US2928171A

US2928171A - Cutting head assembly for electric hair clippers

Info

Publication number: US2928171A
Application number: US782893A
Authority: US
Inventors: Oster John
Original assignee: John Oster Manufacturing Co
Current assignee: John Oster Manufacturing Co
Priority date: 1958-12-24
Filing date: 1958-12-24
Publication date: 1960-03-15
Anticipated expiration: 1977-03-15
Also published as: GB856396A; FR1219749A; CH359060A; DE1094152B; BE580894A

Description

J. OSTER March 15, 1960 CUTTING HEAD ASSEMBLY FOR ELECTRIC HAIR CLIPPERS Filed Dec. 24, 1958 2 Sheets-Sheet 1 Jul-Ln Us ET FllllllL March 15, 1960 J. OSTER 2,923,171

cu'r'rmc HEAD ASSEMBLY FOR ELECTRIC HAIR CLIPPERS Filed Dec. 24, 1958 2 Sheets-Sheet 2 g E algae \D Q- N O SONfiOd NI 3380i O40 SPRING TRAVEL IN INCHES j 4 I5 22 9 Z7 Z8 E25 25 8 NEW guoowu o aimdmn ml r 3 602m. Ugber I? valso afiect spring tension.

United States Pa e? CUTTING HEAD ASSEMBLY FOR ELECTRIC,

HAIR CLIPPERS John Oster, Milwaukee, Wis.,- assi'g'n'orte' John pster Manufacturing (20., Milwaukee, Wis;-,-a' corporation of Wisconsin 1 I i V 'Applicafion December 24, 1958, Serial Ne. 782,893"

l Claims. c1. so -2 21); I I

This invention relates to"- le'c'trie' hair" clipper yand refers more particularly-to improvements'in cutting-head assemblies forsuch electric clippers: I

As is well known, an electrlic hairclippei-comprises a body that provides both ahousing fbr-its'electric motor and a handle for the device, and a cuttingheadiwhich is usually readily detachably mounted on the front end of the body and which includes cooperating stationaryand movable blades having toothed cutting edges; The movable blade of the cutting head flatwis'e overlies the stationary'blade and is reciprocated remade t'o 'si'de relative to the stationary blade by means ota drivingrlever actuated by the electrictrn'oto'r' in the body of the clipper. To insure that the teeth of the blades will have'a good shearing action, the movable blad'e- -is pressed flatwise against the stationary blade by'm'eans of 'a-s'pring member secured to the stationary blade a'nd'forming a part of V the detachable cutting head. I

Heretofore it has been well'r'ecognized that the amount of force exerted by the spring rnemben inurgingthe movable blade flatwise against the stationary. blade is a critical factor in the operation of a clipper. If.the movable, blade is pressed against the stationary blade with insufficient force, the clipper does'not' cut wellsince the blades tend to be separated by hairs engagedbetween their teeth. However, if the spring member exerts excessive pressure upon the movable blade, the latter will drag so heavily against the stationary blade that the motor runs slower which-ofcourse, results-in a sluggish cutting action.

" From experience it is known that forbest results, the blades of the cutting heads with which this invention is concerned, should be held together with a minimum'of six pounds of forcefa'n'd not greatly in excess of that.

, Ideally, the tension spring used to hold the blades to:-

gether would provide and; maintain this optimum spring tension, but for many reasons this ideal condition could ice practical application of. the, principles thereof, and

not possibly be uniformly attained in production, 'and in those few instances when it was achieved, it would not be maintained during use of the clipper.

As the contacting blade surfaces wore down with use, the spring force would decrease; or it might increase if burrs developed on the blades from their operation. Variations in thickness of the film of lubricating oil would In-addition to these variables, there were'also the usual variations in the dim'ensionsof the parts at the time of manufacture. These many unpredictable factors forced the manufacturer to accept a sixteen pound top limit for the spring tension; and with that wide a tolerancefrom 'a minimum :of six pounds to a maximum of sixteenmost of the blade ase nblies left the factory with a spring tension of ten to {{twelve pounds. I As a result of this unnecessarily heavyk'spring-tension, there was undue wear on all of the moving-parts of the machine, the motor ran too slow so that the cutting action was sluggish, and because of theinereased load the motor would heat .up excessively, ofteneto the point shown ant -a u t g-hea provide-1a cutting-head'fon an. clectrie hair, clipplerofthe character; described, wherein the spring which presses the movable-.blade flatwise against the stationary'blade has a p nd' sprinatec atomb nin t e resili e .15, a torsion springwith'that of antelever mounted flat "leaf spring, with the resultthatthe; spring has a larger effegtive'lengththanthesprings, it replaces, and because of its additional, length and compound action canbe held to closer force tolerances during manufacture and maintains the desired clamping pressure upon the blades sub;-

stantially. constant despitevarying conditions of wear or lubrication of the contacting blade surfaces.

It .is.also an object .ofthis invention to provide a clipper blade tensionvspring for electric hair clippers which becopies, substantially the same space that spring members h re re; a a e req i d," which is as y m unted on thecutting head of; the clipper, and which cooperates with astrap-and with the stationary blade to defihea mounting tongue receivingVsocltet;and which, along with these advantages, provides superior performance in bias lug-the blades of the cutting head toward-one another wlth' cu ely. p determined and l ly ma nt i force.

With the above and other objects in view,

in the novel construction, combination and arrangement of, parts snbstantially as hereinafter described and more particularly defined by the appended claims, it being understood that such.. changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims. 7 V The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to they best mpde so far devised for the in which: v

Figure 1, is aside elevational view often electric hair clipper having a cutting head, embodying" the principles of t i en ion;

i e 2 is a r; J view f t s it ng bead 9 th I electricjclipper shown in Figure 1;

of the line3 -.-3 inFigure 2;

Figure 4 is a perspective view of a cutting head spring m'emberembodying the principles of this invention; 7

Figure 5 is a graph showing how little the force exerted by the spring member of this invention, illustrated at the bottom of this view, varies with change in the extent of its flexure; and i l i F gu e a is a aph- Figureil is. a verticalsectional. yiew taken on the plane similar to Figure 5 but showing how -rnuch'more the forcetofthe spring member in the conventional lprior vcutting heads, illustrated at the bottom of the figure, varied with-change in the extent oflflexure.

Referring now'rnore particularly to theaccompanying drawings, the. numeral 5 designates generally an electric hairclippercomprising .a body 6 which provides botha handlefor thecliPPfliand a ..ho. using for itsmotor, not W l ,r'em bl annua Patented Mar. 15,1960

which appear. ,as-the description proceeds, this invention resides on the front end of the body. The cutting headcom;

prises a stationary bottom blade 8 and a movable top blade 9 reciprocable from side to side across the top face of the stationary blade; A -r'ndiallypivoted lever 10 drivingly connected with the motor and the movable blade imparts the side to side cutting motion to the move able blade. Both blades have toothed front edges which coast to effect cutting by shearing the hairs caught between the teeth of the two blades as the movable blade reciprocates to carry its teeth across those of the stationary blade.

For the blades to cut.properly,-it is of course necessary that they be urged fiatwis'e against one another with their toothed edge portions in good shearing relationship. To this end the cutting head includes a spring member .13 which is secured to the stationary blade and presses down upon the movable blade. It is this springrnember and its mounting with which the invention is chiefly concerned, but before taking up the detailed'deseription' thereof --it would be well to describe the manner which the cutting head is readily removably connected to the front end of theclipper body, though this connection has be come Widely known in the h'airclipper art, Briefly, it consists of a tongue hin'gdly mounted on the body for swinging motion toward and from 'a detent defined raised or closed position, in which the tongue overlies the inclined front end of the body. A strap 16 on the cutting head cooperates with the upper surface of its stationary blade to define a slot-like socket in which the tongue is engageable, such engagement-being possible when the tongue is swung to its lowered or open position. -With the tongue in its raised or closed position, the cutting headis, of course, held in'its operative position illustrated in Figure 1. In this position the front end of the lever 10 is engaged between a pair of hardened wear shoes 18 on the movable blade, o'neat each side-of a rearwardly opening notch 20 therein, so that the lever can impart reciprocating side-to-side motionto the movable blade as thelever is oscillated by the motor.

Patents Nos. 1,888,688 and 2,182,597, contain more specific disclosures of a structure similar to thatwhich has been described in general terms up to this point.

Heretofore, the spring employed to ho'ld the blades together has been of the simple leaf spring type mounted cantilever fashion, though in plan it was substantially U-shaped with short, slightly curved legs providing the spring blades or leaves. The ends of these short blades or leaves were connected by the bight portion of the U which overlay and press against the movable blade. In cross section the bight portionwas shaped to provide a downwardly facing ridge which engaged in a generally V-shaped groove in the top face of the movable blade to constrain the same to straight line side-to-side motion, it being understood that the ends of the legs of this spring member were fixed to the stationary blade. This is the structure shown in the aforesaid Patent No..l,888,688, and illustrated in Figure 6 where it is designated by the referencecharacter S. 1

Figure 6 also illustrates the deficiency of this prior type of spring member. Because of the shortness of the spring blades provided by its legs, a very slight deflection of the legs produced a very substantial change'in the force which the spring member exerted against the movable blade. Moreover, a group of such spring members, made as nearly identical as possible by normal production methods, would vary widely in stiffness from unit to unit, due to slight variations in metal thickness, temper, and other factors. stifiest and least stiff units in a'normalfgroup of such springs are depicted by the lines designated Force "Range in Figure 6.

answer The limiting values of response for the limits, as indicated bythe Force Range lines in Figure 5 designating the response characteristics for the stiffest and most resilient units in a typical group of such spring members.

The reason for the more precise response of the spring member of this invention resides in its shape and forma-I tied.- As bestshown in Figure 4, the spring member 13. comprises a pair of identical leaf springs 22 each doubled upon itself into a looped or substantially U-shaped formation having a short inner leg 23 which is fastened to the stationary blade, a longer outer leg 24 and an arcuate bend or medial portion 25 connecting the inner and outer legs. These two leaf springs are connected at the free ends of their outer legs 24, by a cross bar 26, and preferably the two leaf springs and their connecting cross bar are one integral stamping of hard Phosphor bronze or similar metal. The spring member of this invention, like its predecessor isthus generally U-shaped in plan, and the cross bar 26 which forms the bight of the U is so shaped in cross section that it provides a downwardly facing straight ridge 27. This ridge engages in a V-shaped groove 28 in the top face of the movable blade to guide and constrain the same to straight line reciprocating motion parallel to its cutting edge.

The securement ofthes-pring member to the stationary blade is exceptionally rigid by virtue of the fact that the short inner legs of its two leaf springs are clamped between the stationary blade and the end portions of the socket forming strap 16.; Screws 38 which pass through the stationary blade from the underside thereof, and through the innerlegs of the leaf springs are. threaded into tapped holes in the strap to secure these parts together'. The medial portion 31 of the strap is held spaced from the outer face of the stationary blade by the interposed inner legs of the leafsprings so that the inner legs cooperate with the strap and the stationary blade in defining the tongue receiving socket, but preferably the medial portion of the strap is outwardly offset, as shown, to increase the size of the socket. Attention is directed to the fact that by virtue of the shape of the leaf springs 22 they have a compound spring action. They function not only as ordinary cantilever mounted leaf springs, but also have the action characteristic of a torsion spring, since the bends 25 which connect their legs are in fact semi-torsion springs. It should also be noted that the anchored ends of the long outer legs 24 are spaced a substantial distance above the top face of the stationary blades to which the short inner legs are clamped. As a result, the points from which the outer legs act to' press down upon the movable blade are higher than they were before so that more of the spring force applied to the movable blade is exactly downward, and practically none ofv it acts horizontally, i.e. in the plane of the blades.

It should probably also be pointed out that at the time the spring member13 is secured to the stationary blade, the movable blade is not in position, and that at th1s time the cross bar 26 does not even contact the top faw of the stationary blade. Accordingly, the entire sprmg unit is in its relaxed unbiased condition, but the space between the underside of the ridge 27 on the cross bar and the top face of the stationary blade is less than it is when the movable blade is slid into position. It is thus the insertion of the movableblade between the spring and the stationary blade which tensions the spring From the foregoing description taken together with the accompanying drawings, it will be apparent that this 1nvention provides a solutionto a problem that has long erplexed the makers of electric hair cllppers, namely, how to reliably achieve and assure the maintenance of optimum tension in the springs used to hold the cutter blades together; and that it solves this problem without entailing any change in the cutter blades or the general .O galliaation of the cutter blade assembly. It should also be apparent that this accomplishment is brought about by the simple expedient of giving the leaf springs 22 the described U-shaped formation which increases their effective length without requiring additional space and raises the points from which the spring force is applied;

and that by virtue of the increased effective length of the leaf springs, it has been possible to reliably achieve a predetermined spring tension or force during manufacture and to maintain substantially that same tension or force during use.

What is claimed as my invention is v 1. In a motor driven hair clipper of the type having to the stationary blade, in flatwise engagement therewith directly behind the movable blade, with the curved medial cooperating stationary and movable blades with toothed front edges, and wherein the movable blade flatwise overlies the stationary blade and is laterally reciprocable relative thereto, spring means urging the two blades flatwise toward one another and also readily removably locating the movable blade upon the stationary blade, said spring means comprising: a pair of substantially identical leaf springs each doubled upon itself into a Ueshaped formation with a short inner leg and a longer' outer leg overlying but spaced from the inner leg and connected thereto by an arcuate bend so that the outer leg may be flexed toward as well as from the. inner leg; means clamping the short inner legs of both leaf springs directly to the stationary blade with the ends of said inner legs adjacent to the rear edge of the movable blade and at a level below the top of the movable blade, and the long outer legs disposed over the top of the movable blade; a cross bar connecting the ends of the long outer legs and bearing down upon the movable blade to press the same against the stationary blade; and slidingly interengaging guide means on the cross bar and the movable blade constraining the movable blade to lateral reciprocation, engagement and disengagement of said guide means requiring only relative lateral motion of the blades so that .the blades may be quickly and easily disassembled and reassembled.

2. A cutting head for electric hair clippers comprising: cooperating stationary and movable blades in flatwise overlying engagement; spring means clamping said blades flatwise together and holding them in predetermined cooperative relationship, said spring means being an integral stamping formed to have a pair of leaf springs each doubled upon itself to provide a short inner leg and a longer outer leg overlying but spaced from the inner leg and connected thereto by a curved bend, and a cross bar connecting the extremities of the longer outer legs a of the two leaf springs; means securing the short inner legs of both leaf springs directly to the top of the sta-' tionary blade with the ends of the inner legs directly behind the movable blade and at a level below the top of the movable blade, the cross bar pressing down upon the top of the movable blade; and slidin'gly interengaging guide means on the cross bar and the movable blade constraining the movable bladeto lateral reciprocation.

3. In a motor driven hair clipper of the type having cooperating stationary and movable blades with toothed front cutting edges, and wherein the movable blade flatwise overlies the stationary blade and is reciprocable laterally relative to thestationary blade, means defining the position of the cutting edge of the movable blade with respect to that of the stationary blade and urging the movable blade flatwise toward the stationary blade to press the cutting edge portions of the blades flatwise toportion of each spring leaf remote from the front cutting edges of the blades and spacing the outer and inner legs from one another; a cross bar connecting the free ends of the longer outer legs of the two spring leaves, overlying and pressing down upon the movable blade; and slidingly interengaging guide means on the cross bar and the movable blade constraining the movable blade to lateral reciprocation with its cutting edge in a predetermined posi-' tion with respect to that of the stationary blade.

4. The motor driven hair clipper of claim 3 further characterized by a strap having end portions overlying the inner legs of said spring leaves and held spaced from the adjacent face of the stationary blade by them, said strap cooperating with the inner legs of the spring leaves and with the adjacent face of the stationary blade to define V a socket in which a tongue is engageable for mounting the blade assembly on a clipper.

5. In a motor'driven hair clipper of the type having cooperating stationary and movable blades with toothed front edges, and wherein the movable blade flatwise overlies the stationary blade and is laterally reciprocable relative thereto, means defining the relative positions of the toothed front edges of the blades and urging the two blades flatwise toward one another, said means'compris ing: a pair of substantially U-shaped spring leaves, each having a short inner leg and a longer outer leg; means securing the short inner leg of each spring leaf flatwise to the top of the stationary blade, behind the movable blade, and with the bight portion of the spring leaf rearmost, so that its longer outer leg projects toward the front cutting edges of the blades; a crossbar connecting the outer ends of said longer legs of the two spring leaves and bearing upon the movable blade with a force de pendent upon the extent the spring leaves are flexed by the insertion of the movable blade between the cross bar and the stationary blade, the U-shaped form of the spring leaves providing them with substantial length so that slight variations in the distance between the underside 'of the cross bar and the top face of the stationary. blade do not seriously affect the force with'which the spring leaves hold the blades together, whereby said force is more easily predetermined during manufacture and remains substantially unchanged during use; and slidingly t interengaging guide means on the cross bar and the movable blade constraining the movable blade to lateral reciprocation with its cutting edge in a predetermined position with respect to that of the stationary blade.

References Cited in the file of this patent UNITED STATES PATENTS