US2759114A - Hair cutting machine having a vibrating armature drive - Google Patents

Description

Aug. 14, 1956 W. RoLLl ET AL 2,759,114

CHINE HAVING A VIBRATING ARMATURE DRIVE HAIR CUTTING MA l Filed July 22, 1952 /NVEN TOR S.

, HERBERT HAUSRATH KLEVT WENDE L RoLLl AND ERICH BY.'

United States Patent HAIR CUTTING MACHINE, HAVING A. VIBRATING ARMATURE DRIVE Wendel Rolli, Stuttgart-Degerloch, Herbert Hausrath, Karlsruhe, and Erich Klett, Stuttgart-Bad Canstatt, Germany, assignors to Robert Bosch G. m. b. H., Stuttgart, Germany Application July 22, 1952,I Serial No., 300,248 Claims priority, application Germany August 10, 1951 Claims. (Cl. 310-29) The present invention relates to a hair cutting machine having an electromagnetic drive including a vibrating armature which is periodically attracted by an electromagnet excited by alternating current.

Constructions of hair cutting machines are already known in which the armature of the drive magnet is fixed to a leaf spring or the like, is polarised by means of a permanent magnet, and swings to and fro between the pole shoes of an electromagnet. Despite a considerable power intake such arrangements are only capable of iniparting a small driving power to a cutter head. Theref ore it has already been attempted by Various ways and means to combine the oscillating parts of the cutter head with swinging armature systems whose natural frequency coincides with the exciter frequency of the electromagnet. But those measures were only satisfactory to. a small extent.

The present invention is based on the knowledge that in the known arrangements the electromagnetic tractive forces are. unfavourably related to the actual position of the oscillating armature, because the forces reach. their maximum value just at that time when the armature is closest to the electromagnet and the cutting blade 0f: the cutter head has reached one extremity of its traveh i. e. a point, on its track at which it reverses.v An arrange,- ment correspondingy to the kinetic principles would therefore have to produce oppostcly acting driving forces, especially at the aforedescribed moments, so that a phase displacement of 180," should exist between deflection and driving force.

This requirement has been fulfilled by the. fact that the. oscillating armature. in accordance with the invention rolls over a preferably slightly curved surface during its. working movements, whereby the. lengths of. the momcntary load and the effort lever arms of the armature vary constantly.

The. invention will be further described with reference to the accompanying Vdrawings which show hy way of example one embodiment of the invention- In the drawings.:

Fig. 1 is a longitudinal section, along the lino 1.*-1 of Fig. 2., of a hair cutting machine driven by a rocking armature,

Fig. Z is. another longitudinal section along the line lI-Il of Fig. l with the cutter head removed, and

Fig. 3 is a cross section along the line Ill-sill of Fig. l.

The driving mechanism of the hair cutting machine shown in the drawings is housed in two handle parts. 11 and 12 of pressed material and consists essentially of an E-shaped magnet core. 13, a laminated oscillating or rocking armature 14 and a cranked driving arm. 155 mounted on the armature. When a cutter headv 16. is attached the arm 1 5 engages in a recess ouv the cutter blade. Exciter coils 20, y21 arey slipped over outer arms 17 and 18 of the magnet core 13,. The exciter coils 20 and 21 which are wound with the same number of turns and are so 'disposed that on being connected to an alternating current supply in a circuit including a tumbler c ICC switch 22, they magnetise the free ends of they outer arms 17, 18 with opposite polarities.

The centre arm of the magnet core 13 includes a permanent magnet 2.4 having a pole piece 19 assembled from sheet iron. The various parts of the magnet core, that is to say the outer arms 17 and 1 8, the portion interconnecting them, the permanent magnet 24 and pole piece 19, are held together by two brass plates 28 and` 29,.

When the armature 1,4 is in its central position as shown in the drawings the permanent magnet 24' magnetises the two outer arms 17 and 18 symmetrically with a permanent magnetic flux as indicated by the broken arcuate arrowed lines in Fig'. 2. The alternating UX produced by the exciter coils 20 and l21 is supcImPOSed on this permanent flux. By the suitable choice of the number of turns in the exciter coils the amplitude of the alternating flux may he so adjusted that it is substantially or nearly equal to the magnitude of the. permanent flux. If therefore the magnetic flux in one outer arm, for example 17, owing to the current in exciter coil, for example 20, has just assumed double the value of the permanent flux, then the flux is substantially or nearly nil on the, other arm,I for example 1S, and the centre portion of the armature 1,4 rolls along the centre arm of thc magnet core which is adapted to form an arcuate rocking surface. 25', in the direction of the more extensively magnetised outer arm, for example 1,7. )n re,- versal or" the, current thrnugh the, exciter coils during the following half-cyclei the magnetic, llux in` the other outer arm, `for example 1S, reaches substantially or nearly double the value of the permanent ux so that the armature is forced to swing in the opposite. direction whereby its central portion rolls on the arcuate surface 25 in the opposite direction.

Arranged opposite the centre of the rocking surface are resilient pivoting means, i. e., a retaining spring `26, one end of which is inserted in a recess 27 in the casing wall 12 whilst its other end projects in to an oppositely extending bore in the armature 14 and thus secures the armature from longitudinal displacements. The spring 26 accordingly is a bearing element made of resilient material. It also serves the purpose of returningI the armature 14 to the centra-l position as shown, in the event ofl the current through the exciter coils current being interrupted.

As the armature rolls the force exerted by the spring 26 increases linearly andk the length of the lever arm of the armature on which the spring presses in a return direction also increases approximately linear. Thus the moment exerted by ther spring force, in the returning dirccti'on rises steeply and, in fact, approximately quadratically. The attractive force, exerted by the magnet system increases in accordance with the approach. of the armature to the magnet pole in question and. in fact also increases. quadratically. In the meantime as the armature rolls the length of the lever arm on which the magnetic f orce acts decreases approximately linearly, so that the torque produced by the magnetic force increases more gradually than the returning moment produced by the spring force.

In this cycle of movement of the armature the constant change of position of the instantaneous centre and the consequent change in length of load and effort arm of the armature plays an important part. As, the radius of curvature of the rolling surface 25 is considerable, it preferably amounts to, more than 20 times the: length of the rolling surface-the point of abutment ofthe, armature changes rapidly. Therefore a slight; approach of the armature to one of the outer arms, 17 for example, of the magnet core is sulicient to. roll thc armature from the centre M' of the arcuate rocking surface to for example the end A of this surface, whereby the length of the load arm decreases trom CM to CA, whilst on the other hand the length of the effort arm is reduced from BM to BA. In the embodiment shown, CM=65 mm., CA=40 mm., Bit/1:32 rnm. and BA=10 mm. The ratio k of the lengths of the load and effort arms thus changes for the left half of the armature from As may be easily seen, the length of the lever arm upon which the spring1 26 presses when the armature is attracted from the central position, is initially practically zero, but increases rapidly to AM. ln this manner the amature does not strike the outer pole piece if the spring 26 has been suitably chosen, and yet despite this ensures a strong driving impulse for the cutter blade up to shortly before reaching its reversing point.

In a further development of the invention it is naturally possible in such an arrangement to tune the spring pressure and the mass of the swinging parts to the frequency of the electric supply to the exciter coils. This may be achieved by so arranging the spring that it may be adjustably pre-compressed.

We claim:

1. An electro-magnetic drive for driving a cutter head in a hair cutting machine, including an electro-magnetic system having a core member, an armature member and exciter coils, said core member being E-shaped and having two outer arms and one centre arm, said centre arm having an arcuate outer surface, resilient pivoting means, pivotally holding said armature in abutting contact with said arcuate surface of said centre arm while permitting displacement of the armature from a given position towards either of said outer arms, said exciter coils being disposed on said outer arms for energisation of the electro-magnetic system from an alternating current electricity supply, and means to produce a permanent magnetic ux linkage at least said centre arm.

2. An electro-magnetic drive according to claim l, said exciter coils disposed on said outer arms being adapted to produce instantaneously oppositely acting magnetic fluxes in said outer arms whereby said outer arms are magnetised in opposite directions to one another.

3. An electro-magnetic drive according to claim l, a permanent magnet in said centre arrn for producing a permanent magnetic ux linking said core.

4. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the E-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passing through one of said openings in said casing; an elongated armature having a substantially central portion thereof located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core member so as to define a path with said E-shaped core member for the magnetic flux produced by the coil windings when energized; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E-shaped core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

5. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casg. ing with the arms of the E-snaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface and being longer than the outer arms of said E-shaped core member; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passing through one of said openings in said casing; an elongated armature having a substantially central portion thereof located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core member so as to define a path with said E-shaped core member for the magnetic ux produced by the coil windings when energized; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E-shaped core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

6. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the i-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface whose radius of curvature is equal to substantially ten times the peripheral length of said arcuate surface; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passing through one of said openings in said casing; an elongated armature having a substantially central portion thereof located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core member so as to define a path with said E-shaped core member for the magnetic ux produced by the coil windings when energized; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E-shaped core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

7. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the E-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface and being longer than the outer arms of said E-shaped core member, said arcuate end surface having a radius of curvature equal to substantially ten times the peripheral length of said arcuate surface; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passing through one of said openings in said casing; an elongated armature having a substantially central portion thereof located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core member so as to define a path with said E-shaped core member for the magnetic flux produced by the coil windings when energized; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface` in accordance with the energization of the coil windings, the maximum travel of said armature towards said cuter arms of said Efshaped` core member being limited by said free arcuate. end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

8. Iny a hair clipper, in combination, an elongated cas ing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the Eshaped core member exa tending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member; a pair of energizing conductors passing through one of said openings in said casing and connected tothe coil windings, said coil windings when energized producing oppositely acting magnetic iiuxes in said outer arms of said E-shaped core member so as to magnetize said outer arms in opposite sense with respect to one another; an elongated armature having a substantially central pore tion located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core meme ber so as to deline a path with said E-shaped core mem-4 ber for the magnetic flux produced by said coil windings; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock, on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of Said armature towards said outer arms of said E-shaped Core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

9. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with, an opening; an E-shaped core member supported in said casing with the arms of the E-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface, a portion of said center arm being partially in the form of a permanent magnet; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passing through one of said openings in said casing; an elongated armature having a substantially central portion thereof located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core member so as to deine a path with said E-shaped core member for the magnetic iiux produced by the coil windings when energized; resilent means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E-shaped core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

10. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the E-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface, a portion of said center ann being partially in the form of a permanent magnet; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member; a pair of energizing conductors passing through one ofsaid open-ings said casing and connected to the coil windings, said coil windings when energized produce opposite acting' magnatiel fluxes in said outer arms of said E-shaped core member so as to magnetize said outer arms in opposite sense With respect to one another, the density of the magnetic ux produced by said coils being substantially equal to the density of the magnetic flux produced by said permanent magnet; an elongated armature having a substantially central portion located against said arcu-l ate surface, and having opposite end portions respecs tively located opposite the free ends of said outer arms of Said E-Shped core member so as to define a path with said E-shaped core member for the magnetic flux produced by said coil windings; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings; and transmis,- sion means connected to said armature for movement therewith., extending through said other opening.

il. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the E-shaped core member ex tending transversely to the lengthof said casing, the center arm of; said E-shaped core member having a free arcuate end surface and being longer than the outer arms of said Efshaped core member, a portion of said center arm being partially in the form of a permanent magnet; a. pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passingthreugli one. ot said openings in. Said. Casing; an elongated armature having a substantially central portion thereof located against said arcuate surface, and having opposite end portions respectively located opposite the free. ends of said outer arms of said E-shaped core mem. ber so as to define a path with said Eeshaped core mem= ber for the magnetic flux produced by the coil windings when energized; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E- shaped core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

lZ. In a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an le-shaped core member supported in said casing with the arms of the E-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free arcuate end surface, a portion of said center' arm being partially in the form of a permanent magnet, said center arm being longer than the outer arms of said E-shaped core member; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member; a pair of energizing conductors passing through one of said openings in said casing and connected to the coil windings, said coil windings when energized produce opposite acting magnetic fluxes in said outer arms of said E-shaped core member so as to magnetize said outer arms in opposite sense with respect to one another, the density of the magnetic flux produced by said coils being substantially equal to the density of the magnetic flux produced by said permanent magnet; an elongated armature having a substantially central portion located against said arcuate surface, and having opposite end portions respectively located opposite the free ends of said outer arms of said E-shaped core member so as to define a path with said E-shaped core member for the magnetic iiux produced by said coil windings; resilient means engaging said armature for urging the same into abutment with said arcuate surface of said center arm so as to cause said armature to rock on said arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E-shaped core member being limited by said free arcuate end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

13. in a hair clipper, in combination, an elongated casing having opposite ends each of which is formed with an opening; an E-shaped core member supported in said casing with the arms of the E-shaped core member extending transversely to the length of said casing, the center arm of said E-shaped core member having a free end surface; a pair of coil windings arranged respectively about the outer arms of said E-shaped core member and adapted to be connected to a pair of energizing conductors passing through one of said openings in said casing; an elongated armature having a substantially central surface thereof located against said free end surface of said E-shaped core member, one of said surfaces being arcuate, said armature having opposite end portions respectively located opposite the free end portions of said cuter arms of said E-shaped core member so as to define a path with said E-shaped core member for the magnetic flux produced by the coil windings When energized; resilient means engaging said armature for urging the same into abutment with the free end surface of said center arm so as to cause said armature to rock on the arcuate surface in accordance with the energization of the coil windings, the maximum travel of said armature towards said outer arms of said E-shaped core member being limited by said free end surface of said center arm; and transmission means connected to said armature for movement therewith, extending through said other opening.

14. An electromagnetic drive for driving a cutter head in a hair cutting machine, including an electromagnetic system having a core member, an armature member and exciter coils, said core member being E-shaped and having two outer arms and one center arm, a permanent magnet in said center arm for producing a permanent magnetic flux linking said core, said center arm having an arcuate outer surface, means to resiliently urge said armature into abutting contact with said arcuate surface of said center arm and to permit displacement of the armature from a given position towards either of said outer arms, said exciter coils being oppositely acting and being disposed on said outer arms for magnetizing said outer arms in opposite directions to one another, and means for exciting said exciter coils from an alternating current electricity supply whereby the magnitude of the excitation of the electromagnetic system from the exciter coils is approximately equal to the magnitude of the premagnetization produced by said permanent magnet.

15. In a hair cutting machine, in combination, a housing unit; an electromagnetic core unit arranged within said housing unit, one of said units having a guide face; an elongated armature having a portion with a face thereof superimposed on said guide face, at least one of Said faces being curved so that said elongated armature is adapted to carry out an oscillatory rolling movement on said guide face; and a bearing element consisting of resilient material and interposed between another face of said portion of said elongated armature and one of said units and supporting said portion of said elongated armature for damped movement in directions required during oscillatory rolling movement of said armature on said guide face.

References Cited in the le of this patent UNITED STATES PATENTS 1,891,486 Wahl Dec. 20, 1932 1,895,292 Miner Ian. 24, 1933 2,063,116 Nordhem Dec. 8, 1936 2,304,525 Andis Dec. 8, 1942 2,404,227 Hall July 16, 1946 2,610,995 Orsatti Sept. 16, 1952 FOREIGN PATENTS 187,234 Switzerland Jan. 16, 1937 436,717 Great Britain Oct. 17, 1935 887,698 France Aug. 16, 1943

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