Patent GB-1456024-A (GB)
Title: Method of and apparatus for cutting sheet material
IPC: B23D47/04
Filed: 1973-11-21
Abstract: 1456024 Circular saws J H EDWARDS 21 Nov 1973 53955/73 Heading B5L A method of cutting sheet material supported on a table by a circular saw blade movable along a slot in the table comprises initiating a cycle of operation of the apparatus containing the blade in order to permit the blade to make a cutting traverse from a starting location along the length of the table, moving the blade lengthwise of the table until the sheet material has been cut, and lowering the blade from its cutting position to a non-cutting position for the return traverse of the blade back to the starting location, the lowering being initiated as soon as a sensor has detected that there is no sheet material adjacent to the blade. Apparatus for performing the method comprises a table 10, Fig. 3, with a slot 12, and a saw blade 27, Fig. 1 within the slot and mounted on a carriage movable along rails 16, 17, Fig. 3. The carriage also supports a drive motor 25 for the saw blade and a gear box having an output shaft 40. A further shaft 43 is mounted for movement about the shaft 40 by a link 46 and is driven from the shaft 40 via gears 41, 42. The shaft 43 carries pinions 44, 45 engageable with racks 15, 14 respectively. The carriage also carries a sensor 50, Fig. 10, a pivoted support for the saw blade shaft, a lever 125 for holding the pivotal support raised, and a detent 56 controlled from a solenoid 53.  In operation of the apparatus a sheet to be cut is placed on the surface 101, Fig. 1, of the table and a clamp/guard 90 is lowered so that a pin 110 thereon is held in a hole in a spring- loaded pivoted plate 112, Fig. 8. A control 132, Fig. 1, is then operate manually to cause a hook 81 to be raised and allow the shaft 43 to move about the shaft 40 until the pinion 45 engages the rack 14. Further movement of the shaft 43 is prevented by a plate 60 thereon engaging a roller 59 of the detent 56, Fig. 10. The carriage is thus advanced causing the saw to cut the sheet material. The sensor 50 is first held down by a plate on the table and then by the sheet material until the edge of the latter is reached after cutting. The sensor then lifts to actuate a microswitch 51 which actuates the solenoid 53 to raise the detent 56 and roller 59 so that the plate 60 and pinion 44 are allowed to swing about the shaft 40. The pinion 44 first engages a tooth 127 on the lever 125 to swing the latter to a position in which it allows the sawblade support to drop and thus lower the sawblade below the surface of the table 10. This also causes a pulley 120 on the sawblade support to operate a cable 118 which pulls the plate 112 to relase the clamp/ guard and allow it to rise. The pinion 44 then swings farther to engage the rack 15 and consequently produce the return travel of the saw carriage. At the end of the return stroke the pinion 44 leaves the rack 15 and engages a non-circular member 66, Fig. 7, to rotate the same. Via linkage this causes a roller 74, Fig. 1, to rise to lift the sawblade support to its original position where it is held by the lever 125 returned by a spring. The shaft 43 with the pinion 44 then rotates to its initial position where it is held again by the hook 81. Where the sheet material is so large as to prohibit raising of the sensor 50 the detent 56 is operated when a sloping surface 141 thereon engages a bracket 140 on the apparatus frame. Should the saw blade stick in the material the detent 56 moves against the action of a spring 152 so that a projection 150 thereon actuates a microswitch 151 which actuates the solenoid 53 to release the detent.