Patent GB-689091-A (GB)
Title: Improvements relating to machines for sharpening saws or sharpening and setting saws
IPC: B23D63/00
Filed: 1949-06-03
Abstract: 689,091. Reciprocatory filing. CAMPBELL, E., and CAMPBELL, J. L., [Representatives of CAMPBELL, D.]. Jan. 28, 1952 [June 3, 1949], No. 14933/49. Class 83 (iii). A saw-sharpening machine which may also set the teeth, comprises a holder 53, Fig. 1, for the saw S, a frame 4 pivoted horizontally and having a guide-bar 8 pivoted vertically, a file carrier 53 reciprocated along the bar 8 by a rotary drive, and mechanism associated with said drive to pivot the bar 8 upwardly and the frame horizontally during the return stroke of the carrier 53 so that a file 11 supported by the carrier is raised clear of the saw S during its return strokes and during its forward strokes acts alternately at different obliquities to provide the two bevels required in saw sharpening. The file 11 is reciprocated along the bar 8 by a connecting rod 20 having universal joints 20A and driven by a cam 19 operating as a crank-disc. An electric motor 12 rotates the cam 19 through a chain-andsprocket drive 13, 14, pinions 16, 17 and a shaft 18. The cam 19 also raises the file 11 after the forward filing stroke by displacing a followerroller 22 mounted on an arm 21 projecting from the bar 8 so that the bar is rocked about its pivot 7 on the frame 4. A further roller 47, mounted above the roller 22, rocks a lever 42 mounted in a bracket 39 on the frame 4 when it is displaced with the roller 22 and so disengages a spring-pressed plunger 44 from one of the holes 48A in an arcuate rim 48 on the casing 1, 3 of the machine. The frame 4 is then swung horizontally about a pin 5 carried by a part 6 of the casing and having its axis coincident with the medial plane of the saw. As the frame 4 is swung between the positions C, D, Fig. 2, the saw is advanced by an amount equivalent to one tooth. The filing action is such that during each forward stroke of the file, which is of triangular section, the opposite faces of adjacent teeth are sharpened, the filing angle being changed during each advance of the saw. The horizontal swinging movement of the frame is controlled by a cam 27 which is rotated from the shaft 18 by pinions 28, 29, and mounted adjustably on the frame 4 by a bracket 23. A spring- pressed lever 35, Fig. 2, pivoted at 36 on the part 6 acts on the frame 4 to keep the cam 26 in engagement with an adjustable stop 49 on the rim 48 or with a finger 33 which is secured to the part 6 and can be adjusted by a screw 32 cooperating with a sliding block 31 carrying the finger. The saw-carrier 53, which includes a rigid jaw 54 and a jaw 55 operable by cam levers 56 to clamp the saw, is supported for movement in a dove-tail guide, Fig. 1, on the casing 1. The carrier 53 is advanced intermittently by a pawl 66 engaging the teeth of the saw and pivoted on an arm 72 fixed to a rod 68, the angle of the pawl relatively to the arm being adjustable by a screw 75. A further arm, 70, fixed to the rod 68, which is supported in bearings 69 on the part 1, is connected by a screw 71 to a lever 67 urged by a spring into engagement with a lever 64 pivoted at 65 to the casing. The lever 64 is rocked by a cam 62 driven from the motor 12 through pinions 60, 61 to advance the pawl 66, movement of the saw during the return movement of the pawl 66 being prevented by a further pawl (not shown), in engagement with the saw. A nut 52 on a screwed rod 50 pivoted on the bar 8 may be adjusted to vary the filing angle of the file 11. Adjacent teeth are set in opposite directions by a pair of opposed setting- devices arranged to operate on the teeth after they have been sharpened. Each of these devices, Fig. 3, comprises a jaw 78 fixed to the casing 1 and having a setting edge 78A, and a jaw 77 pivoted at 80 to the jaw 78 and having a setting edge 77A. The jaw 77 is influenced by a spring 83 to follow a cam 85 with a ratchetwheel 86 which rotates the cam under the control of a pawl 87 pivoted on a lever 88. The latter is rocked against the action of a spring 94 by cable 89 to allow the jaws to snap closed and set the tooth. A bell-crank 90, Fig. 2, operated by a lever 91 having a follower 93 in engagement with the cam 62, actuates a cable 89 for each device. The operation of setting a pair of adjacent teeth simultaneously is effected after alternate advances of the saw.