Patent GB-876328-A (GB)
Title: Improvements in or relating to knife sharpening machines
Inventor: ELLIOTT WILLIAM
IPC: B24B3/36
Filed: 1957-12-12
Abstract: 876,328. Sharpening knives. ELLIOTT, W., and ELLIOTTS LIVERPOOL Ltd. Nov. 25, 1958 [Dec. 12, 1957], No. 38581/57. Class 60. A machine for sharpening knives, particularly microtome knives, comprises a sharpening or honing plate (e.g. of glass) rotatably supported on a crankpin or eccentric and a knife holder or carrier for supporting a knife to be sharpened with an edge thereof in contact with the plate. A circular glass plate 11 rests on nylon studs 12 on the arms of a spider 13. The plate 11 is freely rotatable on the crankpin 19 of a crank 14 rotated through reduction gearing 15 and belt drives from an electric motor 18 located in the hollow base 10. The knife K to be sharpened is held by a detachable knife carrier 23 on the end of a bar 22 passing through a bearing 21 carried by a pillar 20. As sharpening proceeds the knife is turned at appropriate intervals to apply the opposite faces of its edge alternately to the plate 11. This may be done manually by turning a knob provided on the outer end of the bar 22. Mechanism for automatically turning the knife comprises a crank 24 secured on the bar 22 and coupled to a connecting rod 25 having a forked end 26 engaging with a crankpin 27 on a crank 28 mounted on a shaft 29 driven from an electric motor 30, located in the base 10, through gearing 29a, cranks 29b, 29c and a link 29d. A block 25a secured to the connecting rod 25 is bored to receive an adjusting screw 31 having a nut 32 and held against rotation by a retainer 33. A tension spring 34 is joined to the screw 31 and to the crankpin 27 so that the pressure of the knife on the plate can be adjusted. A rearwardly projecting pin 35 provided on the connecting rod 25 is adapted to pivot in a V-notch 36 in a pivot plate 37 mounted on the bracket 20. Alternatively, the pin 35 may be on the bracket 20 and the pivot plate 37 on the connecting rod 25. The motor 30 driving the crank 28 and its associated mechanism for turning the knife is controlled by a switch 38 operated by a cam 39 driven from the motor 30. The length of time that either facet of the knife edge rests on the plate is determined by the position of a selector switch 49 controlling the supply of current to the motor 30 through switches 40, 41, 42 actuated by cams 43, 44, 45 on a common shaft driven from the driving shaft of the plate 11 by pulleys 46, 47 and belt 48. The selector switch 49 gives the following possibilities, viz. (1) switch 42 in circuit, knife turned every 15-20 seconds, (2) switches 42, 41 in circuit, knife turned every 5-10 seconds, and (3) switches 42, 41, 40 in circuit, knife turned every 3-5 seconds. A solenoid brake 50 prevents over-running of the motor 30. At the beginning of sharpening, a fairly coarse grinding powder or paste is used ; as sharpening proceeds fine abrasive powders or pastes are used, the knife being finally stropped on a clean glass plate with only a little oil and turned over more frequently, the pressure of the knife on the plate being reduced. The spider 13 is mounted on an internally threaded nut 51 rotatable by a handle 53 on a screw threaded boss 52 on the base 10 so as to adjust the angle of sharpening.