US2395495A - Dry shaver - Google Patents

Description

Feb. 26, 1946. MURPHY 2,395,495

DRY SHAVER Filed July 5,- 1943 Patented Feb. 26, 1946 DRY SHAVER Thomas J Murphy, Stamford, Conn.

App c tion July 5, 3, S r alNo- 93, 43.

8 Claims.

Thisinvention relates to dry shaving devices of the type includingoneor morerows of cooperating shearing'teeth constructed and mounted in ahead comprising. arow of guard teeth movable over the surface of the'skin and an inner movablev cutter cooperating with the guard teeth to, perform the cutting operation, the movable teeth being driven by an electric motor mounted in a casing forming theoperating handle and on which the cutter head is mounted.

It is an object of the, invention to provide A an improved construction and arrangement of the teeth whereby extremely strong rigid guard or outer cutter teeth may be secured, with a minimum thickness whereby the devicewill operate more efiectively and efficiently in rapidly cutting the hairs close to the skin surface without injuring or irritating the skin, or causing other dis, comfort.

Most dry shaving devices of this general char acter include outer guardmembers or outer shear members which are provided with transverse hair passages through which the hairs must pass to the shaving position asthe implement is passed over the skin surface. These teeth have been made relatively long in order to secure sufiicient cutting edge and to insure that the hairs are brought to a cutting edge as the implement moves over the face, and to. prevent the hairs moving past or beyond and oil the cutting edges as the implement is moved over the surface during the long dwell at the opposite ends of or reversal of the reciprocating movement of the reciprocating cutter, which is involved in the operation by the motors commonly employed, before the movable cutter has a chance to grip or shear them. However, in order to secure a close shave it is necessary thatthe teeth be very thin, but when the thickness of such long teeth is reduced they are necessarily rendered less rigid and are therefore apt to. yield under pressure against the skin to press too tightly against the movable cutter,

and are also apt to yield in the shearing operation so that the cutting edges of the stationary and movable teeth may separate slightly, interfering with the proper shearing operation and giving very unsatisfactory shaving as well as causing pull on the hairs and severe irritation and discomfort. To overcome these objections a compromise had to be reached by making the teeth thicker so as to give them sufficient rigidity and stiffness to retain their position. This meant that the shearing edges are necessarily moved outward away from the surface of the skin so that it is impossible to secure the desired close shave required to be at all comparable to that possible withthe standard straight razor blade.

I have found that if the free lengthof the teeth, that is the length of the outing, edge of the teeth or hair, passage, is approximately-that of the diameter, of the hair or only slightlygreatel', the thickness: of the guard teeth. may b reatlyareduced and still retain the required. ri id y and stiffnesszsothat the teeth remain in their proper position and are not: forced: out of this p f on durinezthe cuttingoperation, I havealso found that the dwell: of them v b e cutter at the opposite ends or reversing positions. o tsstroke is greatly. reduced. and brou hto a m n mum. p eferably actically zero, the: ha rs can be at: .fectiye y cut w th th se short teet en with relatively rapid movemen of th head: o er the sur ac of the s in because t e d l or period o ime when th z nne cutter. i not mo in not, sufficient to ermit them fl -n ss thro h he pa sa eswithout bein out With h s struc ure and arran ement the passa or more tr ct the shea in z ne; i l onta n on o e ha r at a. t me, r at y dec asin the w r equired r operat ng the movable c t r nd. at he ame e educinet es stance w ich must eoverme y a gua d. or stati nary too h a a given shearing operation thus still further reducing the, tendencyof the shearing operationto force theguard or stationary tooth out of posi:- tion or reducing the tendency to separate them, and thus reducing the pulling and irritation of the This construction and arrangement also permitsthe use. of much thinner teeth, per

mitting. bringing. of the shearing edges closer to the surface of the skin and therefore giving a much closer shave with less irritation. In fact the thickness of the, teeth can be of the order of that of the standard straight razor blade,

These and other feature and advantages of'the invention will be more clearly understood from the following description in connection with the devices illustrated in the, accompanying drawing forming a part of this specification, It is, however,- to be understood that I am not limited to the specific details shown but may employ variou changes and modificationswithin the scope of the invention.

In this drawing-:

Fig; 1 is a side elevation on an enlarged scale of one section ofthe casing showing a portion of the motor and the cutter head in elevation, but with' parts of thedriving connection to the movable cutter broken awayto more clearly show the construction;

Fig. 2 is a top plan view of one form of the cutter head Fig. 3 is a transverse section through the cutter head;

Fig. 4 is a top plan view of a portion thereof;

Fig. 5 is a section similar to Fig. 3 showing a modified arrangement; 7

Fig. 6 is a top plan view of a portion of the arrangement of Fig. 5;

Fig. 7 is a section similar to Figs. 3 and 5 showing another modification;

Fig. 8 is a top plan view of a portion of the arrangement of Fig. 7;

Fig. 9 is a section showing still another modification;

ably soldered to the blocks, and to insure sufficient solder for the operation tapered pockets [6 may be provided in the sides of the blocks l4 into which the solder may run and from which it may pass to the contacting surfaces between the side plates and the blocks. After this operation is completed, the connecting strip may be sawed or cut away as described in the prior patent above noted. I

At the upper or outer edges of the side mem- 18, the outer surface l9 being the skin contacting Fig. 10 is a top plan view of a portion of the arrangement of Fig. 9, and

Fig. 11 is a detail View looking toward the edge of a row of shearing teeth of each of the forms shown, the view being taken as indicated by line Hl| of Figs. 3, 5, 7 and 9.

The device comprises a' casing'or housing I enclosing an electric operating motor 2.. I prefer to use a motor of the type disclosed in my prior patents, No. 2,203,695, June 10, 1940, and No. 2,288,203, June 30, 1942, as such a motor gives a relatively long stroke with a minimum dwell, the dwell being practically zero at the opposite ends of the reciprocating movement, or that is at the point of reversal of this movement. The stroke given to the movable cutter should be greater thanthe pitch of the outer stationary teeth, and the greater the better. With the motors mentioned a stroke'of one-eighth of an inch or even more can be secured. This motor has a :1

reciprocating or oscillating driving element 3 from which there is any suitable type of drive connection 4 to the reciprocating cutter 5 of the cutter head 6 mounted in any suitable manner in the end of the housing I, as for example in a suitable transversely extending groove I in which it is held by suitable securing means (not shown). I amnot limited to the specific driving connection 4 shown, but that indicated comprises a threaded stud 8 mounted on the reciprocating driving element B and embraced by a hollow pin 9 slida'ble on the stud 8 and provided with a flange I 0 against which a spring ll may react tending'to shift the pin 9 against the cutter 5,

'thispin being provided with a rounded end l2 seating in a recess I 3, formed in the lower wall of the cutter by pressing inwardly or upwardly a portion of this wall, there being left sufficient "clearance or play between the sidesof the pin and the recess to permit limited rocking movement of the rounded end of the pin in the cutter required by the reciprocating movement. The action of the spring I l and the pin also tends to hold the movable cutter against the inner or undersides of the outer guard teeth of the head to maintain the teeth on the movable cutter in proper cutting or shearing relation to the teeth of the outer or stationary cutter.

. The cutter head shown comprises a pair of longitudinally spaced mounting or supporting blocks M to the opposite sides of which are secured the side members or plates 15. After being finished these plates I5 are clamped against the opposite sides of the blocks [4, which at this time may be connected by an integral connecting strap (shown in my prior application Serial No. 412,055, filed September. 2-1, 1941, now Patent No. 2,325,267 is sued July 27, 1943) and then secured to the blocks by suitable solder or other means, but are prefersurface during the shaving operation, and as indicated, it is preferred that these surfaces I9 be slightly backward or downwardly inclined from the free ends of the teeth l8, as it is found this gives a better shaving effect with less irritation than where the skin contacting surfaces are flat or straight across. This inclination of the surfaces is preferably about ten degrees, although it is not limited to this,'and the inclination permits'a certainamount of rocking of the cutter head on the skin surfaces during its back and forth movement on this surface during the shaving operation without removing either set of cutter teeth from the surface'of the skin and thus interfering with the shaving operation.

The teeth [8 of the outer or stationary member are made very short, the depth of the notches 20 being such that the length of the cutting edge.

of the teeth, indicated at 2|, is substantially the average diameter of the hairs, which is from about .0035 in. to .006 in. so that the teeth may be made very thin, it being possible to make this thickness indicated at 22 of the order of that of the edge portion of a standard straight razor blade. In an arrangement such as that shown in Figs. 3 and 4, where there are two sets of teeth is separated by a longitudinal slot 23 with the free ends of the teeth extending toward each other so the device will shave in both directions as it is moved back and forth over the surface of the skin, it is preferred that the free ends'of the outerstationary teeth 13 overhang the free ends of the inner movable cutter teeth 24 .on the inner cutter 5 by a slight amount, as indicated at 25, this overhang being preferably about .003 in; or .004 in., so as to prevent irritation of the skin by the free ends of the movable teeth 24. That is, the full depth of the slots will be approximately the average diameter of the hairs which is from about .0035 in. to .006 in. plus the slight overhang of about .001 in. or a little more to insure the hair is fully entered into the slot so that the full diameteris severed and the possibility of partial cutting and consequent irritation or pulling is eliminated. The slots between the teeth 24 in the movable cutter are preferably extended the full length of the teeth as indicated. The slot 20 between the outer or stationary teeth is preferably about .015 to .018 in. wide and the width of the teeth [8 is preferably not less than W about .012 in. to .015 in. so they will not stick into the skin or irritate it. The width of the slot 23 between the free ends of the two sets of teeth [8 is preferably about .060 in.

By using the type ofmotor indicated in my prior patents as above noted, the length of the stroke of the inner cutter 5 can be made relatively lon that is about one-eighth of an inch or even more, with a minimum dwell at the opposite ends of its reciprocating movement. Themovementis therefore about four or five times the; pitch of aeecgeea th'caouterv teeth. I 8 'I-Ioweven-if .thedwell'is very short; a: shorter :str-oke may ber'used; butcitshould not be: lessuthanthe pitcher; theouter teeth and it-i-sca' great advantageqto us'ea long strokeas bycthis a. greater velocit'ywis secured with a better cutting: effect] as when" the cutterggetsi upto a good speed 1 iniits movementit has: a much better cutting effect i'than where: there is a slow speed. The :width .OffthB inner movable: cutterateeth 24. is preierablywider thanthe space crslots 2i! between the. outer-.or stationary. teeth as indicated in Figll; .It.is also preferredthatthe spacing of'these cutter teeth or. theirpitch is not a.multiple; of: the: spacingof thezouter teeth so that they donotJalLcut atlthesame time but;cut in succession, as. this reducesrthe power required; thus reducingthe size oi the motor andalso gives aabetterand more; reliablecuttin eiiect; The thickness of the inner-or cutter teeth, indicated at.26,Fig. 3... is preferably about .025 in., although this" may vary. It is preferred that the side walls of: the inner cutter 5 be. relieved. as shown at. 27, leaving a longitudinallbearing rib or strip 28 to engage and be guided bythe inner walls of the sideplates I5. It is also. preferred that these guide strips 231be located adjacent the top edges of. the sides of thecutter and that there be only one of these strips on each side; the remainder ofJthe side walls below these strips and the bottom wall of the cutterbeingspacedaslight dis tance from the side plates I5 and, the lnonnting blocks Mias shown. This permits the movable teeth 2t": to properly engage and seat themselves against the inner or under surfacesof the outer of? stationary teeth l8 to insure the proper coaction. to securethe most effective cutting or shearing. operation, as this construction and arrangement permits slight lateral rocking movement of the inner cutter. 5 so that. the teeth 24 can" properly seat against the outer teeth. It is alsopreferred to cut away the longitudinal upper edges or corners ofthe inner cutter as shown at 29 so. that: should the cut hairs get in between the two cutters they cannot pass down between the bearing 'surfaces between the inner and outer cutters and cause binding. The bearing surfaces or ribs 28: seal the sides between the members and prevent the cuttings getting down between the sides'of the inner and outer cutters, as well as keep thetips of the inner cutter teeth in line back of. the outer teeth. That is, these ribs preventany. lateralor side movement during shav ing-while absence of such ribs at the lower part of the inner cutter. Willpermit all teeth tccontact'pr-operly and perfectly because of the clearances at the lower part of the inner cutter. Thi arrangement is very important with the very short teeth ofthe cutter head of this invention aswith such short teeth the inner element or cutter-.mustfit the outer element accurately.

Inthe form shownin Figs. 5 and 6 there is a stationary guard or comb 3!] mounted between the two' laterally spaced sets or rows of cutter teeth; This guard prevents the flesh entering between the ends of. the teeth and prevents irritationof. the skin. With this guard itis unnecessary to providethe overhang 255 of the free ends of the outer teeth I8 over the free ends of theiinner teeth. althoughthey may overhang a slight amount if desired. The free edge of the guarded may be plain or provided with a series of: transverse teeth 31. The teeth if used are preferably. spacedto correspond with the spacingrof" the outer? teeth I8, although the space betweentthe'. teeth? could be. less than that of teeth I 8 The corners: 32;. of? the 1 guard 3 are;- preferably leftrisubstantially square, although they would? be given: a: slightrounding by the. bufiingoperation; as'whemsquare theytare more "efiective iIi'ilaiSiIl'g the: hairs from the surface; of.the.sl intso::.that they "are; more 'nearlytat right angles to. the: sur face as: they enter thenotohes betweenitlie. teeth l8. and thereforeJare: in-the best'position for-the shearing operation; There is a definitenew-icom bination andji special coaction between. the; stae tionaryguard and the short outer: teeth Was the guard prevents the thin teeth .from' sticking into or, irritating the skin and'the: closenessof the-shavev may be determined by the relative ipos sitions-ofthe outer-surface of teeth l8 andthe free-edge of the guard, as for examplerbycthe amount the free edge of the guard is extended above the skincontacting outer face of the teeth I8. Thus by relative location oi-th'e free edge ofthe guard with respect to the outer or skin contacting surface of" the teeth I8 the smooth-,- ness ofthe shave can be governed; The guard is preferably from about 20 to .025 in. thick.

In the form shown in Figs. 9 and. lo the inner cutter 5 issubstantially the same as that in Figs: 3 andB'b-ut instead of having two rows of outer stationary teeth 18 the overhanging. free edge portion 33 of one of the side plates I50. is; left plain andsmo-oth with no teeth but. is spaced from the free ends of the teeth I3 on the other side of the separating slot 34. Thus the plain edge portion 33 really acts as a guide and guard for the set of operating teeth similar in efiect to the intermediateguard 30'of Fig. 5, and it: also helps to determine and maintain the proper angle of the head on the skin as does each set of cutters with respect to the other set ofthe arrangements ofFigs. 3 and 5.

In Figs. 7 and 8' the overhanging edge 3510f: one side plate 36 isgwider than in the previous forms but at its freeedge is provided with short cutter teeth I8 as in the other forms. However, theopposite side plate 31 is provided with either a plain or toothed edge 38 corresponding to that of the guard 30 of Fig. 5 and it may be given a slight overhang as indicated at 39. equal in amount to about as offlan inch or even more if desired. This helps to raise the hairs from' the skin to the proper cutting position. If teethare provided they are preferably-of the same pitch as the stationary cutter teeth I8:.with thendepth of slot or notch between themirom about .025 to .030 in. This functions substantially the same as the guard 30 except it is usedwith only a single row of cutter teeth and it has the same'effect of raisingthe hairs-to the cutting position and preventing irritation of 1 the skin'by the thin: teeth I8. It also may be used to control the closeness of the shave depending on therelation ofits outer or free surface to the outer surface of the teeth l8; that is by makingit higher. or lowerv it.can govern the closeness of theshaveand thesinooth-- ness of theshaving operation. In this case the inner movable cutter 4a is shaped somewhat different from cutter'5 of the'other form, although thefunction and operation is practically. the same; Inthis cutter there are teeth 4| only on one side but the sides of the substantially U-shaped cutter member are relieved as shown at 2! the same as in the other form to provide the two bearing ribs or strips 28. 'Ihere may or may not be a slight overhang of the free ends of'the outer teeth l8 over the free ends of the-inner or movable teeth 4I, but with thisguard an overhang is unnecessary. l

'It will be evident the drawing is'enlarged and not to scale. Some of the dimensions that 'may be used although the device is not limited to them, is to make the height 42 of the head about threeeights of an inch, the width 43 about one-fourth of an inch and the thickness of plates l about one-thirty-second inch, the slot 44' (Fig. 7) is preferably about .015 to'.025 inch wide. The walls of the inner cutter 5 could be about in. thick and the relief 21 approximately .005 in.

It will be understood from the above the shorter the outer or stationary teeth the greater will be their strength and rigidity with a given thickness and therefore with a short tooth the same strength and rigidity can be secured with a much thinner tooth, permitting much closer shaving. Theoretically the depth of the slots between the teeth in the outer cutter, or that is, the length of the working or cutting edge, need not be greater than the diameter of the hair or whisker being cut which by measurement has been determined to be from about .0035 to about .006 in.,' but it is preferred to make it slightly greater to insure the whisker is wholly in the slot when out so the full diameter is cut and pulling or irritation by partial cutting is eliminated. For best results these short teeth should be combined with a minimum dwell or rest of the inner or movable cutter at the opposite ends of its reciprocating movement, and

a relatively long stroke of the inner cutter gives.

still further improved and more efficient operation.

Another advantage of the very short teeth in the outer cutter is the beard raising function of the bottom or base of the slots between the teeth while moving the cutter against the beard. At the same time considerable discomfort is eliminated for the following reason. If the teeth are short, that is substantially the average diameter of the hairs of the beard, the thickness of the outer tooth at its base may be made substantially the same as that of the rest of the cutting length of the tooth. Consequently the hairs raised to a vertical position by the base of the slots will be cut oif at the surface of the skin leaving no stubble to further impinge against the bases of the slots to cause discomfort as the shaving is continued.

Having thus'set forth the nature of my invention, what I claim is:

1. A dry shaver comprising an outer shear member provided with a series of thin overhanging teeth at its outer edge spaced by notches of sufficient width for passage of hairs between the teeth, an inner movable shear member having teeth at the inner sides of the first teeth and movable transversely thereof to cooperate with the first teeth to cut the hairs; and the length of the zone of cutting of cooperating teeth comprising the distance from the bottom of .the notch between outer stationary teeth to the tip of the inner movable tooth of the respective shear members being only slightly greater than the diameter of the hairs.

2. A dry shaver comprising an outer shear member provided with a series of thin'overhanging teeth at its outer edge to move over the surface of the skin, said teeth being spaced by notches of'sufiicient width for passage of hairs between the teeth, an inner movable shear member having a series of laterally spaced teeth at the inner sides of the first teeth and movable transversely thereof to cooperate with the first teeth'to cut hairs, the lengthof the zone of cutting of cooperating teeth comprising'the distance fromthe bottom of the notch between outer stati'onary'teeth to the tip of the inner movable tooth of the respective shear members, and the length of the outer teeth, being only slightly greater than the diameter of the hairs to increase the rigidity of the thin outer tooth, and astationary guard extending parallel to said ed e of the outer shear member and spaced a short distance from the free ends of the outer teeth.

3. A dry shaver comprising a mounting member, plates secured to the opposite side of said member and extending above the top thereof, said extending portions having overhanging edges provided with a series of spaced thin teeth extending transversely of said edges and with their outer surfaces inclined downwardly and outwardly from the free ends of the teeth, said teeth being arranged with the free ends of those on one plate extending inwardly toward those on the other plate and spaced therefrom to provide a longitudinal slo-t' between the series of teeth, said teeth in each plate being spaced by notches of suflicient width for passage of hairs between the teeth, an inner movable cutter having a series of laterally spaced teeth at the inner side of each series of outer teeth and movable transversely thereof to cooperate With'the first teeth to cut hairs, and the zone of cutting of cooperating teeth comprising the distance from the bottom of the notch between outerstationary teeth to the tip of the inner movable tooth being only slightly longer than the diameter of the hairs to give increased rigidity to the thin oute tooth and minimum of irritation. V

i. A dry shaver comprising an outer shear member provided with a series of thin overhanging teeth at its outer edge of substantially .012 y to .015 in. in width spaced,by notches of substantially .012 in. to .018 in. wide, an inner movable cutter having a series of laterally spaced teeth at the inner sides of the first teeth and movable transversely thereof to cooperate with the first teeth to cut hairs, and the length of the zone of cutting of cooperating teeth comprising the distanoe from the bottom of the notches between the outer stationary teeth to the tips of the inner movable teeth being only slightly longer than the diameter of the hairs, viz. .0035 to .006 inch.

5. In a hair cutter, a skin contacting member adapted to pass over the skin for cutting hair therefrom, said member being provided with sets of opposed thin teeth having free ends extending toward but not reaching each other and separated by slots of sufficient width for passage of hairs between the teeth, an inner movable cutter provided with spacedsets of similarly opposed teeth having free ends extending toward each other operating at the inner sides of the other teeth and cooperating therewith to cut hair from the skin as the cutter is passed thereover, and the length ofthe cutting zone of cooperating teeth comprising the distance from the bottom of the slots between outer stationary teeth to the tip of the inner movable tooth being only slightly greater than the diameter of the hairs.

6. A cutter head of the character described comprising a mounting member, side members in the form of plates secured to the opposite sides of the mounting member and extending laterally therefrom, the free edge of at least one of said extensions being provided with a series of thin overhanging teeth spaced by notches of sufficient width for passage of hairs between the teeth, a movable cutter member of generally rectangular U-shape mounted to reciprocate between said side members and having narrow bearing strips adjacent the upper edges of its side arms bearing on the side plates, the outer surface of said movable cutter member being relieved below said {bearing strips around said member from one strip to the other so as to be spaced from the side plates and the mounting member, and the free edge portion of one of the sides of the movable member having a row of cutter teeth at the inner sides of the row of first mentioned teeth and cooperating therewith, the length of the cutting zone of cooperating teeth comprising the distance from the bottom of the notches between the outer stationary teeth to the tip of the inner movable tooth being only slightly longer than the diameter of the hairs.

7. In a cutter head, a body having a pair of spaced toothed edges arranged with the free ends of the teeth extending toward but not reaching each other and separated by notches of suflicient width for passage of hairs between the teeth, a cutter in the body movable relative thereto in a direction transversely of the teeth and provided with cutter teeth to cooperate with the first teeth for cutting hair, the length of the cutting zone of cooperating teeth comprising the distance from the bottom of the notch between outer stationary teeth to the tip of the inner movable tooth,

and the length of the outer teeth, being only slightly longer than the diameter of the hairs to give increased rigidity to the thin outer teeth, and. a guard between said toothed edges and spaced therefrom to prevent the flesh of the user entering between the spaced toothed edges of the body- 8. A dry shaver comprising an outer shear member provided with a series of thin teeth at its outer edge spaced by notches of sufl'lcient width for passage of hairs between the teeth, an inner movable shear member at the inner sides of said teeth and movable transversely thereof to cooperate with the teeth to cut the hairs, and the length of the cutting zone of the cooperating members comprising the distance from the bottom of notches between teeth in the outer member and the tip of the movable inner member being only slightly longer than the diameter of the hairs, viz. .0035 to .006 inch.

THOMAS J. MURPHY.

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