Patent GB-719840-A (GB)
Title: Improvements in or relating to dry shavers
IPC: H02K25/00
Filed: 1952-07-21
Abstract: 719,840. Dry shavers. KOBLER, V., and KOBLER, W., [trading as KOBLER & CO.]. July 21, 1952 [July 21, 1951], No. 18396/52. Class 131 [Also in Group XXXV] A dry shaver comprises at least one shearing head mounted on a casing forming a handle and having a movable cutter driven by an electric driving unit enclosed in the casing, and means, operable from outside the casing, for varying the speed of the cutter within a range from approaching zero up to a maximum value. As shown, a three-pole laminated armature 7 is journalled by a triangular-section shaft 6 between shields 4, 5 of insulating material secured by screws 3 over pole shoes of a magnet cone 2. An interrupter lever 8 is rigidly fastened to the shield 4 and a second interrupter lever is spring-pressed against the end of the shaft 6 and is reciprocated when the shaft rotates to close and open the contacts secured on the levers 8. Swing levers 12 engaging the cutters 13 are journalled on a shaft 11 carried by the shields 4, 5 and are eccentrically pivoted at 16, 19 in coaxial friction discs 15, 17 the disc 15 being carried by the shaft 6 and the disc 17 being freely rotatable on a projection 18 from the casing 1. The discs 15, 17 bear against a transmission disc 20 which is freely rotatable in a slide 21 adjustable along an arm 22 by a screw 23. The operating speed of the cutter on the lefthand side of the drawing depends on the rate of rotation of the shaft 6 but that of the other cutter can be slowed down to allow closer shaving by decreasing the radial distance of the point of contact of the disc 17 from the centre of the disc 20. In a modification the speed of some or all of the movable cutters of a multiple-head dry shaver is reduced by an adjustable screw on one of a pair of spring-urged interrupter levers co-acting with a flattened pin, rotated by a lever projecting out of the casing, to reduce the contact periods. In a further modification in which the adjusting screw controls the highest obtainable speed of the cutter the screw coacts with a rigid abutment block and the interrupter lever is adjusted by a slide movable along the lever. Further methods of altering the speed of the cutter include an electric switch arrangement by which the magnet winding may be tapped at different points, braking means to reduce the speed of the motor, arranging the armature to be axiallv movable in the magnet field, introducing a reduction drive between the cutter and the driving unit and the introduction of electric resistances which may be switched into the current circuit as desired. The shortening of the contact period allows the use of the same winding for a wider range of applied voltages since the heating of the coil is reduced. edge portion which is ground to form a cutting edge part 5 with, in the case of one blade of each pair, an oblique surface 6 sloping downwards from the cutting edge to ensure that contact between the blades at any time during a cutting action is restricted to a single point. Each blank has, also, a projecting portion which may be utilized to locate the blade while the cutting portion is tempered and is later machined by an end milling cutter guided by a pivot in the pivot pin bore 7, or by surface grinding, to provide pivotmounting sections 8, each section of a pair being the mirror image of the other and having a highest point Y and a lowest point X when the blade is placed in a horizontal plane with the pivot-mounting section uppermost. As the scissors are closed the highest points Y come together causing separation of the cutting edges except at the effective cutting point. A spring disc 12, Fig. 23, between the head of the pivot pin 11 and the outer side of one blade urges the blades towards each other and to avoid the use of a tempered pivot pin a tempered sleeve 13 is inserted in the bore 7 and screwed into a washer 15, held therein by a pin 14 and secured by a nut 16.