Cutlery – Razors – Multiple blade
Reexamination Certificate
1999-02-03
2001-07-31
Rachuba, M. (Department: 3724)
Cutlery
Razors
Multiple blade
C030S057000, C030S346570
Reexamination Certificate
active
06266884
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to wet shaving systems of the blade type and more particularly to a shaving system having three or more movable blades positioned within a blade cartridge.
Shavers have long sought a smooth and close shave. In the pursuit to develop the ideal shaving implement, razor blade cartridges have been developed that include three blades. The triple blade configuration gives a closer shave than conventional dual blade configurations because three cutting edges are used rather than two cutting edges. However, the development of a triple blade cartridge raises the issue of proper orientation of the three blades to optimize razor performance.
A triple blade razor includes a minimum of five contact points that must be considered in order to optimize razor performance. Clearly, the cutting edge of each blade must be considered, but also a skin-contacting surface of a cap member and a skin-contacting surface of a guard member must be considered. Ideally, the shaving forces normal to the contacting surfaces are shared by all of the contacting surfaces, thereby distributing the shaving forces and preventing excessive scraping or nicking by one of the blade edges. The amount shaving forces on each edge is determined by the degree of blade exposure given to that blade. Consequently, the degree of “blade exposure” is crucial to optimizing razor performance.
The term “blade exposure” represents a geometrical relationship between the blades and other skin-engaging surfaces of the blade cartridge. The term “blade exposure” means the distance by which the blade edge projects forwardly of a shaving plane. The “shaving plane” is the plane tangent to skin-engaging surfaces, referred to as the guard member and the cap member, which are disposed on both sides of the blades so as to engage the shaving surface before and after engagement by the blade.
Triple blade razors have been developed that are concerned with proper blade exposure, for example, PCT International Publication Number WO 95/09071, published on Apr. 6, 1995, describes a razor blade unit including three blades mounted within a housing. The razor blade unit includes a guard, a cap, and three blades with parallel sharpened edges located between the guard and the cap. The leading blade has an exposure of less than or equal to zero, the trailing blade has an exposure of greater than or equal to zero, and the exposure of the middle blade is not less than the exposure of the leading blade and not greater than the exposure of the trailing blade. The preferred embodiment of the razor blade described in the WO 95/09071 publication has a progressive increase in blade exposure from the leading blade to the trailing blade, thereby reducing drag forces placed on the blade unit as it is moved over the skin of the shaver.
In the aforementioned patent, the first blade is restricted to an exposure of less than or equal to zero. The restriction of the first blade to a negative exposure or an exposure equal to zero significantly reduces the effectiveness of the first blade to give a close shave. The exposure of the first blade as set forth in the WO 95/09071 publication severely limits the ability of the edge of the first blade to contact the skin of the shaver and cut the hair close to the skin. Overall the invention described in the WO 95/09071 publication fails to achieve optimal blade geometry based on the lack of sufficient positive blade exposure.
In addition to the amount of blade exposure of the blades, a second factor in constructing a wet shaving system that provides a smooth and comfortable shave without having annoying cuts and abrasions is the “shaving angle” of the blades in response to shaving forces. The term “shaving angle” is defined as the acute angle between a plane tangent to the cutting edge of the blade and the shaving plane.
Consequently, a need exists for a triple blade cartridge incorporating optimal blade geometry wherein the shaving forces normal to the contacting surfaces is shared by all of the contacting surfaces to provide a close and comfortable shave. Such a blade cartridge should take into account such factors as proper blade exposure, and shaving angle of the blades in response to shaving forces.
SUMMARY OF THE INVENTION
The present invention provides a novel blade cartridge designed to satisfy the aforementioned needs. A novel feature of the present invention is the development of improved triple blade geometry. In order to develop proper triple blade shaving geometry, five contact points or surfaces with the skin must be considered, which includes the edges of each of the three blades, a skin contacting surface on the guard member and a skin contacting surface on the cap member.
In order to optimize comfort and closeness of a shave, the shaving forces normal to the contacting surfaces should be shared by all five contacting surfaces. This is accomplished by orienting each of the five contacting surfaces at an equal distance from a common axis. In an alternate embodiment of the present invention, the blade cartridge includes more than three blades arranged in a similar manner with all of the contacting surfaces oriented at an equal distance from a common axis.
Accordingly, the present invention relates to a blade cartridge including a platform member having a guard member. The guard member is located on the front side of the platform member so as to form a longitudinal slot between the main portion of the platform member and the guard member. The blade cartridge also includes a primary blade that is disposed on the platform member such that the cutting edge of the blade is located rearwardly of the guard member. Preferably, the cutting edge of the primary blade is parallel to the guard member. A first contact surface is located on the guard member near the first blade and a second contact surface is located on the cutting edge of the first blade.
The blade cartridge also includes a spacer that is located on the primary blade. The spacer includes a rear portion that functions to separate the primary blade and a secondary blade.
The blade cartridge further includes a secondary blade that is disposed on the spacer such that the cutting edge of the blade is located rearwardly of the cutting edge of the primary blade. Preferably, the cutting edge of the secondary blade is parallel to the cutting edge of the primary blade. A third contact surface is located on the cutting edge of the second blade.
The blade cartridge also includes a spacer that is located on the secondary blade. The spacer includes a rear portion that functions to separate the secondary blade and a tertiary blade.
The blade cartridge further includes a tertiary blade that is disposed on the spacer such that the cutting edge of the blade is located rearwardly of the cutting edge of the secondary blade. Preferably, the cutting edge of the tertiary blade is parallel to the cutting edge of the secondary blade. A fourth contact surface is located on the cutting edge of the third blade.
The blade cartridge also includes a cap member disposed on the tertiary blade. The cap member secures the members forming the blade cartridge together. A fifth contact surface is located at a tangent point of contact with the cap member. The blade cartridge further includes a lubrication strip on the cap member.
Each blade of the present invention has a fixed end and a free, or cantilevered, end. The free end of each blade functions as a single cantilever forming a “flexing zone” about which the cutting edge of the blade bends in response to an applied force. Each blade is independently movable in response to shaving forces applied to the blade. Specifically, each blade is flexible about the longitudinal axis of the blade within a flexing zone defined by the ratio between the portion of the blade overlying a physical structure and the portion of the blade overlying the opening formed beneath the forward portion of each blade, in combination with the physical characteristics of the blade. If a force exceeding the resilient force
American Safety Razor Company
McDermott & Will & Emery
Rachuba M.
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