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Darwin Razor

PatentGB243881

InventionImprovements in or relating to Safety Razors

FiledMonday, 3rd November 1924

PublishedThursday, 10th December 1925

InventorPaul Richard Kuehnrich

LanguageEnglish

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A PDF version of the original patent can be found here.

PATENT SPECIFICATION
Application Date : Nov. 3, 1924. No, 26,135/24. Complete Left: May 15, 1925. Complete Accepted: Dec. 10, 1925.

PROVISIONAL SPECIFICATION. Improvements in or relating to Safety Razors.
243,881

I, Paul Richard Kuehnrich, of Holly Court, Ecclesall, in the City of Sheffield, a subject of the King of England, do hereby declare the nature of this invention to be as follows:—

This invention relates to safety razors of the type in which a double edged blade is clamped between a backing and a guard by means of a handle engaging a screwed extension of the backing, its object being to provide improvements in the construction and shape of the backing and guard whereby the razor may be more efficiently clamped and manipulated.

According to the present invention the exposed portion of the backing, instead of being convex in shape as has been the usual practice heretofore is formed with two concave surfaces, each extending from one longitudinal edge and meeting the other in a central ridge parallel to these edges. The inner surface of the backing carrying the clamping extension is preferably also concave, though it may, if desired, be a plane surface in some cases.

The concavity of each of the outer surfaces is preferably that of a cylinder of about 1½ to 2 inches in diameter having its axis parallel to the longitudinal edges of the backing, and that of the inner surface is also cylindrical and similarly disposed. The relative disposition of the outer concave surfaces is such that each forms an approximate continuation of the razor blade, being tangential or approximately so thereto.

The comers of the backing are preferably employed to clamp the blade, the guard being shaped to provide a slight recess between its comb and the blade edges intermediate their ends. The clamping extension is centrally disposed on the hacking and the longitudinal edges of the latter are made thin enough, preferably in conjunction with the concave inner surface of the backing, to develop a spring action, so that when a blade is clamped between the backing and guard these edges will spring or give slightly at the corners which clamp the blade on the guard, and thus produce a nut-lock action on the screw connection between the handle and the clamping extension of the backing.

The guard is preferably formed with a slot through it parallel with and adjacent to each of its combed edges on the inner side of the latter, each of the combs being conveniently provided by an undulating or corrugated formation of the surface between the slots and the longitudinal edges of the guard. The slots are made of sufficient width to allow free passage, for lather and hair when shaving and for water when cleaning, between the blade and comb.

It will be appreciated that by the employment of the present invention not only is the blade efficiently clamped at all four corners in spite of any slight difference in level of the clamping points but the shape and appearance of each side of the razor will be similar to that of a hollow ground razor, the central ridge corresponding to a common back and the renewable blade providing the two cutting edges. In operation the scraping action which is such an objection to most varieties of safety razor may easily be eliminated and a shaving stroke may be obtained with great facility corresponding to that obtained by the skilful manipulation of a hollow ground razor, for the central ridge when in contact with the skin will form a guide determining the correct angle at which the edge of the razor should be presented to the skin. The formation of the guard is such that there will be little or no liability of the blade being clogged when in use, whilst it may easily be cleaned by directing a jet of water from a tap through the slots in the guard.

The backing is provided with pins or projections engaging holes or a slot in the blade and guard to prevent relative rotation of these three parts, and according to another feature of the present invention these pins may be conical or have one or more inclined sides in order that the parts may be automatically adjusted to the correct relative position as the blade is clamped between the backing and guard. For this purpose the bases of the pins are made to fit suitable openings in the blade and guard with an absence of appreciable play when in the assembled clamping position, the free ends of the pins being smaller than these openings to facilitate assembly.

Dated this 1st day of November, 1924.

ARTHUR H. GREENWOOD,

Chartered Patent Agent,

39, Bank Street, Sheffield.



COMPLETE SPECIFICATION. Improvements in or relating to Safety Razors.

I, Paul Richard Kuehnrich, of Holly Court, Ecclesall, in the City of Sheffield, a subject of the King of England, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:—

This invention relates to safety razors of the type in which a double edged blade is clamped between a backing and a guard by means of a handle engaging a screwed extension of the backing, its object being to provide improvements in the construction and shape of the backing and guard whereby the razor may be more efficiently clamped and manipulated.

According to the present invention clamping surfaces are formed at the ends of the guard and are stepped clear of a comb at each longitudinal edge of the guard. A backing is provided bridging the clamping surfaces both longitudinally and transversely and is thereby adapted to clamp the blade at four points on these clamping surfaces.

The clamping surfaces are conveniently plane or concave and the backing may be formed with a concave inner surface (as is known for other purposes) in order to bridge the clamping surfaces transversely, the longitudinal bridging being effected by the clamping surfaces being stepped clear of the comb. The longitudinal edges of the backing are preferably thin enough to develop spring action when its four corners are pressed against the clamping surfaces of the guard, so that these edges will spring or give slightly at the corners which clamp the blade. The exposed portion of the backing is also preferably formed with two concave surfaces each extending from a junction with the inner surface as an approximate continuation of the razor edge to meet the other in a central edge or ridge.

It is usual to provide the backing of razors of the type to which this invention relates with positioning pins having cylindrical bases and conical points, but in practice the base portions have been made smaller than the corresponding holes in the blade to facilitate assembly or to allow the blade to be distorted. The result has been to allow slight relative movement between the blade and guard, so that it has been necessary to adjust the blade by hand when clamping it between the backing and guard. The present invention provides for automatically bringing backing blade and guard into the correct relative positions by making the base portions of the positioning pins accurately to fit the sides of the apertures in the other two members and by providing the pins with inclined faces at their free ends guiding such apertures to the base portions.

In the accompanying drawings :—

Figure 1 is a perspective view of a safety razor according to the present invention,

Figure 2 is a plan of the guard,

Figure 3 is a transverse section through one of the positioning pins,

Figure 4 is an edge view of the guard,

Figure 5 is an underside plan of the razor and Figures 6, 7, 8 and 9 are views similar to Figure 5 illustrating modifications.

Like reference numerals indicate like parts throughout the drawings.

A safety razor according to the present invention comprises a double edged blade 10 which is clamped between a backing 11 and a guard 12 by means of a handle 13 engaging a screwed extension 14 of the backing 11.

The guard 12 is formed with a comb15 at each longitudinal edge and with a slot through it parallel with, and adjacent to, each of its combed edges on the inner side of the latter as shown at 16 in Figure 2. Each of the combs is conveniently provided by an undulating or corrugated formation of the surface between the slots 16 and the longitudinal edges of the guard as indicated in Figures 1, 2, 3 and 4. Clamping surfaces 17 are formed at the ends of the guard 12 and are stepped clear of the combs 15 as clearly shown in Figures 2, 3 and 4. The backing 11 is adapted to bridge the clamping surfaces 17 both longitudinally and transversely so that it is the four corners of the backing which alone are operative to clamp the blade to the surfaces 17. The longitudinal bridging is effected by the clamping surfaces 17 being stepped clear of the combs 15 above which the longitudinal edges of the backing 11 are disposed. The transverse bridging is provided by forming the backing 11 with a longitudinal concave inner surface as shown at 18 in Figure 3. The longitudinal edges of the backing 11 are made thin enough to develop a spring action so that when a blade is clamped between the backing and guard these edges will spring or give slightly at the corners which clamp the blade on the guard and thus produce a nut-lock action on the screw connection between the handle 13 and the clamping extension 14 of the backing. This spring action of the longitudinal edges of the backing is preferably ensured by making the exposed portion of the backing with two concave surfaces 19 and 20 each extending from an edge junction with the inner surface 18 to meet the other in a central ridge as shown in Figures 1 and 3.

The concavity of each of the outer surfaces 19 and 20 is preferably that of a cylinder of about 1½ to 2 inches in diameter having its axis parallel to the longitudinal edges of the backing, and that of the inner surface 18 is also cylindrical and similarly disposed. The relative disposition of the outer concave surfaces 19 and 20 is such that when the razor is assembled each forms an approximate continuation of the blade edge, being tangential or approximately so thereto as shown in Figures 1 and 3.

It will be appreciated that by the employment of the present invention not only is the blade efficiently clamped at all four corners in spite of any slight difference in level of the clamping points but the shape and appearance of each side of the razor will be similar to that of a hollow ground razor, the central ridge corresponding to a common back and the renewable blade providing the two cutting edges. In operation the scraping action which is such an objection to most varieties of safety-razor may easily he eliminated and a shaving stroke may he obtained with great facility corresponding to that obtained by the skilful manipulation of a hollow ground razor, for the central ridge when in contact with the skin will form a guide determining the correct angle at which the edge of the razor should be presented to the skin and this guiding of the razor will greatly assist the desired oblique forward movement of its cutting edge.

The cutting edges of the blade 10 as well as the longitudinal edges of the backing 11 bridge the clamping surfaces 17 longitudinally above the combs 15 leaving a clear space between the blade and comb as shown in Figure 3, the slots 16 are made of sufficient width to allow free passage right through this space between blade and comb for lather and hair when shaving and for water when cleaning. There will thus be little or no liability of the blade being clogged when in use whilst it may be easily cleaned by directing a jet of water from a tap through the slots 16.

The backing 11 is provided with pins or projections 21 engaging holes 22 in the guard 12 and a slot 23 in the blade 10 to prevent relative rotation of these parts in the usual manner. These pins 21 have conical ends or one or more inclined sides at their ends in order that the parts may be automatically adjusted to the correct relative position as the blade is clamped between the backing and guard. For this purpose the base portions 24 of the pins 21 are made accurately to fit the sides (facing the longitudinal edges of the razor) of the apertures 22 and 23 in the guard and blade respectively with an absence of appreciable play when in the assembled clamping position. The free end of each pin 21 is smaller than its base portion which is connected to such free end by one or more inclined faces guiding the apertures 22, 23 to the base portion 24 in order to facilitate assembly. Such inclined faces may be provided by a conical formation of the pins as shown in Figures 3 and 5, by a pyramidal shape as shown in Figure 6 or by a wedge-like shape as shown in Figures 7, 8 and 9, Figure 7 showing each pin with two oppositely disposed inclined faces, Figure 8 with two adjacent inclined faces and Figure 9 with a single inclined face.

If desired the clamping surfaces 17 instead of being plane as illustrated may be slightly concave, or they may be provided by four bosses or other projections situated one at each corner of the guard 12. If desired the clamping surfaces 17 may even be somewhat convex, the transverse bridging being provided by making the concave surface 18 of the backing 11 of greater curvature.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is:—

1. In a safety razor of the type referred to the provision of clamping surfaces at the ends of the guard stepped clear of a comb at each longitudinal edge of the guard, in combination with a backing bridging the clamping surfaces both longitudinally and transversely and adapted to clamp the blade at four points on such clamping surfaces, substantially as described.

2. A safety razor according to Claim 1 in which the backing is formed with a concave inner surface and its longitudinal edges are thin enough to develop spring action when its four corners are pressed against the clamping surfaces of the guard, and the exposed portion of the backing is formed with two concave surfaces each extending from a junction with the inner surface as an approximate continuation of the blade edge, to meet the other in a central ridge, substantially as described.

3. A safety razor according to any of the preceding claims in which the correct relative position of backing, blade and guard is determined by positioning pins on the guard or backing having base portions accurately fitting the sides of apertures in the other two members and inclined faces guiding such apertures to the base portions, substantially as described.

4. The combination and arrangement of parts constituting a safety razor substantially as described and as illustrated with reference to Figures 1, 2, 3, 4 and 5 or modified as illustrated in Figures 6, 7, 8 or 9 of the accompanying drawing.

Dated this 14th day of May, 1925.

ARTHUR H. GREENWOOD,

Chartered Patent Agent,

39, Bank Street, Sheffield.