U.S. patent number 3,740,841 [Application Number 05/128,077] was granted by the patent office on 1973-06-26 for safety razor embodying blade pressure control.
This patent grant is currently assigned to Philip Morris Incorporated. Invention is credited to Frederick L. Risher.
United States Patent |
3,740,841 |
Risher |
June 26, 1973 |
SAFETY RAZOR EMBODYING BLADE PRESSURE CONTROL
Abstract
The disclosure introduces a new concept in safety razor
construction; that of the floating head. A floating head is herein
defined as a blade support assembly which is mounted for movement
transverse to the path of movement undergone by the pressure guard.
A safety razor utilizing a floating head construction of the type
herein described is insensitive not only to variations in the
application of handle pressure but also to the angle at which the
razor is held relative to the skin. A biased blade support
assembly, comprising the floating head, is mounted for controlled
pivotal movement toward and away from a skin pressure guard
integral with the razor handle whereby a constant blade pressure
will be exerted on the skin irrespective of the pressure exerted on
the handle and pressure guard.
Inventors: |
Risher; Frederick L. (Laurel,
MS) |
Assignee: |
Philip Morris Incorporated (New
York, NY)
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Family
ID: |
26705346 |
Appl.
No.: |
05/128,077 |
Filed: |
March 25, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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29788 |
Apr 20, 1970 |
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Current U.S.
Class: |
30/63; 30/74;
30/57; 30/77; 30/531 |
Current CPC
Class: |
B26B
21/16 (20130101) |
Current International
Class: |
B26B
21/16 (20060101); B26B 21/08 (20060101); B26b
021/14 (); B26b 021/52 () |
Field of
Search: |
;30/32,50,51,57,69,71,74,77,85,87,89 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simpson; Othell M.
Assistant Examiner: Smith; Gary L.
Parent Case Text
The present application is a continuation-in-part of my previous
patent application Serial No. 29,788 filed April 20, 1970, now
abandoned.
Claims
What is claimed is:
1. A safety razor comprising a handle assembly having a main skin
pressure guard fixed thereto, a blade support having a blade
secured therein and an auxiliary skin guard arranged adjacent the
blade cutting edge, said support blade and auxiliary guard being
mounted for floating movement toward and away from said main guard
and including biasing means urging the support and blade toward the
main guard but permitting movement away from the main guard when
the force imposed thereon by pressure of the razor against the skin
exceeds a predetermined amount.
2. A safety razor in accordance with claim 1 in which said
auxiliary guard is arranged to engage said main guard under the
urging of said biasing means.
3. A safety razor in accordance with claim 1 in which said biasing
means comprises an elastic member.
4. A safety razor in accordance with claim 2 in which said elastic
member comprises a spring.
5. A safety razor in accordance with claim 1 in which said biasing
means comprises magnetic means.
6. A safety razor in accordance with claim 1 in which said blade
support includes an outer cap member spaced rearwardly of the blade
cutting edge and adapted in normal shaving operation to contact the
skin.
7. A safety razor in accordance with claim 1 in which said blade
support is pivotally mounted on the handle assembly.
8. A safety razor in accordance with claim 6 in which said biasing
means comprises a coil spring arranged to urge the blade support
toward said main pressure guard.
9. A safety razor in accordance with claim 1 in which said biasing
means has an effective force urging the blade support toward the
main guard in the range of about 50 to 200 grams.
10. A safety razor in accordance with claim 1 in which said blade
support is constructed to enable the ready replacement of blades
therein.
11. A safety razor comprising a handle assembly including a main
skin pressure guard fixed therein having a skin engaging surface, a
blade support assembly pivotally mounted on said handle for
floating movement toward and away from said main pressure guard,
said blade support assembly including a blade and an auxiliary
guard arranged underneath the blade adjacent to but spaced
rearwardly of the blade cutting edge and an outer cap member
overlying the blade and spaced rearwardly thereof, and spring
biasing means for biasing said blade support assembly toward said
main pressure guard for positioning the blade edge in spaced
juxtaposed shaving position relative to said main skin engaging
surface whereby as said main skin engaging surface is further
depressed into the skin said blade support assembly including the
blade cutting edge may move away from said main skin engaging
surface.
Description
BACKGROUND OF THE INVENTION
The original safety razor development afforded a method of
achieving a close shave without the very real danger of serious
injury that had previously attended the use of straight razors.
Although the safety razor has eliminated the possibility of serious
injury, the very knowledge of this fact on the part of the user has
tended to increase the number of minor abrasions and "nicks"
occasioned by its use since one tends to shave with less care and
precision than would be the case were serious injury possible.
Although the evolution of the safety razor and the concomitant
development of improved blade alloys and honing techniques have
contributed greatly to the ease and comfort of shaving, these prior
developments have been primarily concerned with methods of
achieving a more precise blade angle control relative to the guard,
a faster blade interchange and longer blade life. Present day
safety razors show little improvement over the original models
insofar as the provision of a true "nick-proof" construction is
concerned as is readily apparent to any person who uses such a
razor.
The problem is, perhaps, more pronounced in the case of feminine
use where the areas to be shaven are not always readily visible;
however, even the most experienced shaver is not immune to the skin
"nicks" which are caused by hurried or careless shaving. The most
common cause of these minor injuries is the application of
excessive blade pressure. This may occur, for example, in shaving a
particularly sensitive area, such as the neck or underarms, or in
the failure to vary pressure application as the blade moves across
a varying skin contour. A secondary cause of injury is the failure
to maintain razor handle and its rigidly interconnected blade at a
proper angle relative to the skin.
Although the general proposition of mounting a blade in such a
manner that it may undergo relative movement in relation to its
supporting handle has been previously recognized, as in U.S. Pat.
Nos. 1,479,690; 2,059,172 and 2,125,135; in all of these prior
constructions there has been a direct relationship between the
pressure exerted by a user on the razor handle and the blade
pressure against the skin. Thus in U.S. Pat. No. 2,059,172, the
blade edge may undergo limited relative movement parallel to the
axis of the razor handle and may also rotate about a generally
vertical axis. In U.S. Pat. Nos. 1,479,690 and 2,125,135 the blade
edge is pivotally supported to follow the contour of the skin.
Various patents show the blade held to a fixed seat or against
fixed stops by spring means. The above U.S. Pat. No. 2,125,135 is
one such to which may be added the U.S. Pat. Nos. 637,511 and
2,311,913 as embodying that general feature. In each case, however,
the spring is so arranged and of a strength such as to hold firmly
the blade in its fixed shaving position relative to its supports
under normal conditions and is retracted or released only for the
purposes of blade changing. Accordingly in those cases any
excessive pressure application at the razor handle is reflected in
an excessive blade edge pressure. Stated differently, the prior art
as not recognized the advantages in the provision of a safety razor
construction wherein the total blade pressure is due solely to an
independent biasing force and is totally independent of applied
handle pressure.
SUMMARY OF THE INVENTION
The invention resides in the provision of a safety razor having a
blade mounting assembly which is mounted for controlled pivotal
movement toward and away from the normal path of movement undergone
by the pressure guard during a shaving operation. The pressure
guard may be rigidly secured to the razor handle and the total
pressure applied to the skin, by the application of handle
pressure, is through the pressure guard. An independent biasing
force provides the desired blade edge pressure and this force will
be the same whether the pressure guard is under a light or heavy
pressure application from the handle.
In a preferred embodiment, a main pressure guard is rigidly secured
to the handle and occupies the same position relative thereto as
does the pressure guard of a conventional injector type razor. The
blade support assembly is pivotally mounted in overlying
relationship to the main pressure guard for limited movement
between first and second positions respectively adjacent to and
spaced from the pressure guard. Any desired biasing means such as a
coil spring, leaf spring, torsion spring or a mass of resilient
material may be provided to react between the blade mounting
assembly and either of the rigidly related handle or pressure guard
which, together, comprise the handle assembly. Alternatively, a
magnetic biasing force may be used. In any event, the blade holder
assembly is normally biased toward engagement with the main skin
pressure guard at which position the blade edge is closely related
to the skin engaging edge of the pressure guard and in such
relation thereto as to define a conventional blade angle
positionment relative to the pressure guard. As the razor is moved
along the skin and the pressure guard describes its path of travel
along the skin surface, the blade edge is held into contact with
the skin surface solely by the strength of the biasing force. Any
variation in the angle at which the razor is held tending to
produce an improper blade to skin angle or any increase in pressure
applied to the handle beyond the strength of the biasing force is
compensated for by movement of the blade edge, against the biasing
force, away from t e skin in a direction transverse of the path of
movement undergone by the pressure guard. It will thus be apparent
that irrespective of the angle at which the razor is held or the
pressure that is applied thereto, the blade edge pressure against
the skin will never exceed the strength of the biasing force and
will, in effect, float across the skin as though being towed by the
pressure guard which may be pressed against the skin with any
desired force. Normally the floating head will have blade holding
parts including auxiliary guard means that float with the head
which absorb some of the pressure so that the actual pressure on
the blade edge will be a little less than the total biasing
force.
It will, of course, be apparent that it would be possible to hold
the razor at such an angle that the blade holder assembly would
reach its outermost position at which time the same would act very
much like a conventional razor lacking a floating head. To assure
against injury in the unlikely event that the razor should be held
at such an extreme angle, the pivotal relationship of parts is
chosen such that, at its outermost position relative to the main
pressure guard, the angle made by the blade edge with respect to
the skin approaches zero.
The strength of the biasing force is, desirably, adjustable to take
into account individual variables as regards toughness of beard,
skin sensitivity, etc.
DESCRIPTION OF THE DRAWINGS
The achievement of the foregoing and other advantages will become
more apparent from the ensuing description of a number of
modifications when considered in conjunction with the attached
drawings, wherein:
FIG. 1 is a schematic illustration of the concept involved in each
of the following specific embodiments;
FIG. 2 is a perspective view of one embodiment of the invention
wherein the floating head is biased toward the pressure guard by an
adjustably biased compression spring;
FIG. 3 is a sectional elevation taken along line 3--3 of FIG.
2;
FIG. 4 is a side elevational view, with parts broken away, of a
razor similar to that shown in FIG. 2 but wherein the compression
spring is arranged between the pressure guard and blade assembly
and the pivot point is moved forwardly;
FIG. 5 is a side elevational view, with parts broken away, of a
razor constructed in accordance with the invention wherein a leaf
spring is used to provide the adjustable bias;
FIG. 6 is a side elevational view of a razor similar to that of
FIG. 5 but wherein the skin engaging edge of the pressure guard is
resiliently related to the handle;
FIGS. 7 and 8 are side elevational views depicting, respectively,
the use of attractive and repulsive magnetic forces to provide the
desired bias;
FIG. 9 is a side elevational view of a razor which includes further
details of a particular embodiment of the invention;
FIG. 10 is a front view thereof looking in the direction of arrow
X;
FIGS. 11 and 11A are fragmentary views illustrating some of the
geometry and relation of parts involved in a razor such as that of
FIGS. 9 and 10; and
FIG. 12 likewise depicts some of the geometry including the force
factors.
DESCRIPTION OF PREFERRED EMBODIMENTS
In FIG. 1 is schematically illustrated the basic concept herein
disclosed as embodied in a safety razor 10 having a handle 12, a
related member 14 carrying a pressure guard at its outer end and a
floating head or blade support assembly 16. The handle 12 and
pressure guard member 14 comprise the handle assembly. Blade
support assembly 16 includes a conventional blade clamp 18 for
mounting a blade 20 whose lower cutting edge 22 is biased about
pivot axis 24 into the solid line position, defining a proper
shaving angle 26 with respect to skin surface 28, by biasing means
30 which in FIG. 1 is of elastic material with a rigid non-rotary
connection to the razor at point 24. So long as the shaving
pressure applied at handle 12 in the direction of arrow 32 does not
exceed the value of biasing means 30, the blade edge 22 will track,
or follow, the skin engaging edge 31 of pressure guard 14 in the
relative position shown in solid lines and the value of the biasing
means, alone, will determine the blade pressure applied to the
skin. As soon as the handle pressure, such as along arrow 32, is
increased beyond that which may be resisted by biasing means 30,
the blade support assembly and blade edge 22 will move upwardly
either to the phantom line position shown in FIG. 1 or to some
intermediate position dependent upon the degree of handle pressure
application and the depression of the skin surface by the
application of such pressure thereto through the skin engaging edge
of the pressure guard.
Thus, assuming a force of X grams to be applied at blade edge 22 by
biasing means 30 and a force application along arrow 32
insufficient to override the biasing means it will be appreciated
that the parts would maintain the solid line position of FIG. 1 and
the shaving operation would proceed with a force of X grams at the
blade edge. As handle pressure is increased to indent the skin
surface, as indicated in the lower dotted line position 33 of FIG.
1, it will be appreciated that it is only the pressure guard which
is exerting a greater pressure on the skin; the blade support
assembly having pivoted upwardly so that blade edge 22 still exerts
a force of only X grams on the skin surface. Similarly, as the
angle at which handle 12 is varied such as, for example, as to
decrease angle 26, the blade support assembly will pivot upwardly
about axis 24 while, simultaneously, inherently reducing the angle
of attack between blade 20 and the skin surface.
Turning now to a description of FIGS. 2 - 8 portraying exemplary
ones of specific razor constructions embodying the features
conceptually shown in FIG. 1, it will be noted that each employs a
floating head; the primary distinctions being the manner in which
the bias is applied.
A first more specific embodiment of the invention is illustrated in
FIGS. 2 and 3 wherein a plastic handle 112 rigidly supports a skin
pressure guard plate 114 onto the upper surface of which is
pivotally mounted a floating head or blade support assembly 116 for
limited pivotal movement about pivot 124 under the influence of
spring 130 adjustable as to tension by screw 133 threaded into the
boss 135 secured to the guard plate 114. In accordance with common
razor head and blade construction the floating head includes a
bridge member 140 having a platform 141 on which is seated the
blade 120 the blade being secured between the bridge platform and
the overhead clamping plate 145 formed integral with the floating
head main frame member 146. The bridge member is urged into the
angle formed by the frame parts 145, 146 by suitable spring means
common in the injector razor art comprising in the present case a
leaf spring member 142 bearing against a lug 140a integral with the
bridge member 140. The bridge platform 141 has the usual stops 147
with which the blade cutting edge 122 engages. The blade is
replaceable in the manner common in injector type razors through
insertion of a magazine tang into the opening 143 to spring apart
slightly the platform 141 and clamping plate 145 to free the blade.
The bridge member is also provided with an auxiliary blade edge
guard 148 which engages normally with the stationary main guard 149
fixed on the plate 114. Spring 130 normally biases the blade
support assembly to the position shown in FIGS. 2 and 3 wherein the
blade edge guard 148 is bottomed on the upper surface of the main
pressure guard 149. The biasing forces maintaining the relationship
of parts shown in FIG. 3 may be adjusted by rotation of set screw
133.
In FIG. 3 the skin surface is indicated by the line 150 and it will
be noted that as the razor travels over the skin in the direction
indicated by arrow 137 the blade edge guard 148, the blade cutting
edge 122 and the forward edge at least of the cap plate 145 all
engage the skin when the razor is held at an appropriate angle. The
major force tending to rock the floating head reversely about its
pivot 124 is of course the pressure against the blade cutting edge
particularly when cutting hairs. However, forces derived from the
frictional engagement of surfaces 148 and 145 with the skin
contribute to some extent to the total force tending to swing the
floating head on its pivot, the relative forces varying dependent
upon the conditions including the relation of the razor parts.
As a net result in operation as the main pressure guard 149 is
moved along its path of travel over the skin surface, as indicated
by arrow 137, the blade edge 122 will "track" the pressure guard
149 and blade edge guard 148 will remain in contact therewith until
such time as the total force tending to rock the floating head
exceeds the counter force derived from the bias of spring 130 at
which time blade support assembly 116 will move upwardly to
floatingly track the pressure guard while still exerting an
adequate and substantially constant blade edge cutting pressure. As
previously noted the major force tending to rock the head against
the counter force effected by the biasing is normally that applied
to the blade cutting edge. In no case, however, does the force with
which the cutting edge engages the face exceed that determined by
the biasing spring. The matter of preferable forces and relation of
the parts will be discussed more fully hereinafter after describing
further examples of biasing means.
FIGS. 4 to 8 depict different types and arrangements of biasing
means. Each figure is intended to illustrate an injector razor
having a floating head embodying the principles of the present
invention but with the blade holding means shown in simplified
diagrammatic form. The spring biasing means shown in FIG. 4 differs
from that of FIGS. 2 and 3 in that the pivot point 224 is
positioned forwardly of the biasing spring 230 and the same is
non-adjustably positioned between the pressure guard 214 and
floating head 216 to normally bias the parts to the solid line
position.
The razor 310 shown in FIG. 5 employs a leaf spring 330 reacting
between a collar 331 secured to handle 312 and the upper surface of
floating head 316. The position of spring 330 is adjustable, such
as between the solid and dotted line positions shown in FIG. 5, by
finger pressure applied to upstanding tang 333 to thereby adjust
the bias applied to floating head 316 in the direction of pressure
guard 314. Otherwise, the operation of the razor is the same as
that described in connection with FIGS. 2 and 3.
Razor 410, shown in FIG. 6, is substantially identical to that
shown in FIG. 5 with one major exception which is that the skin
engaging edge of pressure guard 414 resiliently, rather than
rigidly, related to the handle 412. This is accomplished by the
utilization of a flexible, rather than a relatively rigid, metallic
member as the pressure guard. The flexibility of pressure guard 414
is, of course, less than the flexibility of leaf spring 430 in any
of its adjusted positions. Stated differently, the deflection which
can be undergone by pressure guard 414 due to its pressure
application against skin surface 428 is always less than that which
can be undergone by blade support assembly 416 whereby the same
floating action of the floating head relative to the pressure guard
is retained.
Razor 510, shown in FIG. 7, relies upon the use of magnetic
attraction to provide the biasing force. Unlike, attractive magnets
530 are mounted, respectively, to the lower surface of floating
head 516 and the upper surface of pressure guard 514 which is
rigidly carried by handle 512. A stop pin 513 limits the opening
movement of assembly 516 relative to the pressure guard. Magnets
530 may be directly opposed, as shown, or offset relative to each
other to provide the desired bias force and it will be seen that as
the application of skin pressure against blade edge 522 exceeds the
magnetic attractive forces, the floating head will move upwardly
against the magnetic bias in a manner analogous to the spring
biased heads.
The razor 610, shown in FIG. 8, differs from that of FIG. 7 in that
like magnets 630 are respectively carried by pressure guard 614 and
floating head 616 through the intermediary of brackets 615 and 617.
In this case, it is the repulsive force of like magnets that is
relied upon to provide the bias toward the solid line
positions.
FIGS. 9 and 10 show another embodiment of the invention in quite
complete form. The main frame assembly includes a handle 712, a
main guard plate 714 fixed therein having a main skin pressure
guard 715. The floating head assembly embodies a main blade
supporting member 716 having a boss portion 717 pivoted at 718
between a pair of spaced lugs 719 turned up from the plate 714. The
blade head is generally similar to that of FIG. 3 and includes an
angular bridge member 720 urged into the angle formed by the cap
member 721 on the member 716 by a leaf spring 722 bearing against a
lug 723 integral with the bridge member 720. The blade 725 is
thereby clamped between the bridge member 720 and the cap portion
721. The blade cutting edge 730 is engaged against stops 731.
Release of the blade in changing is effected in the usual manner by
insertion of the magazine tang into the space 732. The bridge
member carries the auxiliary blade edge guard 734 which is normally
urged into contact with the main stationary guard 715 by the
compression spring 736 which has an end fitted into the end of
adjusting screw 737 threaded through the boss 738 on the member
716. Preferably a stop is associated with the screw 737 to insure
against excessive biasing force on the floating head, the stop
comprising here a shoulder formed by the enlarged portion 738 on
the screw.
Some of the criteria to be considered in a practical embodiment of
the invention will be described in connection with FIGS. 11, 11A
and 12 which show on an enlarged scale certain elements
corresponding to elements of the razor of FIG. 9. As in standard
razors shown in prior art patents the present floating head razor
is designed to have an appropriate shave angle. Referring to FIG.
11 the shave angle A comprises the angle between a plane 750 passed
tangent to the surface of the floating head guard 734 and to the
edge of the cap 721 and a plane 751 passed through the center of
the blade including the cutting edge. This angle A may vary
substantially dependent upon various related conditions but in a
razor such as that of FIGS. 9 and 10 it is preferably in the range
of about 20.degree. to 38.degree..
Another related factor is the blade exposure which (FIG. 11A)
comprises the space B between the plane 753 passed tangent to the
floating head guard 734 and the outer edge of the cap plate 721 and
another plane 754 parallel thereto passed through the cutting edge
730 of the blade. Preferably the geometry and relation of the parts
are such in the case of the floating head razor illustrated in
FIGS. 9 and 10 that the fixed guard 715 is also approximately
tangent to the plane 753 when the parts are at rest. As in the case
of the shave angle the blade exposure B may vary dependent upon the
circumstances and the relation of the various parts but it has been
found that in most cases a blade exposure in the range of about
0.000 to 0.010 of an inch is desirable.
A major factor for satisfactory functioning of the razor is of
course the biasing force which means the shaving pressure at which
the floating head begins to retract. The total force applied to the
razor head during shaving is in a direction generally corresponding
to the line 760 in FIG. 12. This of course has components indicated
by the line 761 extending through the blade and in the general
direction of the razor movement along the skin and a line 762
extending from the blade edge perpendicular to the line 761. The
force tending to rock the floating head rearwardly away from the
skin about its pivot is resisted by the spring biasing which should
not of course be sufficiently high to defeat the purpose, but
within that limitation it can vary considerably dependent upon the
particular design of the razor as a whole including the selected
shave angle and blade exposure. Such variation of course can be
embodied in the spring adjusting means where that feature is
included. In general it has been found for practical purposes that
the biasing means should preferably be of such character and
strength as to require a force at the effective direction indicated
by line 760 in the range of about 50 to 200 grams.
The drawings and the foregoing description illustrate various
applications of the principles of the invention but it will be
apparent that still other adaptations may be made and accordingly
it is intended that all matter contained herein shall be
interpreted as illustrative and not in a limiting sense.
* * * * *