IMPROVED BLADE SHARPENING AND GUIDE MECHANISM

Abstract: Blade sharpening device for numerically controlled cutting machines for cutting sheet-like materials like fabrics, plastics etc., having a cutting head which moves over the surface of a cutting table by two carriages with orthogonal movements. During the sharpening process the reciprocating blade of the cutting head is raised above the cutting sur­ face and the cut material. A motor for the drive of sharpen­ ing grinders and a numerically controlled clutch connecting the motor shaft with the grindstone shaft are mounted to the cutting head. The grinders are part of a V-shaped mount assembly - one grinder at each arm - pivotally mounted around the grindstone shaft which has a friction wheel at its top end on which the drive motor can act by a further friction wheel which is part of the clutch; see Figure 3.

Description: BACKGROUND The invention relates to a blade sharpener for a laminar material cutting apparatus as specified in the preamble of claim 1. A cutting apparatus of this art is known by FR-A-2 473 384. Said cutting apparatus as part of a numerically controlled cutting machine for cutting sheet material such as fabrics, plastic, etc. may be utilized to cut multiple lay-ups of said sheet material. The vertically arranged shaft is in driving connection with the orientation drive motor by planet-gear means and includes coupling and brake means for disconnecting the blade from and connecting said shaft with said sharpening wheels and vice versa. Because of the excentric mounting of the yoke on said shaft centrifugal force causes the one or the other set of sharpening wheels to be biased into sharpening engagement with an associated side of the blade supported for vertical reciprocation during driving in the one or other sense, when said coupling and brake means are energized. The use of a planet gear connection for transferring the driving force to the blade or to the shaft is expensive and complicates the service of the apparatus. Due to the fact that both the bias force for the grinding action and the torque for turning the blade must be generated by the orientation drive motor, the planet gear connection between drive motor, blade and shaft is subjected to a great wear and abrasion. The present invention is concerned with the improvement and simplification of apparatus for sharpening the blade of a cutting head of a numerically controlled cutting machine. In accordance with the invention an improved apparatus for sharpening the cutting blade of a cutting machine is provided. The improved blade sharpener comprises a friction wheel at one end of the drive shaft to which a clutch mechanism is associated which includes a lever pivotally mounted with one end to the frame of the cutting head, an actuator in linkage connection with the other end of the lever and bearing a rotatable friction wheel, and a reversible sharpening motor fitted to said frame; the actuator at command closes the kinematic chain between drive shaft and sharpening motor by friction wheels, so that depending on direction of rotation of the motor the V-shaped mount is inclined around drive shaft until one of the sharpening wheels comes in contact with the blade. The use of a separate reversible motor for driving the sharpening wheel via a pivotably mounted friction gear acting as a clutch leads to a very effective and simple wear resistent sharpening device which is in engagement only during transmission of motion to the sharpening wheels. During the cutting procedure, the blade is guided around said Z-axis which is perpendicular to the surface of the table, by a separate orientation drive motor which is controlled by the numerical unit referred to above. In this way, the blade is constantly held tangentially to the path described on the X-Y-plane without any mechanical connections to the sharpener. DESCRIPTION OF THE DRAWINGS Figure 1 is a general diagrammatic view of the machine where the cutting process is carried out, Figure 2 is a diagram showing the execution of the X-Y movement Figure 3 is a general diagrammatic view of the cutting head. Figure 4 is a ground plan, showing the most important components involved in this invention, in the clutched position for sharpening. Figure 5 is a ground plan of the same mechanism, but with the clutch released. DESCRIPTION OF THE SOLUTION The following is a description of the solution proposed in this invention, with reference to the attached drawings. Figure 1 is a diagrammatic overall view 20 of the automatic machine to cut fabric of the type normally used and on which the solution in this invention can be applied. It shows the material to be cut 24, placed on the penetrable cutting surface 26. The X-Y movement assembly, 14, moves over the cutting area, 60; the Y axis carriage, 62, carries the cutting head, 81 in fig. 3, which has the two aforementioned movements and, in addition, which can orient the blade, 106 in fig. 3, at a tangent to the path, 83, described on the X- Y plane. Assembly 81 incorporates the sharpening mechanism which is the object of this invention. By way of illustration, a description is given of the X-Y movement unit. As is shown in detail in fig. 2, this assembly is made up of an X carriage, 49, and a Y carriage, 62. The former is located at right angles to the guides, 64, so that the Y carriage, which moves on guides fitted on the X carriage, moves at right angles to the said X carriage. Both axes move according to the same principle, so that only the X axis is described. The motor, 66, is located at one end of the cutting area and a unit is made up by it, the tachometer, 68 and the position transducer, 70; this assembly forms part of a position servo. The motor, which makes use of a reduction - 72-74 - drives shaft 76 which runs across the cutting table from one side to the other. At each end of the shaft are the geared pulleys, 78 and 80, around which the belts, 82 and 84, run, under tension from the tensing pulleys 86 and 88. Carriage 49 is driven by belts 82 and 84, to which it is attached. The Y motor, 90, is fitted on the X carriage, 49, with the tachometer, 92, the position transducer, 94, gears 96 and 98, the conductor pulley 100, pulley 102 and tensor pulley 104 for driving the Y carriage, 62. The command signal for the X and Y position loops comes from controller 18. The cutting tool, 106 in fig. 3, has a cutting edge which is parallel to the Z axis, 117, itself at right angles to the cutting surface, 26; the tool, 106, is guided around the Z axis by means of a motor, 60. At time intervals commanded from the controller, 18, which may be variable according to certain parameters of the material to be cut (height, strength, etc.), the blade must be sharpened and it is here that the basic reason for this invention is to be found. The cutting head 81 in Figures 3, 4 and 5 carries the mechanlsms for the orientation of the blade: this includes the motor 60, the corresponding pulleys 63-63' and belts 64-64' which orient the fabric pressure base 79, in which the blade is fitted 106. This blade has a reciprocating up and down movement generated by the eccentric 74 which receives this movement from another motor (not included in the plan) through belt 76. Also fitted is the sharpening mechanism which includes a V-shaped mount assembly 110 pivotally mounted around a drive shaft 114; to which are rotatably fitted two sharpening grinders 112-112', one an each arm. For their part, these grinders receive their sharpening movement from the drive shaft 114, thanks to continuous belt 116; drive shaft 114 has a friction wheel 115 at its top end. This whole assembly 110 may be oriented around the Z-axis 117 at right angles to the cutting surface, as has already been mentioned. In turn, in the head 81, but in fixed positions on the frame, a sharpening motor 118 and a clutch 120 are fitted; this clutch is made up of an actuator 122 in linkage connection with a lever 124 which is pivotally mounted on a shaft 126, fixed in the frame of the cutting head, and of a friction wheel 128 which is rotatably supported at the other end of the lever 124. The operation of the mechanism is now described: During cutting time, the clutch mechanism 120 remains in the position which is shown in Figure 5, so that the fabric press base 79 including all its mechanisms, with respect to the frame can rotate freely, driven by the servomotor 60 and its transmission, round axis 117. During this time the sharpening motor 118 is stopped. During the working process the cutting tool can be inserted in and removed from the material to be cut along the Z-axis by means of the cylinder 77 which shifts the moving part 75 of the vertical movement assembly 73 (Figure 3). When a sharpening cycle is required controller 18 sends an order which sets the following sequence in movement: Cylinder 77 raises the blade to the point where it is not in contact with the fabric; servomotor 60 turns the fabric press base 79 to the preset position indicated in Figure 4; actuator 122 operates, closing the kinematic chain between shaft 114 which drives the grinders 112-112' and sharpening motor 118 by means of the friction wheel 128; finally, motor 118 comes on. As a result, the V-shaped mount 110 is inclined under the action of the belt tensions in one direction acound drive shaft 114 until it comes into contact with blade 106. After a number of turns in one direction sharpening motor 118 changes the driving direction and the V-mount 110 turns the other way round drive shaft 114 until the other grinder 112' comes into contact with the other side of the blade 106 for further sharpening. When this whole process is completed the sequence is executed in the opposite direction, with the blade returning to its earlier alignment and the cutting process is resumed. In order to prevent potential problems arising from the interruption of a continuous cut and its resumption (possible fabric shift), the controller has stored in the memory not only a minimum cutting distance between one sharpening operation and another, but also a percentage allowance which allows it to decide the sharpening order at the sharp angle prior to or following the theoretical sharpening point. By "sharp angle" it is understand an angle at which the blade turns while the X-Y motors are off, i.e. there is a sudden change in the tangent slope to the path: during the cutting of a consistently varying curve on the slope, the movements of the three motors X, Y and Z are simultaneous.

Claims: A blade sharpener for a laminar material cutting apparatus (81) with a cutting blade (106) having a cutting edge and a blade support (79) and being rotated by an orientation drive motor (60) about a Z-axis (117) perpendicular to a work supporting planar surface (61) to orient the blade (106) in a cutting operation in a selected cutting direction, a frame (62) for carrying the drive motor (60) and rotatably supporting the blade support (79), a moving device for positioning the frame (62) along an X-Y coordinate system, sharpening wheels (112) suspended from the blade support and adjacent the cutting edge (108) of the blade for rotation about a perpendicular axis with respect to the blade, a V-shaped mount (110) pivotally mounted around a drive shaft (114) which is mounted on the blade support (79) and parallel to the Z-axis (117), an endless belt (116) in driving connection with the sharpening wheels (112, 112') journaled on said mount (110), characterized in that the drive shaft (114) has a friction wheel (115) at one end to which a clutch mechanism (12) is associated which includes a lever (124) pivotally mounted with one end (126) to the frame of the cutting head (81), an actuator (122) in linkage connection with the other end of the lever (l24) and bearing a rotatable friction wheel (128), and a reversible sharpening motor (118) fitted to said frame; the actuator at command closes the kinematic chain between drive shaft (114) and sharpening motor (118) by friction wheels (115, 128), so that depending on direction of rotation of the motor (118) the V-shaped mount (110) is inclined around drive shaft (114) until one of the sharpening wheels (112, 112') comes in contact with the blade (106). A blade sharpener according to claim 1, characterized in that the drive shaft (114) is mounted on the blade support (79) of the cutting head (81) fitting the blade (106) and is rotatable with the blade, whereas the clutch mechanism (120) is in a fixed position at the frame (62) of the cutting head (81) and that, for sharpening, the blade is raised (cylinder 77) and turned (cutting blade orientation motor 60) into the sharpening position.

Inventors: CARRASCO, RODRIGO BECERRA, GALAN, MARIO ANDRADA, PEREZ, BERNARDO ALCANTARA, Pérez, Bernardo Alcantara
Applicants: INVESTRONICA S.A.
Application year: 1987
Main classification: B26D7
IPC codes: B24B3, B26D7