Note: Descriptions are shown in the official language in which they were submitted.
1046774
This invention relates to knife blade sharpeners,
and is particularly concerned wi-th such sharpeners as
embodied in a scabbard or protective sheath for a knife
blade. Such sharpener-scabbard combinations form the
subject of Australian Patents 424,122 and 447,537.
Combinations of the above kind include means
whereby a force is maintained between the sharpening
mechanism and a knife blade inserted into the scabbard
and engaging the sharpening mechanism. That force may
be achieved by a biasing spring acting directly or indirectly
on the blade and/or the actual sharpening mechanism. With
these mechanisms, it has been found difficult to arrange
the various reaction zones so that a smooth sharpening
operation can be achieved.
It is a principal object of the present invention
to provide a scabbard-sharpener combination of the kind
indicated in which the aforementioned difficulty is
alleviated or overcome. It is a further object of the
invention in a preferred form, to provide such a com-
bination which is adapted to form a substantially con-
stant cutting angle on a knife blade.
With regard to the last mentione~ object, in
using combinations of the kind indicated, it is necessary
to ensure that the blade is maintained in contact with
the actual sharpening device throughout the sharpening
movement, and that the disposition of the blade relative to
the sharpening device is such that the cutting angle of
the blade is substantially constant throughout the blade
length. The construction disclosed in Australian Patent M7~537
satisfies the first requirement to some extent, but not the
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second. The primary difficulty is that a person operating the sharpener,
can rock the knife blade relative to the sharpening device as that blade is
moved across the sharpening device, and thereby cause alteration in the
cutting angle of the blade.
The cutting angle of the blade is the angle subtended by the
angularly disposed faces of the blade which define the cutting edge. Obvious-
ly, the relative disposition of those faces, and consequently the cutting
angle, is dependent on the form of the sharpening recess provided by the
sharpening device, and the disposition of the lower edge of the blade
relative to the general plane of that recess. If that relative disposition
alt0rs during sharpening, so will the resulting cutting angle of the blade,
and such alteration frequently occurs in the prior constructions because
of insufficient care on the part of the user.
The present invention provides a ~nife sharpener including; a
main body, a carrier member pivotally mounted on said main body, a sharpening
device attached to a front portion of said pivot member at a position forward
of the axis of said pivot mounting and so as to be exposed to an upper side
of said c~rrier member; a reaction member pivotally mounted on said main body
so as to overlie at least part of said carrier member upper side and having
front and rear reaction zones located forwardly and rearwardly respectively
of said carrier member pivot axis and each being arranged in opposed relation-
ship to said upper side, and the axis of said reaction member pivot being
substantially parallel to said carrier member pivot axis and being located
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rearwardly of said rear reaction zone; and biasing means urging the two said
members about their respective pivots so as to resist separation of said
front portion and said front reaction zone.
In a preferred arrangement, the front reaction zone is operative
. to engage the top edge of a knife blade inserted between the carrier and
reaction members and engaging the sharpening device, and the rear reaction
zone is operative to engage thellupper side of the carrier member during at
least an initial part of each sharpening operation. It is necessary however,
that the aforementioned initial part is such that the knife blade extends
to some degree rearward of the sharpening device. That is, when the knife
blade has only limited penetration beyond the sharpening device, the rear
reaction zone engages the upper side of the carrier member, but as that
penetration is extended a stage may be reached at which the rear reaction
zone separates from that upper side. It is also preferred that in the
condition last described, the cutting edge of the knife blade engages a
rubbing surface provided on the carrier member rearwardly of the carrier
member pivot, so that the carrier member is maintained relatively stable
about its pivot, but can rock about that pivot to suit the particular dis-
position of the knife blade.
The knife sharpener preferably includes a guide section pivotally
connected to said main body for movement between an operative position and
an inoperative position, said guide section
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having a slot therein for receiving a kni-Ee blade and
aligning that blade for engagement with said sharpening
device when said guide section is in said operative pos-
ition, and said guide section also functions as a cover
for said cavity when in said operative position, whereby
movement of said guide section in to said inoperative
position exposes said sharpening device for servicing.
With the last mentioned aspect, servicing (e.g.,
cleaning~ maintaining or replacing) of the sharpening device
is facilitated by provision of the pivoted cover~ and
operation of the device is not impaired as that cover doubles
as a guide for the knife blade during sharpening operations.
Such a sharpener arrangement is especially useful in an
assembly involving a reaction member as described above~
particularly when installed in a scabbard housing, but
that is not the only possible application of the sharpener.
Quite obviously, a sharpener as described can be used extern-
ally of a scabbard and without a cooperating reaction
member.
The essential features of the invention, and further
optional features, are described in detail in the following
passages of the specification which refer to the accompanying
drawings. The drawings however~ are merely illustrative
of how the invention might be put into effect, so that
the specific form and arrangement of the features (whether
they be essential or optional features) shows is not
to be understood as limiting on the invention.
In the drawings:
Figure 1 is a plan view of an example embodiment
of the invention.
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Figure 2 is a longitudinal cross-sectional view
taken along line II-II of figure 1.
Figure 3 is a view similar to figure 2 but
showing a knife inserted into the scabbard.
Figure 5 is a cross-sectional view taken along
line IV-IV of figure 1.
Figure 5 is a view similar to figure 4 but showing
a knife blade engaging the sharpening device.
Figure 6 is a cross-sectional view taken along
line VI-VI of figure 5.
Figure 7 is a cross-sectional view taken along
line VII-VII of figure 5.
Figure 8 is a plan view of the carrier member
shown in the preceding views.
Figure 9 is a cross-sectional view taken along
line IX-IX of figure 8.
Figures 10 to 12 are transverse cross-sectional views
taken along lines X-X, XI-XI and XII-XII respectively
of figure 9.
Figure 13 shows part only of the carrier member
of figure 9, with the guide section moved into an
inoperative position.
Figures 14 to 18 are diagrammatic views showing
the various reactions and lines of force at different
stages of a single sharpening operation using the construc-
tion shown in the preceding figures.
A sharpener according to a preferred application
of the invention as shown in the drawings, includes the
basic components of the construction as disclosed by
Australian Patent ~7,537. That is, it includes a hollow
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housing 2 defining a knife receiving passage 3 (figures 2
and 3), a carrier member 4 pivotally mounted in the
housing 2 and supporting a sharpening device 5 (figures 5
and 6)~ an~ a reaction member 6 adapted to coact with a
knife blade 7 (figures 3, 5 and 6) inserted into the
housing 2. In such constructions, biasing means is
required to create pressure between the sharpening device
5 and the knife blade 7 so that effective sharpening
results, and in the constructions prior to the
present invention, that biasing means usually took
the form of a spring which acts between the housing 2
and the knife blade 7~ or a component of the sharpener
such as the carrier 4.
In the sharpener according to the invention, the
carrier ~ is mounted for rocking movement so as to adapt
to positions of an engaging knife blade, and the reaction
member 6 is also pivotally mounted on the housing 2 and
is arranged to engage the carrier 4 and a knife blade 7
in such a way as to achieve a relatively smooth sharpening
action. It is a further feature of the invention, in
a preferred form, that the biasing means acts between two
relatively movable parts of the sharpener assembly so
that it is difficult for the knife blade 7 tobe moved
clear of the sharpening device during a sharpening operation.
Relative terms such as "upper"~ "lower", "front"
and "rear" will be used throughout this specification in
describing an embodiment of the invention. Such terms
are used for convenience only~ and are not to be understood
as placing a limitation on the way in which the sharpener
is to be disposed when in use.
SM 7.
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The housing 2 may be generally as described in
Australian Patent 447,537. In particular, the knife
receiving passage 3 is defined between opposed side walls
8, a top wall 9, and abase 10 of the housing 2, and an
access opening 11 is provided at a front end 12 of the
housing 2. The carrier ~ is preferably an elongated member
which is located in the knife receiving passage 3 so
as to extend generally lengthwise of that passage, and
is pivotally connected to the housing at a location
inwardly of the access opening 11. In the particular
construction shown, that the pivot connection (hereinafter
described) is located intermediate the ends of the carrier~
and is arranged so that the carrier 4 is capable of release
from that connection to permit withdrawal of the carrier
4 through the access opening 11 and out of the housing 2.
The preferred carrier pivot arrangement is best
shown in figures 3, 5 and 7~ and comprises two cylindrical
axle sections 13 which project inwardly from respective
side walls 8 of the housing 2 and which locate within a
recess 14 formed in the adjacent side of the carrier 4.
The upper surface 15 of each recess 14 defines a bearing
surface, which may be arcuate or flat as shown, and the
associated axle section 13 is maintained in engagement
with the surface 15 by resilient retention means, although
other means could be employed for that purpose. According
to the arrangement shown, the resilient retention means
comprises a leaf spring 16 formed integral with the body
of the carrier 4 and adapted to engage beneath each axle
section 13. A separate leaf spring 16 is preferably
provided for each axle section 13 so that a space exists
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~etween the springs 1~ for passage of a knife blade 7,
but in some circumstances a single spring 16 can act on
both axle sections 13. Also, the or each spring 16 could
be attached to the body o~ the carrier 4 rather than being
formed integral therewith. The upper surface 17 of each
leaf spring 16 in the construction shown~ forms the base
of a lead-in groove 18 on each side of the carrier 4
whereby the axle sections 13 are guided into position as
the carrier 4 is inserted into the housing 2. Such an
arrangement permits the carrier 4 to be snap engaged into
position, and allows ready release of the carrier 4 from
its pivotal mounting.
In the particular construction shown in the drawings,
the front end portion 19 of the carrier 4 projects beyond
the housing access opening 11~ and the sharpening device 5
is mounted on the carrier 4 adjacent the opening 11. The
sharpening device 5 may be mounted, as shown, for limited
rocking movement relative to the carrier 4~ and defines a
substantially V-shaped sharpening recess 21 (figure 8)
which is located below the uppermost surface 22 (figure 9)
of the carrier ~, at least during normal operation of
the assembly. The sharpening device 5 is exposed to the
upper surface 22 of the carrier ~ through a knife receiving
slot 23 (figure 8) which extends lengthwise of the
carrier 4, preferably on both the forward and rearward
sides of the sharpening device 5. Side surfaces of at
least portion of the slot 23 function as guide surfaces
to resist lateral tilting of a knife blade 7 inserted
into the housing 2. The base 2~ (figure 9) of the slot
portion 23a in the forward section of the carrier 4 may
also serve to guide a knife blade 7 into the sharpening
S~ 9.
1046774
recess 21 at an appropriate level, and at least part
of the base 25 of the slot portion 23b rearwar~ly of the
sharpening device 5 provides a rubbing surface which
is engageable by the blade cutting edge 26 for a purpose
hereinafter described. If desired, the upper surface 27
of the forwardly projecting portion 19 of the carrier 4
may form a ramp surface which is cooperable with a knife
handle 28 (see figure 3) as also hereinafter described.
The sharpening device 5 may be formed in any
suitable manner - for example, as is described in either
of Australian Patents 447~537 and 424,122 - and may be
connected to the carrier in a manner similar to that
described in Australian Patents 447~537.
The preferred carrier 4 shown in figures 3 to 13
of the drawings, includes a guide section 29 which is
pivotally connected to the main body 31 of the carrier 4
for movement between an operative position and a raised
inoperative position. In the operative position, as
shown in figures 8 and 9~ the guide section 29 defines
part of the upper surface 22 of the carrier 4 and includes
slot portion 23a which provides side guide surfaces for
a knife blade 7. It is preferred, as shown, that in the
operative position, the guide section 29 extends both
forwardly and rearwardly of the sharpening device 5.
rhe pivotal connection 32 between the carrier body 31 and
the guide section 29 is preferably located adjacent
the rear end of the guide section 29, so that when that
section is swung upwardly ( see figure 13 ) it exposes
the sharpening device ~ and a cavity 33 in the main body
31 of the carrier 4 which contains the sharpening device 5.
SM 10.
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Consequently, in that inoperative position, the
sharpening device 5 can be serviced as required
(e.g., cleaned), and debris resulting from sharpening
operations can be cleared from the cavity 33. The arrange-
ment is such that the guide section 29 can be moved
into the raised inoperative position while the carrier 4
is in its normal position within the housing 2~ but it
is usually convenient to do that when the carrier 4 is
removed from the housing 2. Any suitable means such as a
snap engageable latch may be employed to releasably
retain the guide section 29 in its operative position.
It is preferred that rocking movement of the
sharpening device 5 relative to the guide section 29 is
limited by stops 3~ and 35 formed on at least one side
of the cavity 33~ and that spring means 36 is provided to
urge the sharpening device 5 towards a means position.
In the construction shown, the spring means 36 comprises a
leaf spring formed integral with a mounting block 37
of the sharpening device 5~ and that spring (or any
alternative spring means as may be employed) is arranged
to provide the bias ad acent one side only of the sharpening
device 5. That is, the line of action of the bias is
located laterally of the centre line of the sharpening
recess 21~ and in that way a slight twist is imposed on
the sharpening device 5 which compensates for any
clearance in its pivotal mounting 38 (figures 6, 9 and 11)
and thereby tends to eliminate chatter during sharpening
operations.
Figures 9 and 11 show one particular method for
achieving the laterally disposed or offse~ bias in such a
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~046774
way that the bias is at respective opposite sides of
the sharpening recess 21 at each of the two limit positions
of the sharpening device 5. The two limit positions
are those at which the sharpening device 5 engages the
stops 34 and 35 respectively. The offset bias is
achieved by abutments 39 and 41 which project inwardly
from respective side walls 42 and 43 of the cavity 33
containing the sharpening device 5, and they are located
so that each is effective to product the bias and twist
as mentioned above, in a respective one of the limit
positions of the sharpening device 5.
It will be seen from figures 8 to 12 that the carrier
member 4 can be simply moulded from a suitable plastics
material, and assembled with little difficulty. In
particular~ the body 31 of the carrier member 4 comprises
two principal parts which can be easily assembled over
the sharpening device 5 and the guide section 29.
The reaction member 6 in the preferred construction
so far descrlbed, is located between the housing upper
wall 9 and the adjacent upper surface 22 of the carrier
and is pivotally connected to the housing 2 for movement
2bout an axis extending substantially parallel to the
pivctal axis of the carrier 4. The location of that pivotal
connection is preferably adjacent the housing upper wall
9 and some distance inwardly of the access opening 11 - for
example, adjacent the rear end of the carrier 4. Any
suitable means may be employed to form that connection,
but in the preferred construction shown, it comprises a
part cylindrical end section 44 of the reaction member 6
which is snap engageable within aligned recesses 45
provided in the two side walls 8 of the housing 2 (see
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figure 2). In that arrangement, the reaction member 6
may be released from the recesses 45 and withdrawn through
the front end of the housing 2 if required.
In the form shown, the reaction member 6 is shaped
somewhat as an inverted channel in cross-section so as to
define an upper wall 46 and two depending side walls
47 (see figures 6 and 7)~ The front end of the upper
wall 46 is adapted to bear on or lie close to the carrier
upper surface 22, preferably slightly forward of the
sharpening device 5, in the rest or closed condition of
the scabbard (figure 2) and may be provided with a downwardly
projecting lip 48 for that purpose~ A front reaction zone
is provided on the upper wall 46 of the reaction member
6 rearwardly of the lip 48, and in the construction shown~
it is formed by a downwardly projecting section 49 of
the wall 46. That zone 49 is preferably located almost
directly above the sharpening device 5, although it could
be positioned slightly rearwardly of that device if desired.
In addition, a rear reaction zone is provided intermediate
the reaction member pivot 44, 45, and the carrier pivot
13~ 14~ and in the construction shown~ that reaction zone
is defined by two downward projections 51 of the reaction
member upper wall 46, which projections51 are engageable
with the carrier upper surface 22 (see figure 4).
It is a feature of the invention that the pivot
connection 44, 45 of the reaction member 6 is located
rearwardly of the two reaction zones 49 and 51. Such
an arrangement contributes to successful operation of the
sharpener by permitting establishment of a desirable force
relationship. A further benefit of the pivot location is
S~ 13.
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that it enables the front end of the reaction member 6
to be moved through a substantial distance towards and
away fro~ the base 10 of the scabbard housing 2, and in
that way allows the scabbard to accept knife blades 7
of a wide range of depths.
When the scabbard is in the closed condition (figures
2 and 4), the rear reaction zone 51 preferably engages -the
carrier upper surface 22 at a location between the pivot
13~ 14 and rear end of the carrier 4, and the front reaction
zone may also engage the surface 22 but forwardly of the
carrier pivot 13~ 14. In any event, there is at least
one zone of engagement between the ~ction member 6 and the
carrier 4, and that is preferably at the rear reaction
zone 51.
Also in the closed condition~ the upper wall 46
of the reaction member 6 preferably forms a forward
continuation of the upper wall 9 of the housing 2, although
it may slope downwardly from the front edge 52 of the
housing wall 9 as shown in figure 2. The front edge
52 of the housing upper wall 9 is preferably located some
distance rearwardly of the front edge of each housing
side wall 8 so providing a gap 53 (figure 1) through
which the reaction member 6 can be lifted about its pivot.
In such a lifted condition however, the reaction member
side walls 47, which are slidably located between the
housing side walls 8, preferably extend below the upper
edges of the housing side walls 8 so as to retain a neat
appearance and provide substantially complete encapsulation
of a knife blade 7.
The biasing means in the preferred cons~ruction
SM 14.
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shown, acts directly on the reaction member 6, and in that
respect is distinguished over prior art constructions
in which the biasing means acts on the knife blade
or a pivoted carrier for the sharpening device. It is
usually preferred to use a leaf or wire spring as the
biasing means, and to arrange such a spriny to act on
the reaction member 6 forwardly of the axis of pivot 44,
45 so as to force the front end downwardly towards the
base 10 of the scabbard housing 2. If desired, the
biasing means may comprise two separate sections which
act independently of each other against the carrier 4 and
the reaction member 6 respectively so as to normally hold
those members in a closed condition as shown in figure 2.
Preferably however, the biasing means acts between those
two members 4 and 6~ and for that purpose may comprise a
one-piece somewhat U-shaped spring 54 as shown in the
drawings. If desired, there may be one such spring adjacent
each side of the carrier 4.
The particular biasing spring 54 shown~ includes
two legs 55 and 56 interconnected through a curved bight
portion 57 which, in the operative position of the spring
54 as shown in the drawings, is located in the housing
passage 3 rearwardly of both the carrier 4 and the reaction
member 6~ and the two legs 55 and 56 extend forwardly
in the direction of the passage 3. The forward end portion
58 of the leg 55 engages the carrier 4, preferably directly
below the sharpening device 5, and the forward end portion
59 of the leg 56 engages the reaction member 6, also prefer-
ably adjacent the sharpening device 5 and/or in the region
of the reaction zone 49. Such a biasing spring is
SM 15.
104677~
arranged to apply a scissors action between the reaction
member 6 and the carrier 4 so that the former is urged
downwardly about its respective pivot 44, 45 and the
latter is urged upwardly about its pivot 13, 14.
It is preferred that the scabbard housing 2 is
arranged so that a knife blade 7 can be inserted into the
passage to such depth that the heel or choil 61 of the
blade 7 is located rearwardly of -the sharpening device 5
(see figure 5), and thereby permits substar.tially full
length sharpening of the blade cutting edge 26. In that
fully inserted position, part 62 of the knife handle 28
may rest on the ramp surface 27 of the carrier 4 so that
the blade is retained at an appropriate height for withdrawal
back across the sharpening device 5. That ramp surface
27 is preferably sloped as shown so that during the final
part of the insertion of a knife blade 7 into the housing
2~ the blade 7 is lifted progressively to permit sharpening
of a curved choil 61.
When a knife blade 7 is first inserted into the
scabbard described, the upper edge 63 preferably engages
the front lip 48 of the reaction member 6 at substantially
the same time as the cutting edge 26 engages the sharpening
device 5~ as is shown diagrammatically in figure 14.
At that stage, the spring force S resists separation of
the members 4 and 6~ and the member 4 is maintained in
equilibrium about the pivot 13 by the reactions R1 and R2
at the zones of engagement between the members 4 and 6.
As the blade 7 is moved deeper into the housing 2,
the front end of the carrier 4 is caused to swing downwardly
about the pivot 13 because of the pressure applied at
SM 16.
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the sharpening device 5~ and the blade upper edge 63
contacts the front reaction zone 49 of the reaction member
6 (see figure 15). At the same time, the front end of
the reaction member 6 is caused to swing upwardly about
its pivot 44 because of the engagement between zone 49
and the blade upper edge 63. The rear reaction zone 51
of the reaction member 6 is still in engagement with the
carrier 4 and consequently keeps the carrier 4 in a
satisfactory position relative to the knife blade 7.
I~ the particular form of the invention shown~
continued movement of the knife blade 7 into the housing
2 results in the blade cutting edge 26 engaging the rubbing
surface 25 rearwardly of the sharpening device 5, so that
the blade 7 then has two point engagement with the carrier
4 on opposite sides respectively of the carrier pivot 13 (see
figure 16). At or about that time, the rear reaction zone
51 of the reaction member 6 may be lifted clear of the
carrier 4 and the knife blade 7, the sharpening device S
can function to form a substantially constant cutting
angle on the blade 7. It may be, however, that the
carrier 4 and the reaction zone 51 remain in engagement
durlng th~ entire sharpening operation.
When the figure 16 condition has been reached,
the reaction forces are such that the carrier 4 and blade
7 retain the particular relationship regardless of the
disposition of the blade 7 relative to the housing 2.
Reaction R1 no longer exists because of separation of the
zone 51 from the carrier 4, but reaction R4 between the
blade 7 and carrier 4 stabilizes the carrier 4 in that
it balances the reaction R3 on the opposite side of the
S~ 17.
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pivot 13. Thus~ assuming that the knife blade 7 is
maintained at a particular position of insertion and
the knife handle 28 is moved upwardly or downwardly
relative to the housing 2, the relative positions of the
reaction member 6, carrier 4, and knife blade 7 will
remain the same within the limits of movement of the first
mentioned two components 6 and 4.
As a result of the foregoing, the relative positions
of the carrier 4 and the knife blade 7 are controlled
in such a way that the sharpening device 5 can function
to produce a substantially constant cutting angle on
the blade. Any change in those relative positions as
will naturally occur because of the changing configuration
of the blade 7 as it is inserted further into the housing
2~ may be such as to substantially compensate for that
change in configuration so that the cutting angle is
maintained substantially constant.
Figures 17 and 18 show the blade 7 at progressively
greater stages of penetration into the housing 2. Line
CR1 in figures 16 to 18 represents the line of the direction
of the force applied between the blade 7 and the cutters
of the sharpening device 5 during inward movement of the
blade 7. It will be seen that the angular relationship
between that line and the longitudinal axis of the blade 7
does not vary significantly throughout~ so that there is
little variation in the resistance to sharpening during
the entire operation. The line CR2 in figure 18 repres-
ents the direction of the cutter resistance force during
withdrawal of the blade 7 from the housing 2, and the
angular relationship between line CR2 and the blade
SM 18.
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longitudinal axis is much the same as that between
line CR1 and the blade longitudinal axis.
It will be appreciated from the foregoing that
a proper relationship between the knife blade 7 and the
sharpening device 5 is maintained during movement of
the blade 7 into and out of the scabbard housing 2.
That results from the two point engagement with the carrier
4, which is achieved during at least part of that movement
by engagement of the knife blade 7 and the reaction member
6 respectively at spaced zones. ln the particular arrange-
ment described, during part of the blade movement, the
aforementioned relationship is achieved by engagement of
the carrier 4 with two spaced zones of the blade 7.
It is also relevant that the two zones of engagement with
the carrier 4 are on opposite sides of the carrier pivot
13, so that the blade 7 and carrier ~ rock about that
pivot 13 without loss of the desired relationship~
should the knife handle 2~ be moved up or down relative to
the scabbard housing 2. The reaction member 6 will of
course follow any such movement of the carrier 4 and blade
7 because of its pivotal mounting 4g~ 45 and bias
condition. When the knife blade 7 is being withdrawn
from the housing 2, there will be the same control over the
blade 7 and sharpening device 5 relationship.
A construction as described has several advantage~
over prior scabbard-sharpener combinations. For example,
it has the ability to maintain a substantially constant
cut~ing angle on the knife blade in the manner described
above. In the preferred construction described in which
the carrier and reaction member are biased by the same
SM 19~
10~6~7~
spring, the foregoing feature is especially pronounced
because of the dynamic nature of the resulting sharpening
assembly. That is~ the assembly (carrier~ reaction member
and biasing spring) is able to move relative to the housing
without disturbing the biasing force, which is the pressure
between the knife blade and the sharpening device and
without disturbing the blade and the sharpening device
relationship.
Another advantage results from the rearwardly
located engagement between the reaction member and the
carrier~ during initial insertion of a knife blade.
The location of that engagement provides suitable compen-
sation between the force acting between the blade and
sharpening device and that applied to the knife handle
by the user~ and that location will usually be dependant to
some degree on the profile of the blade to be sharpened.
In all in~tances however, it will be between the carrier
and reaction member pivots and rearwardly of the former.
Still another advantage arises from the two
20 ~ point connection between the knife blade and the carrier.
As the knife blade engages the aforementioned rubbing
surface (which may be provided by an insert of suitable
material attached to the carrier~ or it may be a integral
part of the carrier) it is also in engagement with the
sharpening device~ and the result is that there is a
reduction of the force applied to the sharpening device.
In practice that reduction might be as high as 50%. It
is found that the load on the sharpening device is seldom
constant because of fluctuations in pressure as applied
by the user~ and the effective reduction in load as
SM ~ 20.
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resulting from the aforementioned arrangement enables
a greater control of the sharpening operation.
Yet another advantage results from the provision
of a lead-in guide surface formed by the base of the blade
receiving slot on the front side of the sharpening device~
as that facilitates entry of the knife blade into the
scabbard. Also, the ramp surface engagement with the
knife handle allows the sharpening action to proceed
past the choil of the blade and prevents the knife handle
dropping at the completion of the inward sharpening
operation. Consequently, withdrawal of the blade from
the scabbard is not hindered and the outward sharpening
operation may be effected in a convenient and simple manner.
Various alterations, modifications and/or additions
may be incorporated into the invention particularly
described without departing from the spirit or scope of
the invention as defined by the appended claims.
S~ 20a.
