Patent GB-527787-A (GB)
Title: Improvements in or relating to cloth-cutting machines
IPC: B24B3/36
Filed: 1939-04-15
Abstract: 527,787. Sharpening cloth-cutters. MAIMIN CO., Inc., H. April 15, 1939, No. 11538. Convention date, April 16, 1938. [Class 60] Sharpening-means for the reciprocating knife of a cloth-cutting means are arranged to swing around the presser-foot guard into engagement with the knife, and to swing beyond the presserfoot guard at the end of the sharpening operation. The arrangement prevents the sharpening means, when not in use, from obstructing the operator's view, and moreover does not impair the cutting capacity of the machine. The machine shown in Fig. 1 comprises a reciprocating knife 5 mounted in a standard 2 and operated by a crank 8 driven by a motor 3. A slide 17, mounted in a guide-frame 15, carries a plate 18 supporting two spindles 19, Fig. 8, provided with plates 20 which support studs 21 carrying a double stone 22 and a single stone 23. A non-grinding element may replace the upper stone 22. The stones are driven in opposite directions through gears 29, 31, 31 operated by a shaft 28 which is journalled in the slide 17 and passes through a bevel-gear mounted in the frame 15 and geared to a driving-pinion 40, Fig. 4, which is mounted on a rock-arm 41 and is provided with a friction-wheel 43 adapted on operation of a trigger 54 to engage a wheel 9 driven by the motor. The slide 17 is reciprocated by means of a chain 46 which is geared to the pinion 40 and is provided with a roller 47 co-operating with a slotted block 48 on the slide. Normally, the stones are above the top of the knife and are in juxtaposition in front of the knife-guard 13. Stationary nuts 25 co-operate with threads 26 on the spindles 19 to swing the stones towards and away from the knife during descent and ascent of the slide. The rock-arm 41 is connected by a toggle-link 60 to an arm 58 which is connected to an arm 57 on the shaft 55 of the trigger 54. A latch 62 on the trigger normally abuts on a stop 63 on the slide 17. On release of the latch and movement of the trigger, a spring 59 rocks the arms 58,41, and the wheels 43, 9 engage. Thereupon the stones are rotated, the slide descends and the stones swing rearwardly into engagement with the knife, engagement being maintained by springs 24. During further descent, the stones traverse the knife, and at the bottom of the traverse the lower stone 22 passes the end of the knife, the upper stone remaining in engagement to prevent the lower stone from burring the knife when the stones ascend. On ascent of the slide, the stones are swung into normal position and, at the end of the cycle, the stop 63 co-operates with the latch 62 and the sheel 43 is disengaged. A brake-shoe 65 prevents over-running To prevent operation of the grinding-mechanism unless the presserfoot 12 has been lowered on to the base 1, the guard 13 is arranged when in raised position to obstruct a lug 67 on the arm 41. In the machine shown in Fig. 10, a slide 73 supporting stones 77 and a motor 89 is mounted in a guide-frame 71 which is pivoted at 70. Normally, the guideframe is held in inclined position, with the stones in front of the knife-guard 13, by means of a forked arm 115 which is pivoted to the housing 3 and engages a roller 119 carried by a rod 84 on the slide. The stones are mounted on pivoted arms 76 connected to links 80 having shoulders abutting on a bell-crank 83 which is carried by the rod 84 and has a roller 86 normally engaging the frame 71 and holding apart the stones. The motor 89 drives the stones through gearing 95 ... 98. The slide is traversed by means of a chain 103 which passes around sprockets on the slide and is connected by a link 104 to a pin 105 on the frame 71. The motor drives the bottom sprocket through gearing 107 ... 112. On depression of a switch 91, the motor is started, the stones rotate, the slide descends, the arm 115 is depressed, and a spring 120 moves the frame into the vertical position. The roller 86 rides down the frame and an incline 121 thereon, and permits a spring connecting the arms 76 to swing the stones rearwardly into engagement with the knife. During reciprocation of the slide, the stones are traversed along the knife, and towards the end of the return movement of the slide, the frame is restored to the inclined position, the stones are swung forwards, and a lug on the chain 103 opens the switch. A link 126 connected to the switch has a projection 128 which co-operates with the knife-guard to stop the grinding- mechanism if the presser-foot is left in raised position. The presser-foot may be telescopically mounted so that if left in raised position it is depressed by the stone-mounting and damage is prevented.