US3103743A

US3103743A - Shape and proportions of shearheads

Info

Publication number: US3103743A
Application number: US106260A
Authority: US
Inventors: Kobler Victor; Kobler Werner
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-11-18
Filing date: 1961-04-28
Publication date: 1963-09-17
Anticipated expiration: 1980-09-17
Also published as: CH380576A; DE1155366B

Description

Sept. 17, 1963 v. KOBLER ETAL SHAPE AND PROPORTIONS 0F swamps Filed April 28. 1961 Claims priority, application Switzerland Nov. 18, 1960 3 Claims. (Cl. 30-34) This invention relates to dry shaving razors and more particularly to a dry shaving razor of the type having at least one external transversely slotted shearcomb and an elongate shearhead which is circularly bent in longitudinal direction and has a movable inner cutting blade.

In known razors of this type certain standard sizes have been established for the radius of curvature, for the number of slots and the length of chord of the shearhead, which were considered as optimum with respect to manipulation of the razor and to efficiency of the shearhead. The external shearcomb surfaces thus usually have a length ranging from 30 to 35 mm. and a number of slots within the limits of 28 and 32, while the radius of curvature is approximately 75 mm. The main advantage of this known type of shearhead construction has been found to consist in that, during shaving, the shearcomb slightly depresses the particular skin portion and owing to its curvature is able to stretch the skin, which fact results in an erection of the hairs to a position in which they can be safely cut in close proximity to the skin. This quite intelligible theory, however, has not been sufliciently confirmed in actual practice. Tests have shown that on the one hand the distance between the outer shearcomb ends and the middle tangential plane at the summit of the curved shearcomb, which distance is determinative for the depth of depression of the shearhead, is too small in known shearheads to be able to cause sufficient stretching and thus tensioning of the skin. Frequently, some stretching of the often slack skin but without any elastic tension thereof only is obtained. On the other hand, the length of the shearcomb and thus the surface of contact of the shearcomb have proved to be too small for maintaining, if at all obtained, any tension on the skin.

The object of the present invention is to provide a dry shaving razor having improved cutting characteristics. According to the invention, the external surface of the shearcomb extends through a sector angle of at least 30 and the distance between the outer ends of this surface and a tangential plane through the summit at the center of this shearcomb surface amounts to approximately twice the distance of the ends of a middle section of the shearcomb from the tangential plane, which section comprises at least 28 transverse slots.

The relatively large distance of the ends of the shearcomb surface from the middle tangential plane permits a correspondingly deep depression of the shearhead into the skin and thus an actual tensioning of the skin while the comparatively great length of the shearhead affords a surface of contact which results in the maintenance of the obtained tensioning of the skin.

The invention will now be more particularly described by way of example with reference to the accompanying drawing, in which a fragmentary view of a dry shaving razor according to the invention is shown.

Referring to the drawing, numeral 1 represents the casing, serving as handle of an electric driving motor. An elongate shearhead 2 comprises an outer shearcomb 4 and a toothed movable internal cutting blade 4a, and is supported at one end of the casing 1. The casing 1 is slightly tapered towards the end carrying the shearhead, hair catching flaps 3 adapted to be tilted downwards being linked to the lateral walls of the casing 1;

tates Patent "ice the external surfaces of the flaps 3 are approximately in alignment with the associated lateral surfaces of the nontapered portion of the casing. The arcuate elongate shearcomb 4 has continuous transverse gaps 4b provided between webs 4c of roof-shaped, curved cross-section. The open end faces 5 of the external shearcomb 4 diverge outwardly on the cover plate of the tapered casing 1 from the bottom of the shearcomb at an angle, so that the shearcomb in its outer periphery is considerably longer than at its bottom; in the example shown this external length of the shearhead is even somewhat greater than the maximum width of the casing 1. The shape of the hair catching flaps 3 is selected to conform to the tapered portion of the casing 1 and the outwardly open end faces 5 of the shearhead, whereby the flap end 3a which abuts against the outer edge of these end faces of the shearhead practically ends into a sharp edge.

The dimensions of the shearhead shown are selected so that this head comprises for example 38 transverse gaps or slots 411, when having a chord length S of the external shearcomb surface of approximately 45 mm. and a radius of curvature of about mm. (which data correspond to a sector angle a of about 40). The distance a between the end of the external shearcomb surface and the tangential plane (3 through the longitudinal center of this surface is approximately twice as great as said distance b between the tangential plane 0 and the ends of a middle portion having the length L and comprising 30 transverse gaps 4b. Since neither the width of the transverse gaps 4b nor the width of the transverse webs 40 can be made of any desired narrow size, the said ratio of distance of a=2b is approximately obtained in any case where the distance b is measured at the ends of a middle portion having a number of gaps between 28 and 32 and the sector angle of the shearhead ranges from 30 to 40.

The desired effect, however, will be also obtained in case the external surface of the shearcomb is not provided with transverse gaps extending until its ends and in case not all transverse gaps represent transversely continuous slots; it is only necessary that the middle section L has a number of cutting edges corresponding to the mentioned minimum number of gaps, since this middle section must undertake the main portion of the cutting work of the shearhead, while the end portions mainly cause the tensioning effect of the shearhead.

We claim:

1. A dry shaving razor having a casing serving as a handle; an elongate convexly, circularly curved shearhead mounted on one end of said casing and being comprised of at least one external transversely slotted shearcomb, and a movable cutting blade Within said shearcomb, said shearcomb having an upper surface having a radius of curvature of about 75 mm., said shearcomb being comprised of a middle portion having a length ranging between about 30 to 35 millimeters and having approximately 218 to 32 of the transverse slots, and of two end portions one at each end of said middle portion, the distance between the outer ends of the surfaces of said end portions and a tangential plane through the center point of the topedge surface of said middle portion being substantially twice the distance between the said tangential plane and the ends of said middle portion of said shearcomb, whereby in shaving the soft parts of the face said shearhead may be pressed against said parts sufficiently strongly as to provide sufficient stretching of the skin with opening of the pores to attain satisfactory close shaving without the outer ends of the end portions of said shearhead coming in contact with the face.

2. A dry shaver according to claim 1, and in which the portion of said-shearhead, adjacent said casing, is longer than the corresponding dimension of Said casing so as to have portions which extend beyond said casing at each end adjacent said handle, and hair-catching flaps pivotally mounted on said handle at points spaced from said extending portions and extending over the ends of said shearhead and having portions extending beneath the extending portions of said shearhead, respectively.

3. A dry shaver according to claim 1, and in which said shearhead, at its ends, flares outwardly from the handle toward said upper surface of said shearhead, and hair-catching flaps mounted on said handle at points spaced from said shearhead and extending over the flared ends of said shearhead, respectively.

References Cited in the file of this patent UNITED STATES PATENTS Meyer Dec. 29, 1936 Jones June 4, 1940 Jones June 23, 1942 Kobler et a1 July 10, 1945 Kobler et a1 Sept. 23, 1952 Kobler Mar. 27, 1956 Kobler et al. Nov. 27, 1956 FOREIGN PATENTS Great Britain June 28, 1934 Germany Mar. 19, 1953 Germany July 29, 1954

Claims

1. A DRY SHAVING RAZOR HAVING A CASING SERVING AS A HANDLE; AN ELONGATE CONVEXLY, CIRCULARLY CURVED SHEARHEAD MOUNTED ON ONE END OF SAID CASING AND BEING COMPRISED OF AT LEAST ONE EXTERNAL TRANSVERSELY SLOTTED SHEARCOMB, AND A MOVABLE CUTTING BLADE WITHIN SAID SHEARCOMB, SAID SHEARCOMB HAVING AN UPPER SURFACE HAVING A RADIUS OF CURVATURE OF ABOUT 75 MM., SAID SHEARCOMB BEING COMPRISED OF A MIDDLE PORTION HAVING A LENGTH RANGING BETWEEN ABOUT 30 TO 35 MILLIMETERS AND HAVING APPROXIMATELY 28 TO 32 OF THE TRANSVERSE SLOTS, AND OF TWO END PORTIONS ONE AT EACH END OF SAID MIDDLE PORTION, THE DISTANCE BETWEEN THE OUTER ENDS OF THE SURFACES OF SAID END PORTIONS AND A TANGENTIAL PLANE THROUGH THE CENTER POINT OF THE TOP EDGE SURFACE OF SAID MIDDLE PORTION BEING SUBSTANTIALLY TWICE THE DISTANCE BETWEEN THE SAID TANGENTIAL PLANE AND THE ENDS OF SAID MIDDLE PORTION OF SAID SHEARCOMB, WHEREBY IN SHAVING THE SOFT PARTS OF THE FACE SAID SHEARHEAD MAY BE PRESSED AGAINST SAID PARTS SUFFICIENTLY STRONGLY AS TO PROVIDE SUFFICIENT STRETCHING OF THE SKIN WITH OPENING OF THE PORES TO ATTAIN SATISFACTORY CLOSE SHAVING WITHOUT THE OUTER ENDS OF THE END PORTIONS OF SAID SHEARHEAD COMING IN CONTACT WITH THE FACE.