EP2448725B1

EP2448725B1 - Lower blade assembly for dry shaver

Info

Publication number: EP2448725B1
Application number: EP10734331.1A
Authority: EP
Inventors: Andreas Wurl
Original assignee: Braun GmbH
Current assignee: Braun GmbH
Priority date: 2009-07-03
Filing date: 2010-07-01
Publication date: 2016-08-24
Anticipated expiration: 2030-07-01
Also published as: WO2011001406A1; DE102009031627A1; EP2448725A1

Description

The present invention relates to a lower blade assembly for a dry shaver having an upper blade equipped with openings and a motor for driving the upper blade and lower blade assembly so as to oscillate relatively with respect to one another.
Dry shavers and electric shaving devices for shaving hairs are well known. The clipping head or the clipping unit of a dry shaver typically has an upper blade that makes contact with a section of the skin to be shaved, and said upper blade is typically formed as a clipping foil but also as a comb- or clipping bar-shaped clipping element (hair trimmer), each having distributed passage openings for hair. A translationally oscillating lower blade or a lower blade assembly having multiple cutting blades is arranged underneath the upper blade, opposite the upper blade. Due to the relative movement of the upper blade and lower blade with respect to one another, hairs, which penetrate into the openings of the upper blade and are grasped by the lower blade underneath, are pressed against the edge, which is up against the opening of the upper blade, and are either clipped off upon further movement of the lower blade in relation to the upper blade or are cut correspondingly with a suitably sharp-edged design of the lower blade and/or upper blade.
The design of the lower blades with a steep-angled, sharpened cutting edge, which lies at the front or is leading in the movement direction, basically provides for a satisfactory shaving result. However, a lower blade equipped with a sharpened cutting edge can cause skin irritations, particularly when not just the hair to be cut but also a section of skin surrounding the hair protrudes into the opening of the upper blade and goes into to the cutting plane between the upper blade and lower blade.
Furthermore, known in the prior art are shaving systems that are designed to pull out the hair to be cut, along with its root, a certain length from the section of skin before the actual cut and to separate said hair, while in the pulled-out condition, as close to the skin surface as possible, so that after the cut is complete, the hair root goes back and the hair tip comes to rest under the surface of the skin.
Implementation of a pulling mechanism as such that acts on the hair is quite complex with the dry shaver clipping heads that operate in a translationally oscillating manner, because a corresponding function part, which functions as the pulling element, is placed upstream of the lower blade, in both movement directions of the oscillatory movement.
Furthermore, a protector element with an external contour that is rounded off and facing toward the upper blade can be placed upstream of a cutting edge of a lower blade, in the movement direction. Such a protector element can be transferred into a position that is set back with respect to the cutting plane between the upper blade and the lower blade. It causes at least a section-by-section push-back, of the sections of skin reaching into the cutting plane before they are grasped by the lower blade, provided for actually cutting the hair, and, under such circumstances, injured.
Consequently, the implementation of a protective mechanism for the skin by means of upstream protector elements or even implementation of a pulling function by means of pulling elements upstream of the lower blade, each in the movement direction, require an at least three-component functional unit comprising a lower blade provided for shortening or cutting the hair and two functional parts allocated to the lower blade, either two protector elements or two pulling elements. As a result, realization of a skin protection function and/or a pulling function is associated with a significant increase in the number of functional parts of a lower blade assembly.
Such a configuration is shown, for example, in Figure 4. The actual lower blade 1 provided for separating the hairs, which has steep-angled cutting edges with a cutting edge angle of significantly less than 90° for the purposes of reducing the cutting forces, is arranged between two protector elements 2, 3 or pulling elements 2, 3. An entire lower blade assembly has up to 30 or more lower blades 1, whereby a number of up to 60 or more functional parts 2, 3 results, which are allocated to the respective lower blade 1, and said functional parts can be formed, depending on the design, as protector elements or as pulling elements. All in all, such a lower blade assembly would comprise up to 90 or more individual functional parts.
The arrangement of such a large number of components is not only relatively complex with respect to their design and assembly; also of consideration is that the front surface, facing above, of all of the functional parts 2, 3 glides along the underside of an allocated upper blade in a frictional manner. Thus, a three-component functional unit 1, 2, 3 has increased friction as compared to a single lower blade 1 provided for cutting or trimming hairs and requires a correspondingly high amount of drive power. However, this complexity can be reduced in that the two functional parts 2, 3 are combined in one component, as is shown in assembly 4 located to the right in Figure 4.
In addition, it must also be considered that certain minimum component sizes must be maintained due to a limited selection of material and due to specific mechanical load requirements, which means that the number of functional units of a lower blade assembly may have to be reduced significantly to realize a three-component functional unit. However, a reduction in the number of functional units of a lower blade assembly negatively influences the shaving result and shaving comfort. A dry shaver according to the preamble portion of claim 1 is known from EP-A1-0 086 536 and WO-A1-2005/046947 .
Thus, the object of the present invention was to provide an improved lower blade assembly for a dry shaver, which would have, as a whole, a reduced number of functional parts per functional unit and which would be relatively simple to assemble and economical to produce and, in addition, which would lead to good or even improved shaving results with an increase in shaving comfort for the user.
The object upon which the invention is based is achieved by means of a dry shaving device according to claim 1. Advantageous embodiments of the invention are indicated in the dependent claims.
The lower blade assembly according to the invention is intended for a drive shaver, which has an upper blade having openings and a motor, wherein the motor is provided for driving the upper blade and lower blade assembly so as to oscillate relatively with respect to one another. The relative movement, which is driven in an oscillatory manner by the motor, is translational between the lower blade assembly and the upper blade. For example, the lower blade assembly oscillates back and forth, while the upper blade is arranged in a fixed manner in relation to the housing of the dry shaver.
The lower blade assembly has at least a first and a second lower blade, wherein the one blade, which trails a blade that is leading in the movement direction, is provided for separating, clipping, or cutting a hair protruding into or going through the opening of the upper blade. A particular provision with this is that the two lower blades, the first and the second, alternate from one another with respect to their function depending on the movement direction. For example, if the first lower blade is ahead of the second lower blade in a first movement direction, only the second lower blade is intended for separating the hair. On the other hand, when the movement direction reverses, in which the second lower blade is ahead of the first lower blade, only the second lower blade is intended and designed for separating a hair.
The function of the two lower blades of a functional unit thus varies with each reversal of direction of the oscillatory movement of the lower blade assembly and the upper blade. The function of the first and second lower blade thus adaptively match the respective movement direction.
Within the scope of the invention, a particular provision is that a functional unit of the lower blade assembly now only has two functional parts, namely a first and a second lower blade, instead of three functional parts, or that it consists only of a first and a second lower blade.
Due to the functional adaptation of the first and second lower blade to a requirements profile specified by the respectively predominant movement direction, the total number of necessary functional parts can be reduced in an advantageous manner. As an alternative or supplement to this, there can be a provision to increase the total number of functional units having a first and second lower blade, so that the entire lower blade assembly can have up to 30 or more individual functional units, each comprising a first and a second lower blade.
Thus, on one hand, the production costs and the assembly complexity can be kept in check and, on the other hand, a good shaving result as well as satisfactory shaving comfort can be provided.
The respective lower blade of a functional unit, which is leading in the movement direction, can either be used as a protector element to protect the skin or as a pulling element to pull the hair out from the skin; while the respective blade which is trailing the movement direction is provided for separating or cutting the hair that is protruding into or through the opening of the upper blade.
According to a first preferred embodiment of the invention, a provision is that the first lower blade, which is ahead in a first movement direction of the lower blade assembly relative to the upper blade, is provided for exerting a tensile force on a first hair and the second blade, which is trailing the first blade, is provided and designed for separating said hair. However, in a second movement direction, which is opposite the first movement direction, the second blade, which may have previously separated off a hair, is designed for exerting a tensile force on another hair, for example a second hair, wherein the first blade is then intended to separate off this second hair. Thus, the functionality of the first and second lower blade alternates with each reversal of movement in the course of the oscillatory movement between the lower blade assembly and the upper blade.
Instead of a pulling effect, the leading lower blade can also function as a so-called protector element, which effects a pushing back of sections of skin protruding into or through the opening of the upper blade. In this process, a particular provision can be made that the leading blade be subjected to spring pretension as long as a pushing-back effect is being exerted on the section of skin, until the protector element reaches the contact position, for example, as a result of a resistance that becomes greater due to the clamping of a hair with a chamfer adjoining the cutting edge of the trailing blade, and hereby is placed into a position that is lowered or set back with respect to the cutting plane.
With an embodiment of the leading lower blade as a pulling element or as a pulling blade, a possible provision is that the corresponding blade hooks into a hair, thereby exerting a tensile force on said hair due to a quasi positive-locking connection with the hair. As an alternative or supplement to this, it can be provided that the leading lower blade be subject to a spring pretension of suitable dimension that would enable the leading lower blade to execute a yielding movement upon making contact with a hair, such that a hair protruding through the opening of the upper blade would be bent by the leading lower blade and clamped between the upper side of the lower blade and the lower side of the upper blade, wherein, due to the available adhesive and sliding friction between the upper side of the lower blade and the lower side of the upper blade, a corresponding pulling effect could be exerted on the respective hair.
According to another embodiment of the invention, it is provided that the respective cutting edge or edge, which is at the front in the movement direction, of the blade that is trailing in the movement direction be provided and designed for separating off or cutting the hair or multiple hairs protruding through the opening or into the opening of the upper blade. In doing so, there can be a special provision that said cutting edge be designed as a sharpened cutting blade with an edge radius in the micrometer range, so that a cleaner and smoother cut of a hair can be carried out during shaving, which is considered to be especially pleasant by users.
According to another preferred embodiment, it is provided that the lower blade that is leading in the respective movement direction be subject to a spring pretension that is less than that of the trailing lower blade. The spring pretension, which preferably both the lower blades, the leading as well as the trailing lower blade, are subject to is directed toward the upper blade. The spring pretension is thus essentially aligned vertically with respect to the oscillating movement direction of the two lower blades.
Due to the fact that the leading or upstream lower blade is subject to a spring pretension that is less than that for the trailing blade, the leading blade can provide a protective function for the skin or a pulling function on the hair to be shortened, while the trailing blade, which is subject to a higher spring pretension, is designed to separate off a hair that is clamped between the trailing blade and an opening edge of the upper blade.
In doing so, a particular feature is that the spring pretension directed toward the upper blade can be changed upon a reversal of movement of the two blades. In particular, it is provided that the spring pretension of the first and of the second lower blade, be exchangeable along with a reversal of movement, within the scope of the oscillating movement of the entire lower blade assembly, because the lower blade can reverse its function when an opposite drive movement is put into place.
To this end, there can be a provision, for example, that the spring element support points, which are facing away from the first and second lower blade, assume the required position for providing the required spring pretension, depending on the predominant oscillation movement direction. Thus, for example, a provision can be that the pretension force of the first spring or its housing-side pivot point is arranged somewhat further away from the upper blade or from the cutting plane between the upper blade in the lower blade assembly than is the case with the opposite movement. Thus, a particular provision can be that a movement of the support points or the counter-support points of the spring elements be coupled with the respective movement direction of the lower blade assembly relative with respect to the upper blade.
According to a further embodiment of the invention, a provision can be that the first and the second lower blade have an essentially identical exterior contour in an area adjacent to the upper blade. In doing so, the blades could have a symmetrical, somewhat rectangular contour with sharpened but also relatively blunt cutting edges when viewed in the oscillation movement direction, wherein the former is designed for cutting hairs and the latter is designed for clipping hairs, in conjunction with an edge of the upper blade.
A particular provision can be that the blades are designed to be mirror images with respect to an imaginary line of symmetry that proceeds vertically with respect to the movement direction and/or are aligned as mirror images for this purpose. Such type of mirror-image design or alignment of the first and second lower blades arranged in pairs is advantageous with respect to a mass production process, because the first and the second lower blades can be produced identically and one blade must only be rotated 180° with respect to the other within the lower blade assembly.
According to another advantageous embodiment of the invention, a provision is that the edge of the first blade is designed to be relatively blunt at its edge facing toward the upper blade and away from the second blade or to have a rounded-off cutting edge, and has, on the opposite side, a sharpened cutting blade on its edge facing toward the upper blade and toward the second blade.
By means of such an embodiment, the required functionality can be provided to the first and the second lower blade in a particularly simple manner, also without supplying different spring pretension levels.
Because, in this case, it is intended that the relatively blunt or rounded-off edge of a functional unit comprising a first and second lower blade be leading in the movement direction, of the sharpened edge, which lies at the front, of the trailing blade. When the movement reverses, the correspondingly rounded-off or blunt edge of the blade that was previously trailing then lies at the front of the movement direction, while the previously leading blade is then a trailing blade with a sharpened edge lying at the front for cutting the hair.
When considering a functional unit comprising a first and second lower blade, each having edges with differing sharpness levels, the sharpened cutting blades or edges are located at the edges, which are to be aligned toward one another, of the first and the second lower blade, while the rounded-off edges each come to rest outside of the adjacent blade facing away. In this manner, a leading, blunt edge and a trailing, sharpened edge can make effective connection with the hairs or with a section of skin in any movement direction in order to exert a pulling function on the hair or a pushing-away protective function to a section of skin.
In this respect, there is a provision that the second blade have an external contour corresponding to the first blade with its sharpened cutting blade or edge facing toward the correspondingly sharpened cutting blade or edge of the first blade.
According to another embodiment of the invention, a provision is that multiple first and multiple seconds blades are provided, which are arranged to alternate in the movement direction, and all of the first blades are arranged on a first carrier (38) and all of the second blades are arranged on a second carrier (48). The first and the second carrier in this case can be driven in an oscillating manner with respect to the upper blade and are subject to spring pretension with respect to the upper blade. To this end, one or more spring elements are provided for each of the carriers, which can be used to support the carriers at one or at various base parts. The first and the second carrier move synchronously, i.e. the distance between them remains constant in the oscillation direction.
With such type of arrangements, a particular provision is that the blades or cutting blades of the first and of the second carrier are arranged to alternate in the movement direction and that the carriers are arranged to overlap with one another. In doing so, a provision can be, for example, to form the carrier and the blades or cutting blades to be placed thereon from one piece of sheet metal, so that the blades or the cutting blades and the carrier are integrally joined with one another by bonded material or as a single piece.
The spring pretension acting on the carrier or carriers can be formed in different strengths for each carrier and/or can vary over time during operation. However, it is also conceivable for a comparable spring force of about the same strength to be exerted on both carriers, provided the lower blades or cutting blades arranged thereon have edges of different sharpness levels.
According to another independent aspect, the invention relates to a dry shaver with an upper blade equipped with openings and a previously described lower blade assembly, which oscillates by means of a motor, and preferably can be driven to oscillate translationally with respect to the upper blade.
Other targets, features, as well as advantageous application options of the present invention are explained by means of the following exemplary embodiments, with reference to the figures. In doing so, all described features, as well as those shown in figures, represent the subject matter of the present invention, either alone or in any logical combination with one another, including independently of the claims and their references.
The following is shown:

Figure 1: is a schematic representation of two identically designed lower blades of one functional unit;
Figure 2: is another embodiment of two lower blades, which are arranged symmetrically with respect to one another and also asymmetrically;
Figure 3: is a schematic representation of multiple first and second lower blades each arranged on a common carrier;
Figure 4: is a schematic representation of a lower blade functional unit with a total of three functional parts.

Figure 1 shows a very simplified schematic representation of two lower blades, a first lower blade 10 and a second lower blade 20, of a lower blade functional unit. As indicated by the double arrow 14, the two lower blades 10, 20 can be driven in an oscillating and translational manner in the horizontal direction on a drive, which is not explicitly shown, with respect to an upper blade 5, which is also only shown schematically. Each of the lower blades 10, 20 is pretensioned by means of a spring element 12,22, which is provided particularly for this purpose, against the upper blade 5, which is above the two lower blades 10, 20 and is equipped with a perforation and/or with individual passage openings 6. The upper blade 5 can be designed as a clipping foil or also as a comb-shaped or bar-shaped clipping part.
The two lower blades 10, 20 have edges on their top sections, each of which is intended to cut or clip off hairs, so that a hair threaded into an opening 6 of the upper blade 5 lying above is grasped by the lower blades 10, 20 when they move, pressed against an edge 7 of the opening 6 of the upper blade 5, and clipped off or cut off as the movement continues.
In the embodiment shown according to Figure 1, a particular provision is that the pretension force provided by the spring elements 12, 22 be coupled with the movement direction. For example, if the two lower blades 10, 20 move toward the right, what occurs is that the pretension force provided by spring 22 is less than the pretension force of spring element 12. In this manner, the leading lower blade 20 can exert a function that is protective to the skin or that pulls on a threaded-in hair, while the trailing lower blade 10 is impacted with a higher spring force, thus having a higher resistance against descending or recoiling with respect to the upper blade 5, and thus is designed for complete separation of a threaded-in hair.
As soon as the movement direction changes at an apex of the movement, i.e. as soon as the two lower blades 10,20 are moved, for example, to the left with respect to the upper blade 5, the spring force provided by the spring elements 12, 22 also changes. In doing so, a particular provision is that the pretension force acting on the leading lower blade 10 be less than the pretension force that is acting on the trailing lower blade 20. Upon a reversal of movement of the lower blades 10, 20, which can be driven in an oscillating manner, their pretension changes with respect to the upper blade 5.
The respective blade 10, 20 that is leading in the movement direction can be designed as a so-called pulling blade to pull out a hair from a section of skin or as a so-called protector element to push back a section of skin that is protruding into the cutting plane of the upper blade 5 and the lower blade 10, 20. Due to the lower pretension force, the respective leading blade 10, 20 can be placed in a position that is set back with respect to the cutting plane.
A particular provision is that the spring pretension force is to be selected such that the leading blade does not clip off a threaded-in hair but rather clamps the hair, in a recoil behavior with respect to the cutting plane, while forming a gap, which is as wide as the hair, between the upper blade 5 and the leading blade, 10 or 20, wherein, in particular, the external contour, which faces toward the upper blade 5, of the lower blade, has an adhesive or gliding friction with respect to the clamped hair such that said hair is subject to a certain carrying movement and is thus pulled out from the section of skin by the desired dimension, before the hair is separated, under a higher pretension, by the trailing blade, which is essentially not recoiling or only barely recoiling when contact is made with a hair. The carrying of a hair can also occur through hooking with one of the lower blades 10, 20.
An alternative provision can be that the leading blade 10, 20, which lies at the front in the movement direction, have a relatively rounded-off edge, which is not so much designed to hook in a hair but rather is provided to push a section of skin which has protruded into the cutting plane back out of the cutting plane, so that the section of skin is not grasped by a sharpened edge of the leading blade and possibly injured.
Figure 2 shows a further embodiment of a lower blade functional unit having two lower blades 30, 40, each of which is subject to pretension with respect to an upper blade 5, by means of allocated spring elements 32, 42. In doing so, the pretension provided by the spring elements 32, 42 can be changed according to whether the movement direction is toward the right or toward the left. Due to the geometric design of the lower blades 30, 40 however, this is not a mandatory requirement.
Thus, a provision may be that the spring elements 32, 42 essentially have an identical spring constant and thus provide identical spring pretension. The sections of the two blades 30, 40 facing toward the upper blade 5 have external edges 34, 44, which are relatively rounded-off, while the upper edges 36, 46, which face toward one another, of the two lower blades 30, 40 are designed as sharpened cutting blades, each of which has a steep-angled cutting edge.
The sharpened cutting edge or cutting blade 36, 46, which has a cutting angle of significantly less than 90°, is provided for separating and cutting a threaded-in hair, while the rounded-off edge 34, 44 of the other respective blade is provided for pulling out a hair or pushing back a section of skin. If the two lower blades 30, 40 move to the right for example, the rounded-off edge 44 of the lower blade 40 is intended to pull out the hair or to push back a section of skin, while the cutting edge 36 of the trailing blade 30 is designed for cutting the threaded-in hair.
If the movement direction changes toward the left for example, the rounded-off edge 34 of the then leading lower blade 30 then takes on the function of pushing back the section of skin or pulling the threaded-in hair, while the sharpened cutting edge 46 of the trailing blade 40 is intended to completely separate off the threaded-in hair.
Essentially, this is to be realized with identically designed spring elements 32, 42 in the embodiment shown in Figure 2. However, it can also be carried out with a mechanism described in Figure 1, wherein the spring pretension acting on the individual lower blades changes, in the specified manner, as the movement direction reverses.
Finally, Figure 3 shows the coupling of multiple first lower blades 30 on a common carrier 38 as well as the coupling of multiple second blades 40 on a common carrier 48. The individual lower blades 40 are connected with one another in a rigid manner via the carrier 48. The same holds true for the lower blades 30 with respect to the carrier 38. A further provision is that each individual lower blade 30, 40 is no longer impacted with the spring, but that rather that the carriers 48, 38 are supported against a common base 100 by means of spring tension using spring elements 49, 39 intended for this purpose, which can be arranged in the area of the clipping head of the dry shaver.
This design is particularly advantageous with respect to production and assembly of a multitude of individual lower blades. Thus, for example, up to 30 or more lower blades 30, 40 can be arranged on one allocated carrier 38, 48. In doing so, a particular provision is that all first lower blades 30 as well as all second lower blades 40 are produced from one piece of sheet metal.

Reference list

1: Lower blade
2: Pulling blade/protector element
3: Pulling blade/protector element
4: Assembly
5: Upper blade
6: Passage opening
7: Edge
10: Lower blade
12: Spring element
14: Oscillation movement direction
20: Lower blade
22: Spring element
30: Lower blade
32: Spring element
34: Rounded-off edge
36: Sharp edge
38: Carrier
39: Spring element
40: Lower blade
42: Spring element
44: Rounded-off edge
46: Sharp edge
48: Carrier
49: Spring element
100: Base

Claims

A dry shaver having an upper blade equipped with openings, a lower blade assembly and a motor for driving the upper blade (5) and the lower blade assembly so as to oscillate with respect to one another, wherein the lower blade assembly has at least a first (10, 20; 30, 40) and a second (20, 10; 40, 30) lower blade, wherein the one blade (20, 10; 40, 30), which trails a blade that is leading (10, 20; 30, 40) in the movement direction, is provided for separating a hair protruding into the opening (6) of the upper blade (5) characterized in that multiple first (30) and multiple second (40) blades, each of which are arranged to alternate in the movement direction, are provided; all first blades (30) are arranged on one first carrier (38) and all second blades (40) are arranged on the second carrier (48) and in that the first and second carriers (38, 40) are subject to spring pretension with respect to the top blade and/or with respect to a base part (100).
The dry shaver according to Claim 1, wherein, in a first movement direction of the lower blade assembly relative with respect to the upper blade (5), the leading first lower blade (10; 30) is provided for exerting a tensile force on a first hair or for pushing back a section of skin and the second trailing blade (20; 40) is designed for separating the first hair, and wherein, in a second movement direction, which is opposite the first movement direction, the second blade (20; 40) is designed for exerting a tensile force on a second hair or for pushing back a section of skin and the first blade (10; 30) is provided for separating the second hair.
The dry shaver according to any of the preceding claims, wherein the respective cutting edge or edge (30, 40), which is at the front in the movement direction, of a trailing blade (30, 40) is provided for separating or cutting a threaded-in hair.
The dry shaver according to any of the preceding claims, wherein the respective blade that is leading (10, 20; 30, 40) in the movement direction is subject to a lower spring pretension directed towards the upper blade (5) than the trailing blade (20, 10; 40, 30).
The dry shaver according to Claim 4, wherein the spring pretension directed toward the upper blade (5) of each blade (10, 20; 30, 40) is changed with each reversal of movement of the two blades (10, 20; 30, 40).
The dry shaver according to any of the preceding claims, wherein the first and the second lower blade (10, 20; 30, 40) have an essentially identical external contour in an area adjacent to the upper blade (5).
The dry shaver according to any of the preceding claims, wherein the blades (10, 20; 30, 40) are designed to be mirror images with respect to an imaginary line of symmetry that proceeds vertically with respect to the movement direction (14) and/or are aligned as mirror images for this purpose.
The dry shaver according to any of the preceding claims, wherein the first blade (30) is designed to be rounded off or blunt on its edge (34) facing toward the upper blade (5) and away from the second blade (40), and has, on the opposite side, a sharpened cutting blade (36) facing toward the second blade (40).
The dry shaver according to any of the preceding claims, wherein the second blade (40) has an external contour corresponding to the first blade (30) and its sharpened cutting blade (46) is facing toward the sharpened cutting blade (36) of the first blade (30).