Cutting machine having balanced reciprocating cutter drive mechanism
This is a continuation-in-part of co-pending application Ser. No. 094,823 filed on Sept. 9, 1987, abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates in general to reciprocating drive mechanisms for cutting machines and deals more particularly with an improved balanced reciprocating cutter drive mechanism of a crank type which has a rotary input and a reciprocating output. 
     The improved drive mechanism of the present invention is particularly adapted to operate with minimal vibration for reduced wear to prolong machine life and should find many uses. However, it is particularly well suited for driving the knife or blade of an apparatus for cutting pattern pieces from lay-ups of sheet material, and more specifically, a heavy duty, high speed, automatically controlled cutting machines of the aforedescribed type. Such cutting machines are manufactured and marketed by Gerber Garment Technology, Inc., Vernon, Conn., assignee of the present invention and may be provided with KNIFE INTELLIGENCE; a system which senses a cutting parameter affected by interaction of the cutting blade and the sheet material and provides feedback signals to alter the cutting path of the blade, as necessary, to compensate for any detected deviation from the predetermined cutting parameter. In a machine having such a sensing and control system, it is essential that the cutting blade operate smoothly and without excessive vibration, since vibration of the drive mechanism and the associated cutting blade can result in the generation of false signals by the KNIFE INTELLIGENCE system which adversely affect the cutting precision of the machine. 
     The present invention is concerned with the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention an improved dynamically balanced crank mechanism is provided for a machine having an angularly balanced crankshaft journalled for rotation about its shaft axis, an active load, means supporting the active load for reciprocal movement along one path, and first connecting means for connecting the active load to the crankshaft to reciprocate along the one path in response to rotation of the crankshaft. The improved crank mechanism comprises means for dynamically balancing the active load and the first connecting means and includes a passive load, means for supporting the passive load to reciprocate along another path, and second connecting means for connecting the passive load to the crankshaft to reciprocate along the other path and move in a direction generally opposite the direction of movement of the active load in response to rotation of the crankshaft about its shaft axis. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary side elevational view of a cutting machine embodying the present invention and shown partially in vertical section. 
     FIG. 2 is a somewhat enlarged fragmentary plan view of the machine shown in FIG. 1. 
     FIG. 3 is a fragmentary sectional view taken generally along the line 3,3 of FIG. 2. 
     FIG. 4 is a fragmentary sectional view taken along the line 4--4 of FIG. 1. 
     FIG. 5 is similar to FIG. 4, but shows the crankshaft in another position. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     Referring now to the drawings, the present invention is illustrated with reference to an automatic cutting machine indicated generally by the reference numeral 10 and having a balanced reciprocating drive or crank mechanism embodying the present invention and designated generally by the reference numeral 12. The cutting machine 10, which is illustrated somewhat schematically in FIG. 1, operates in response to signals received from a programmable controller 11 and is particularly adapted for cutting pattern pieces from various types of sheet material, such as woven and non-woven fabrics and plastic. The principal components of the machine include a support table having a support surface 14 on which a lay-up 16 of sheet material is spread, and a two-axis carriage mechanism indicated generally at 18 which includes an X carriage 20 supported to move longitudinally of the support table, in an X coordinate direction, and a Y carriage 22 carried by the X carriage and supported to move on and relative to the X carriage transversely of the support table, in a Y coordinate direction. A cutting apparatus indicated generally by the reference numeral 24 and mounted on the Y carriage to move with it includes an elongated blade 26 which has a cutting edge extending longitudinally of the blade. A connecting member 28, connected to the blade 26 through a universal joint 30, is slidably received within a sleeve bearing 32 which supports the connecting member and the blade for generally vertical reciprocating movement along a rectilinear path and relative to the support surface 14 and a lay-up of sheet material supported thereon, such as the illustrated lay-up 16. The blade 26 is further arranged to rotate about its longitudinal axis in directions indicated by the arrow θ in response to command signals from the controller 11 which controls operation of a reversible drive motor 36 for turning the blade about its axis. 
     The blade 26 is driven by the crank mechanism 12, which is drivingly connected to the connecting member 28 and will be hereinafter further described. The carriage assembly 18 moves in response to control signals received from the controller 11 to move the blade and the lay-up of sheet material on the support surface relative to each other and along a line of cut with the blade advancing in cutting engagement with the sheet material. A cutting machine of the aforedescribed type driven by a crank mechanism and having many of the features hereinbefore described is illustrated and described in U.S. Pat. No. 3,747,454 to Gerber, issued July 24, 1973, assigned to the assignee of the present invention, and hereby adopted by reference as part of the present disclosure. 
     The illustrated cutting machine 10 further includes a KNIFE INTELLIGENCE system indicated generally by the numeral 38 which has a sensing device 40 for detecting a cutting parameter that is affected by the interaction of the cutting blade and sheet material. Signals from the sensing device 40 are fed back in a closed loop automatic control mechanism to adjust or initiate further steps in the cutting operation whereby to maintain a predetermined line of cut. A more complete disclosure of a cutting apparatus having the aforedescribed feature is found in U.S. Pat. No. 4,133,235 to Gerber, issued Jan. 9, 1979, assigned to the assignee of the present invention, and hereby adopted by reference as part of the present disclosure. 
     Considering now the crank mechanism 12 in further detail and referring to FIGS. 2-5, it includes an angularly balanced crankshaft of conventional type indicated generally by the reference numeral 42 and journalled on the frame of the cutting apparatus 24 for rotation about its shaft axis. The crankshaft 42 has first, second and third cranks indicated at 44, 46 and 48, respectively. The first crank 44 is located on the crankshaft 42 intermediate the second and third cranks 46 and 48, has a throw equal to the throw of the second and third cranks, and is diametrically opposed to the latter cranks or angularly offset 180 degrees relative thereto. A first connecting rod 50 connected at one end to the first crank 44 is connected at its opposite end to the connecting member 28 by a yoke and pin connection, as best shown in FIGS. 1 and 3. 
     In accordance with the present invention a means is provided for dynamically balancing the first connecting rod 50, the connecting member 28 and the blade 24 as the crankshaft 42 rotates about its shaft axis to drive the reciprocally movable blade 26 in cutting engagement with a lay-up such as the lay-up 16. More specifically, the balanced crank mechanism 12 includes a second connecting rod 52 connected at one end to the second crank 46 and a third connecting rod 54 connected at one end to the third crank 48. A connecting rod pin 56 connected to the other end of the second connecting rod 52 and to the other end of the third connecting rod 54 extends therebetween. A pair of substantially identical balance weights 58,58 which together comprise a passive load are received on and carried by the connecting rod pin 56. The centers of gravity of the two balance weights 58,58 which comprise the passive load are located along the axis of the axis of the connecting rod pin 56 which is parallel to the axis of the crankshaft 42. The passive load is supported by the second and third connecting rods 52 and 54 and by a link 60 pivotally connected at one end to the connecting rod pin 56 and supported at its opposite end by a pivotal connection for movement about a pivot axis 62 spaced from and fixed relative to the shaft axis. The connecting rods 52 and 54 and the link cooperate to support the passive load to reciprocate along another path which, as shown, is arcuate and to move in directions generally opposite the directions of movement of the blade in response to rotation of the crankshaft 42 about its shaft axis. The opposition ends of the arcuate path of the passive are located generally along a rectilinear extension of the rectilinear path of the cutting blade 26.