US3047948A - Drive finger for vibrating motor - Google Patents

Description

Aug 7, 1962 J. F. WAHL 3,047,948

*1" DRIVE FINGER FOR VIBRATING MOTOR Filed April 8, 1959 INV EN TOR.

JbhlzF Wahl BY Wm W6 United States Patent 3,047,948 DRIVE FINGER FOR VIBRATING MOTOR John F. Wahl, Sterling, Ill., assignor to Wahl Clipper Corporation, Sterling, III., a corporation of Illinois Filed Apr. 8, 1959, Ser. No. 804,940 3 Claims. (Cl. 30-210) This invention relates to a vibrating motor and more particularly to a drive finger for a vibrating motor used in electric hair cutters.

The present subject matter is disclosed but not claimed in my prior co-pending application for Electromagnetic Vibratory Unit, Serial No. 734,605, filed May 12, 1958, which issued as Patent No. 2,967,253 on January 3, 1961.

Electric hair cutting instruments, such as hair clippers, which are powered by electromagnetic vibrating motors have drive elements or fingers which are connected between the free end of the motor armature and the movable cutting blade to transmit the vibrational movement of the armature to the movable cutting blade and cause it to oscillate.

In many instruments of this kind, the drive fingers have other functions besides that of simply transmitting motion. For example, they are often made resilient in a direction perpendicular to the plane of vibration of the movable cutting blade so that the movable cutting blade may be biased into the required bearing contact with the fixed cutting blade to establish a desired cutting relationship between the blades. "In addition, the drive fingers may be made resilient in the direction of the vibrational motion of the movable cutting blade to permit relative movement in that direction in order to influence the behavior of the armature assembly under load and no-load conditions, and particularly to prevent stalling of the armature under severe cutting loads.

Although resilience in the above described direction of vibration is often desirable, it must be accomplished without appreciably affecting the path of the movable cutting blade which must oscillate along a substantially straight line to maintain proper relationship between the blades. If this is not done, the ends of the movable blade tend to whip and extend beyond the margins of the fixed blade. This is likely to injure the skin of the user.

The desired resilience along only a straight line parallel to the path of the vibrating movable blade is not easy to achieve in the drive finger since the free end of the armature assembly vibrates rapidly, and general resilience in the drive finger could cause the above described whipping action.

What is needed therefore and comprises the principal object of this invention is a drive finger which is resilient in a plane perpendicular to the plane of movement of the movable cutting blade and which permits resilient relative movement between the armature and the movable cutting blade only along a substantially straight line which is parallel to the path followed by the movable cutting blade.

These and other objects of this invention will become more apparent when read in the light of the accompanying drawings and specification wherein:

FIG. 1 is a perspective view showing the end of an armature with the drive finger attached and with arrows indicating its resilience in a plane parallel to the plane of vibrational movement of the armature.

FIG. 2 is an end elevational view, partly in section, of a portion of the armature and drive finger with a movable cutting blade attached, showing by means of arrows the resilience of the drive finger in a plane perpendicular to the vibrational plane of the movable cutting blade.

FIG. 3 is a sectional view on line 33 of FIG. 2.

FIG. 4 is a sectional view of a modified drive finger embodying the features of this invention.

3,047,948 Patented Aug. 7, 1962 Referring now to FIGS. 1, 2 and 3 of the drawings, one embodiment of a drive finger constructed according to the principles of this invention is indicated generally by the reference numeral 10. This drive finger may be formed from unitary, fiat, thin, resilient, sheet material, usually metal, and before forming may be substantially T-shaped, although that shape is not critical, and others are contemplated. For example, an initial rectangular shape properly slotted would be quite practical. As understood in the art, finger 10 is mounted to transmit vibratory motion in the directions indicated by the arrows A in FIG. 1 from a vibratory armature 20 to a movable blade 32 (FIG. 2) of an electric hair cutter.

Drive finger 10, in this particular embodiment, includes an elongated stem or arm portion 12, a base portion 16 and oppositely projecting arm portions 1414. As shown by its shape, the cross sections of the stem or arm portion 12 transverse to its direction of elongation are straight and parallel to each other so that the drive finger is resilient to forces applied to it which are perpendicular to its surface and rigid to forces applied to it which are parallel to its surface.

In vibratory motors used in hair cutting instruments, the armature vibrates, and since its thickness is not significant, the armature may be described as vibrating in a plane. Base portion 16 of stem or arm portion 12 of drive finger 10 is connected to vibrating armature 20 in such a way that stem portion 12 is resilient to forces applied to it which are perpendicular to the vibrating plane of armature 20. Consequently stem portion 12 of drive finger 10 is rigid to forces applied to it in directions Parallel to the vibrating plane of the armature and perpendicular to the direction of elongation of the stem or arm portion. The above described resilience may be used to provide the required cutting bias or tension between the fixed and movable cutting blades described below.

In addition, the rigidity of drive finger 10 in the direction described above permits stem or arm portion 12 to withstand the large inertial forces produced by the rapid vibratory motion of the armature and movable blade without bending or whipping, in a plane parallel to the vibratory plane of the armature, around its connection with the armature. The direction of these inertial forces applied to drive finger 10 is indicated by arrows C in FIG. 1.

Stem portion 12 may be bent at 13 to control the magnitude and direction of the bias between the fixed and movable blades, and this direction is indicated by arrows B in FIG. 2.

As seen, base 16 may be enlarged and provided with openings 18, so that drive finger 10 may be secured firmly to the free end of armature 20 by any conventional means such as screws or rivets 17, see FIG. 2.

The oppositely extending arm portions 1414 disposed on the free end of stem portion 12 opposite to the base portion 16 project from a common central section 22. Arm portions 1414 are bent substantially perpendicular to central section 22 to form a pair of spaced parallel flanges 24 which extend in a direction parallel to the direction of elongation of the central section 22. Since these flanges are also formed from the same resilient sheet material, they will be resilient mainly to forces applied to it which are perpendicular to their surface.

As seen in FIG. 1, this means they will be resilient to forces parallel to the vibrating plane of armature 20, see the arrows D in FIG. 3. The free ends 26 of flanges 24 in this particular embodiment are bent toward each other in a plane parallel to the plane of the common central section 22. These free ends are adapted to be secured in suitable manner, as by molding, to plastic member 30 which engages movable cutting blade 32 of the hair cutting instrument. As seen, movable blade 32 vibrates along a line or path parallel to the cutting portion of fixed blade 33.

This arrangement introduces a resilient between armature 20 and movable cutting blade 32 in the vibratory plane of the armature so that the operation of the vibrating motor under load and no-load conditions may be optimized and armature stall under severe loads may be eliminated. At the same time, since the length of the flanges 24 is small in comparison to the length of stem portion 12, any pivoting movement of these flanges around an axis defined by their edge connection to central section 22 will produce only insignificant deviations from the straight line motion of the movable cutting blade.

A modified drive finger 40 is shown in FIG. 4. This drive finger may initially be T-shaped, but in this construction downwardly facing U-shaped flanges 42 including upwardly bent arms 1414' are formed on the ends of common central section 44. The extreme ends 46 of flanges 42 are bent toward each other in a plane par allel and closely adjacent to the plane of the common central section 44. Ends 46 are adapted to be connected to a plastic member (not shown) like that described in connection with the form shown in FIGS. 1-3.

This modification in which central section 44 is closely adjacent to ends 46 of flanges 42 is useful when space limitations in a particular cutter forbid the employment of the drive finger shown in FIG. 1 with the comparatively large separation between common central section 22 of the arms 14-44 and ends 26 of flanges 24. Furthermore, despite any space limitations which may be encountered, the overall length of flanges 42 may be made equal to or greater than the length of flanges 24 in drive finger so the modified drive finger may be used to provide any desired resilience between armature and movable cutting blade 32 in planes parallel to the vibrating plane of the armature.

The invention may be embodied in other forms without departing from the spirit or essential characteristics thereof as set forth in the claims, and the present embodiment is therefore to be considered as illustrative and not restrictive, and it is intended to include all changes which come within the scope and range of the claims.

I claim:

1. In a hair cutting instrument having a fixed blade, a cooperating movable blade and a motor including a vibratory armature having a free end spaced from said movable blade; a drive finger of resilient sheet material extending between said armature free end and said movable blade and connected rigidly to said free end and to means rigidly engaging said movable blade, the portion of said drive finger adjacent said armature free end having its width dimension parallel to the plane of armature vibration whereby said portion is rigid to forces parallel to said plane and resilient to forces normal to said plane, said former characteristic effective to prevent blade whipping and said latter characteristic effective to provide cutting bias between said blades, the portion of said drive finger adjacent said movable blade extending from said first portion and having a width dimension lying in a plane generally perpendicular to said first portion and to the path of said movable blade whereby said last portion is rigid to forces tending to twist same and resilient to forces parallel to said path, said former characteristic further effective to prevent blade whipping and said latter characteristic eifective to prevent motor stall when the instrument is subjected to heavy mechanical load.

2. The combination of claim 1 wherein said last portion comprises a pair of spaced flanges having width dimensions normal to forces parallel to the path of said movable blade, the free ends of said flanges rigidly secured to plastic means adapted to seat rigidly within a recess in said blade.

3. The apparatus set forth in claim 2 wherein said flanges are U-shaped to increase the length thereof without causing a corresponding increase in a dimension of the drive finger.

References Cited in the file of this patent UNITED STATES PATENTS 1,596,294 N'orstrom Aug. 17, 1926 2,082,402 Kusnarowis June 1, 1937 2,265,932 Wahl Dec. 9, 1941 2,304,525 Andis Dec. 8, 1942 2,668,351 Andis et al. Feb. 9, 1954 2,876,538 Wahl et al. Mar. 10, 1959

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