Patent GB-375850-A (GB)
Title: Improvements in a machine for sharpening saws
IPC: B23D63/10
Filed: 1931-03-30
Abstract: 375,850. Sharpening saws &c. MOULIN, E. DU, 41, Avenue des Nerviens, and MAYENCE, M., 99, Square Josephine Charlotte, both in Brussels, Belgium. March 30, 1931, No. 9636. Convention date, March 29, 1930. [Class 83 (iii).] Reciprocating fling-machines.-In a machine for sharpening saws and the like, particularly band saws, the longitudinal feed of the saw and the setting in the direction of the height of the teeth are each effected as the result of two independent displacements in opposite directions one of which is dependent on the tooth spacing and the other independent thereof the resultant movement being generally in the direction of the independent displacement. It is desirable that the longitudinal feed of the saw be in the direction M<1>, Fig. 1, since otherwise the burr m<1> produced in sharpening a tooth is raised to the position m in operating on the next tooth. The independent displacement may be produced by feed rolls while the other displacement is effected by a pawl device which places the tooth to be sharpened exactly in the plane of the operative edge of the file. Thus in Figs. 3 a .. e, the file edge being located in the plane O-O<1>, the tooth 1 which has just been sharpened is first moved to the left by the rolls G through a distance E + x, E being the distance from the plane O-O<1> to the edge of a shield P coacting with the feed pawl K.and x being a small additional distance required to bring the sharpened tooth beyond the edge of the pawl shield. The pawl K is then actuated to engage in the next tooth 2 to be sharpened and to move this tooth through the distance R, Fig. 3d, into the sharpening plane, the feed rolls being separated to permit the pawl feed movement. The pawl is then withdrawn and at the end of its withdrawal movement it passes on to the shield P. In a modification, these movements may be effected in the reverse order. The method may also be applied to rectifying saws having unevenly spaced teeth. In this case after the feed to the left, Fig. 5d, produced by the rolls G, the pawl is arranged to engage with the tooth 1 which has just been sharpened and to move this tooth back to a distance e equal to the average tooth spacing, from the sharpening plane 0,01 ready for the operation on tooth 2. The usual backing-up guide for the saw is dispensed with and the point of the feed pawl acts as a height setting device and ensures that all the sharpened teeth are of the same height. For this purpose the saw is moved in the direction of the height of the teeth during the feed and is brought back to correct position by the pawl K. This movement may be effected by various means such as by inclining the feed rolls G, Fig. 6a, or by using a spring member T engaging the back of the saw. The extent of the backward movement in the direction of the arrow R produced by the pawl may be limited by a guide H on which the pawl rides during the subsequent longitudinal movement. The file L, Fig. 8, is carried eccentrically in holders P so that the operative edge A coincides with the axis of adjustment of the holder and the setting for different tooth angles does not disturb the position of the operative filing edge. In Fig. 15 the file holders are integral with a member 2 and a central clamping screw 81 is employed. In order to ensure even pressure of the file without the use of a back support, the file L is rigidly connected by an arm E, Figs. 9a, 9b, to a pivotal axis O,O<1> connected to an axis B on or round which a member A may pivot. During the stroke of the file the member A engages a projection C and tilts the file about the axis O,O<1> in the direction of the arrow F to keep the file in firm engagement with the work, the pressure between the tool and the work being automatically limited to that permitted by the pressure of the workclamping jaws. In order to distribute the points of maximum clamping pressure along the saw and prevent tilting of the saw under the pressure of the tool the movable clamping lever L carries a clamping jaw provided with a number of compression centres O,O<1> and consisting of relatively movable parts A, B, C connected. together by springy portions arranged round the centres O,O<1>. The saw is gripped between the members C, E and the tooth being sharpened is located betwteen the points O, O<1>. A machine for carrying out the method described above consists of a frame 1 having an upper part E forming the fixed jaw of the clamp for a band saw 5 which passes over a pulley carried by an adjustable bar. The pulley 26 driven from a countershaft 28 drives through a hand-controlled clutch 29 a shaft 38 carrying a crank disc 4 which reciprocates a shaft 33 connected to the file holder 2. The feed movement of the saw independent of the tooth spacing (corresponding to that produced by the rolls G) is effected by means of toothed segments 16, 17 which have circular portions engaging the saw, the segment 16 being rocked to effect the feed by means of a cam 18 and lever 22. The circular portions are inclined so that when the saw is moved longitudinally it is also raised out of its clamp. During the pawl feed and the return of the segments, the segment 17 is withdrawn by means of a cam 19 and lever mechanism 14, 15. The feed pawl 23 is held in engagement with the saw teeth by a spring and has a guide finger sliding on a shield 44. When the pawl guide finger leaves this shield it passes on to an adjustable member 42 which determines the position of the tooth gullet during operation. The pawl is reciprocated by a lever 13 operated bv a cam 20, and the movable clamping jaw of the saw is operated through lever mechanism 8 from a cam 21. The pivotal movement of the file carrier is effected by a member 35 (corresponding to the member A in Fig. 9) which is adjustably pivoted at 69 to the shaft 33.