14  up and down relative to the knife assembly as can be seen by comparing  FIGS. 7 and 8 . 
         [0032]    The reciprocating knife assembly of the present invention will now be described in greater detail with reference to  FIGS. 14-17 . As mentioned above, the knife assembly has a rotary bearing  32  and a support shaft  18  that extends downwardly from rotary bearing  32 . A splined shaft  34  is connected to a lower end of support shaft  18  by a ball joint  33 . Splined shaft  34  is slidably received through a splined bushing  74  which is coupled to support cylinder  54  by a hub member  35 . As will be understood, the slidably mating splines of shaft  34  and bushing  74  permit the knife assembly to reciprocate vertically while also transmitting rotational motion of support cylinder  54  to the portion of the knife assembly below ball joint  33 . 
         [0033]    Blade  11  is removably mounted on the knife assembly by a collar assembly  80  located at a lower end of splined shaft  34 . Collar assembly  80  includes an inner clamp member  36  surrounded by an outer securement collar  37 . Clamp member  36  includes a stem portion  36 A extending upwardly into an axial opening at the lower end of splined shaft  34  and held in place by a transverse pin  39  arranged to extend through aligned openings in the shaft  34  and stem portion  36 A. Clamp member  36  further includes a main portion  36 B, a bottom flange  36 C, and a diametrical slot  36 D extending upwardly through bottom flange  36 C and partially through main portion  36 B. Slot  36 D is sized and configured to receive a shank portion  11 A of blade  11 . Shank portion  11 A may be retained in slot by a transverse pin  38  extending through aligned holes in main portion  36 B and shank portion  11 A. Main portion  36 B is generally cylindrical but has a flat side (not visible in  FIG. 17 ) to form a D-shaped profile. Securement collar  37  includes a corresponding D-shaped opening for  76  receiving main portion  36 B of clamp member  36 . Securement collar  37  has a radially enlarged portion  37 A, a radially reduced portion  37 B, and a bottom surface  37 C arranged to engage bottom flange  36 C of the clamp member. Securement collar  37  surrounds main portion  36 B, thereby preventing removal of pin  38 . Securement collar  37  has a first threaded hole  70  extending radially through enlarged portion  37 A for threadably receiving a first set screw  71  adjustable to press shank portion  11 A against a flat inner surface of D-shaped opening  76 . Securement collar  37  has a second threaded hole  72  extending radially through enlarged portion  37 A but offset angularly from first threaded hole  70  by ninety degrees for threadably receiving a second set screw  73  adjustable to engage main portion  36 B of clamp member  36 . Thus, second set screw  73  has a line of action transverse to slot  36 D, such that opposing prongs of main portion  36 B bifurcated by slot  36 D are forced toward an inner surface of D-shaped opening  76 . Tightening of set screws  71  and  73  eliminates play between blade  11  and the collar assembly  80  to securely attach blade  11  to the knife assembly. A flatted surface  36 E may be provided on clamp member  36  for engagement by second set crew  73 . 
         [0034]    As will be appreciated, the arrangement described above permits easy and safe replacement of worn blades. To replace blade  11 , set screws  71  and  73  are loosened and securement collar  37  is slid upward beyond pin  38  (one or both set screws may be adjusted to engage splined shaft  34  to temporarily maintain collar  37  above pin  38 ). Pin  38  is then displaced until it no longer retains shank  11 A, at which point blade  11  is removed from collar assembly  80 . The shank of a new blade may then be inserted into slot  36 D, collar  37  lowered to surround clamping member  36 , and set screws  71  and  73  tightened. Changeover to a new blade can be accomplished in about one minute, thus reducing job down time. The changeover location is spaced from lubricated bearings associated with reciprocating sliding motion of the knife assembly, thereby making changeover a much cleaner operation relative to prior art tool heads that required removal of the greased slide mechanism to change blades. 
         [0035]    Since the knife assembly may be driven at about 4,000 rpm, wear on the components is a concern. The knife assembly of the present invention is lightweight, thereby reducing stress. Most of the wear occurs at ball joint  33 , which experiences accelerations of about 300 G-forces during reciprocating motion. Ball joint  33  may be an inexpensive off-the-shelf part, such as Part No. RBI 6D from THK Co., Ltd., allowing economical stocking of spare parts and immediate replacement to avoid machine down time. 
         [0036]    A blade sharpening assembly  40  of the present invention will now be described in greater detail with reference to  FIGS. 9-13 .  FIG. 9  shows sharpening assembly  40  in operating position for sharpening blade  11 . Sharpening assembly  40  includes a pair of circular sharpening discs  42  each having a magnetic backing disc coated with an abrasive material for contacting blade  11 . During sharpening, the metal blade  11  is urged by magnetic force into flat engagement with sharpening discs, thereby avoiding the problem of blade deflection experienced in sharpening mechanisms of the prior art. An added benefit of magnetic discs  42  is that metal particles removed from blade  11  will adhere to the discs to keep pressure foot  14  free of debris; the metal particles may be removed from discs  42  simply by blotting the abrasive face of discs  42  with adhesive tape. 
         [0037]    Sharpening discs  42  may be rotatably mounted on an indexing unit  44  enabling the discs to be angularly indexed from time to time to expose an unused portion of the abrasive disc face to blade  11 . Indexing unit  44 , best shown in  FIG. 13 , may include a central drive gear  45  mated with a pair of follower gears  46 . Drive gear  45  may be driven by a pneumatic rotary actuator  48 . The number of degrees in the angular indexing steps may be chosen such that 360° is unevenly divisible by the indexing step in order to present an unused portion of the abrasive surface after each indexing step over multiple complete rotations of discs  42 . 
         [0038]    Sharpening discs  42 , indexing unit  44 , and rotary actuator  48  are carried by a forwardly extending support arm  82  mounted on slide plate  23  for laterally directed travel by a linear slide bearing  84  engaging a horizontal rail  86  fixed to a lower portion of slide plate  23 . Support arm  82  is movable along rail  86  by operation of a linear actuator  88  having one end fixed to slide plate  23  and another end connected to the support arm. Thus, sharpening discs may be selectively moved into an operating position to engage blade  11 , and the knife assembly may reciprocated up-and-down to sharpen the blade edge. The sharpening angle of the blade edge is adjustable by operating motor  22  to rotate pressure foot assembly  28  and the portion of the knife assembly including splined shaft  34 , collar assembly  80 , and blade  11 . Once sharpening is completed, linear actuator  88  is operable to move the sharpening discs  42  and indexing unit  44  out of the way. 
         [0039]    Embodiments of the present invention are described in detail herein, however those skilled in the art will realize that modifications may be made. Such modifications do not stray from the spirit and scope of the invention as defined by the appended claims.