Title: Knife and apparatus for clamping a knife
Abstract: A knife and apparatus for clamping the knife. The knife has front and back sides that, preferably, both include interlocking features adapted for interlocking engagement with corresponding inner and outer clamping members, to prevent slippage of the knife from the clamping members in orientations wherein the knife rests thereon in the chipping apparatus when the knife is unclamped. Preferably, the interlocking feature of the back side of the knife includes a semi-cylindrical groove, and the interlocking feature of the front side of the knife includes two spaced-apart deflector ridges. Preferably, the interlocking feature of the outer clamping member is a projection having a semi-cylindrical tip portion wherein the semi-cylindrical shape is preferably half-cylindrical, and wherein the projection extends from an inner surface of the outer clamping member sufficiently far that most of the back side of the knife does not make contact therewith.
Patent Number: 6,968,879 Issued on 11/29/2005 to Schuh, et al.
| Inventors:
|
Schuh; Loren R. (Battle Ground, WA);
Simonsen; Tobias L. (Vancouver, WA)
|
| Assignee:
|
Key Knife, Inc. (Tualatin, OR)
|
| Appl. No.:
|
918895 |
| Filed:
|
July 30, 2001 |
| Current U.S. Class: |
144/174; 144/176; 144/218; 144/241; 241/92 |
| Intern'l Class: |
B27C 001/00 |
| Field of Search: |
144/1621,176,218,230,241,172-174,220
241/91-93,189.1,278.1,292.1,296,298
407/30,35,49,80,91,107,108,41,51
|
References Cited [Referenced By]
U.S. Patent Documents
| 1222871 | Apr., 1917 | Jesseph.
| |
| 3780778 | Dec., 1973 | Chapman.
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| 3838724 | Oct., 1974 | Buchacher et al.
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| 3976112 | Aug., 1976 | Rowlson et al.
| |
| 3981337 | Sep., 1976 | Sundstrom.
| |
| 3989077 | Nov., 1976 | Humbert.
| |
| 4047670 | Sep., 1977 | Svensson.
| |
| 4220186 | Sep., 1980 | Sybertz.
| |
| 4271882 | Jun., 1981 | Valo.
| |
| 4327789 | May., 1982 | Reuter.
| |
| 4335767 | Jun., 1982 | Reuter.
| |
| 4351487 | Sep., 1982 | Haller et al.
| |
| 4545413 | Oct., 1985 | Sundberg et al.
| |
| 4610285 | Sep., 1986 | Derivaz.
| |
| 4848427 | Jul., 1989 | Reuter.
| |
| 5271440 | Dec., 1993 | Bradstreet, Jr. et al.
| |
| 5421386 | Jun., 1995 | Lundstrom.
| |
| 5469902 | Nov., 1995 | Sharp et al.
| |
| 5564967 | Oct., 1996 | Jorgensen.
| |
| 5617908 | Apr., 1997 | Toogood.
| |
| 5709255 | Jan., 1998 | Toogood.
| |
| 5816301 | Oct., 1998 | Stager.
| |
| 5819826 | Oct., 1998 | Schmatjen.
| |
| 5904193 | May., 1999 | Kellner.
| |
| 5979522 | Nov., 1999 | Swartwood.
| |
| 6058989 | May., 2000 | LaGrange et al.
| |
| 6058992 | May., 2000 | Stager et al.
| |
| 6131627 | Oct., 2000 | Zaiser.
| |
| 6167929 | Jan., 2001 | Stager et al.
| |
| Foreign Patent Documents |
| 397 629 | Feb., 1990 | AT.
| |
| 2760674 | Mar., 1997 | FR.
| |
Primary Examiner: Banks; Derris H.
Assistant Examiner: Self; Shelley
Attorney, Agent or Firm: Birdwell & Janke, LLP
Claims
1. A wood chipping apparatus, comprising:
a knife having a back side, said back side having a first semi-cylindrical interlocking
feature therein, and a front side, wherein said front and back sides co-terminate
in two spaced apart cutting edges lying in a plane, said front side including,
in correspondence with said cutting edges, a respective two spaced apart and similar
projecting interlocking features that project a maximum distance from said plane, and
an inner clamping member comprising a projection terminating in a second semi-cylindrical
interlocking feature that is complementary in form to said first interlocking feature
for engagement therewith, for clamping said knife in the wood chipping apparatus,
said projection extending from said inner clamping member so as to permit rotation
of said knife relative thereto during said engagement.
2. The apparatus of claim 1, wherein said projecting interlocking features include,
corresponding with said cutting edges, two spaced apart deflector ridges projecting
away from said front side a maximum distance from said plane.
3. The apparatus of claim 2, further comprising an outer clamping member adapted
to interlockingly receive at least one of said deflector ridges during said engagement.
4. The apparatus of claim 2, wherein said first semi-cylindrical interlocking
feature is a recess, and wherein said second semi-cylindrical interlocking feature
is convex.
5. The apparatus of claim 1 the apparatus further comprising an outer clamping
member adapted to interlockingly receive at least one of said projecting interlocking features.
6. A wood chipping apparatus, comprising:
a knife having a back side, said back side having a first semi-cylindrical interlocking
feature therein, and a front side, wherein said front and back sides co-terminate
in two spaced apart cutting edges lying in a plane, said front side including,
in correspondence with said cutting edges, a respective two spaced apart and similar
projecting interlocking features that project a maximum distance from said plane, and
a clamp for clamping said knife by applying a clamping force thereto, said clamp
comprising a projection terminating in a second semi-cylindrical interlocking feature
that is complementary in form to said first interlocking feature for engagement
therewith, substantially the entirety of said clamping force being transmitted
through said engagement.
7. The apparatus of claim 6, wherein said projecting interlocking features include,
corresponding with said cutting edges, two spaced apart deflector ridges projecting
away from said front side a maximum distance from said plane.
8. The apparatus of claim 7, further comprising an outer clamping member adapted
to interlockingly receive at least one of said deflector ridges during said engagement.
9. The apparatus of claim 7, wherein said first semi-cylindrical interlocking
feature is a recess, and wherein said second semi-cylindrical interlocking feature
is convex.
10. The apparatus of claim 6 the apparatus further comprising an outer clamping
member adapted to interlockingly receive at least one of said projecting interlocking features.
11. The apparatus of claim 4, wherein each said deflector ridge terminates in
a single linear edge disposed said maximum distance from said plane.
12. The apparatus of claim 4, wherein each of said deflector ridges defines an
associated knife-edge-joining portion providing a smoothly curving transition from
a point on the deflector ridge that is disposed from said plane said maximum distance
to a corresponding point on the corresponding cutting edge.
13. The apparatus of claim 3, wherein each said deflector ridge terminates in
a single linear edge disposed said maximum distance from said plane.
14. The apparatus of claim 3, wherein each of said deflector ridges defines an
associated knife-edge-joining portion providing a smoothly curving transition from
a point on the deflector ridge that is disposed from said plane said maximum distance
to a corresponding point on the corresponding cutting edge.
15. The apparatus of claim 2, wherein each said deflector ridge terminates in
a single linear edge disposed said maximum distance from said plane.
16. The apparatus of claim 2, wherein each of said deflector ridges defines an
associated knife-edge-joining portion providing a smoothly curving transition from
a point on the deflector ridge that is disposed from said plane said maximum distance
to a corresponding point on the corresponding cutting edge.
17. The apparatus of claim 9, wherein each said deflector ridge terminates in
a single linear edge disposed said maximum distance from said plane.
18. The apparatus of claim 9, wherein each of said deflector ridges defines an
associated knife-edge-joining portion providing a smoothly curving transition from
a point on the deflector ridge that is disposed from said plane said maximum distance
to a corresponding point on the corresponding cutting edge.
19. The apparatus of claim 8, wherein each said deflector ridge terminates in
a single linear edge disposed said maximum distance from said plane.
20. The apparatus of claim 8, wherein each of said deflector ridges defines an
associated knife-edge-joining portion providing a smoothly curving transition from
a point on the deflector ridge that is disposed from said plane said maximum distance
to a corresponding point on the corresponding cutting edge.
21. The apparatus of claim 7, wherein each said deflector ridge terminates in
a single linear edge disposed said maximum distance from said plane.
22. The apparatus of claim 7, wherein each of said deflector ridges defines an
associated knife-edge-joining portion providing a smoothly curving transition from
a point on the deflector ridge that is disposed from said plane said maximum distance
to a corresponding point on the corresponding cutting edge.
23. The apparatus of claim 1, wherein said first semi-cylindrical interlocking
feature is a recess, and wherein said second semi-cylindrical interlocking feature
is convexly curved.
24. The apparatus of claim 6, wherein said first semi-cylindrical interlocking
feature is a recess, and wherein said second semi-cylindrical interlocking feature
is convexly curved.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a knife and apparatus for clamping a knife in
a wood chipper, such as a disc, drum or conical head chipper for use in the commercial
processing of logs.
In wood chipping apparatus used in the forest products industry, a rotating member
is provided for receiving replaceable knives for cutting chips from the log. Each
knife is typically clamped to the rotating member between an outer clamping member
and an inner clamping member or counterknife, wherein the knife and counterknife
together form a surface against which the log is forced to remove chips from the
log. The chips themselves have commercial value, and their removal shapes the log
into lumber and finishes its surface. The clamping members essentially form a cassette
for the knife, although the entire cassette is often referred to in the trade as
a knife. Herein, the term "knife" is used to refer to the blade that is clamped
between the outer and inner clamping members.
The spacing between the outer and inner clamping members is adjustable for loading
the knife into the apparatus, or unloading the knife from the apparatus, such as
for replacing the knife or turning the knife end-to-end to position an alternative
knife edge in the chipper. A preferred mechanism for adjusting the spacing between
an outer clamping member an inner clamping member is described in U.S. Pat. No.
5,979,522, also incorporated herein by reference in its entirety.
As one example of a wood chipping apparatus, a chipper disc typically spins in
a vertical plane. A number of identical knives are spaced around the periphery
of the disc. The knives are elongate, and their elongate axes are oriented along
radial lines passing approximately through the center of the disc, the axis of
each knife becoming horizontal at respective 9:00 and 3:00 positions of the disc.
When unclamped, the knives are typically unrestrained from sliding along these
radial lines, so it is preferable to unclamp the knives when they are at least
approximately in one of these two level positions.
A shroud is typically provided that covers the disc to retain chips and to shield
personnel, the shroud including a closeable opening in a predetermined angular
position of rotation of the disc, to provide access to a knife that has become
aligned therewith. The position of the opening is selected so that the heavy and
sharp knife will not slip forwardly out of the apparatus when it is unclamped;
however, even so, the knife remains free to slip backwardly into the apparatus
and still presents some risk of injury or damage. Such considerations are important
as well to other types of wood chippers, such as the drum and conical head chippers.
Accordingly, there is a need for a knife and apparatus for clamping
the knife in a chipping apparatus that provides for more safely and securely preventing
movement of an unclamped knife along a line of slippage extending into and out
of the apparatus.
SUMMARY OF THE INVENTION
A knife and apparatus for clamping the knife according to the present invention
solves the aforementioned problem and meets the aforementioned need by providing
an elongate knife having front and back sides co-terminating in a cutting edge,
and outer and inner clamping members for clamping the knife therebetween adapted
to receive, respectively, the back and front side of the knife. The back side of
the knife and the outer clamping member have mutually interlocking features to
prevent slippage of the knife from the outer clamping member in orientations wherein
the knife rests thereon in the chipping apparatus when the knife is unclamped.
The front side of the knife and the inner clamping member preferably also have
mutually interlocking features to prevent slippage of the knife from the inner
clamping member in orientations wherein the knife rests thereon in the chipping
apparatus when the knife is unclamped.
In one aspect of the invention, the interlocking feature of the back side of
the
knife includes at least one semi-cylindrical groove, wherein the knife is preferably
bilaterally symmetric about a plane parallel to the elongate axis of the knife
and wherein the semi-cylindrical shape is preferably half-cylindrical.
In another aspect of the invention, the interlocking feature of the outer clamping
member is a projection having a semi-cylindrical tip portion wherein the semi-cylindrical
shape is preferably half-cylindrical.
In yet another aspect of the invention, the projection of the outer clamping
member
extends from an inner surface thereof sufficiently far that most of the back side
of the knife does not make contact therewith, to better control the point of application
of clamping force.
Where the tip portion of the projection is semi-cylindrical, a degree of rotation
of the knife about the projection is permitted which facilitates installation of
the knife and which accommodates a greater degree of dimensional variance in the
mating parts, further facilitating installation of the knife as well as reducing
manufacturing costs.
Therefore, it is a principal object of the present invention to provide
a novel and improved knife and apparatus for clamping the knife.
It is another object of the present invention to provide a knife and apparatus
for clamping the knife that provides for more safely holding the knife in position
in a chipping apparatus when the knife is unclamped therein.
It is yet another object of the present invention to provide a knife and apparatus
for clamping the knife that provides for more securely holding the knife in position
in the chipping apparatus when the knife is unclamped therein.
It is still another object of the present invention to provide a knife and apparatus
for clamping the knife that facilitates installation and removal of the knife from
the chipping apparatus.
It is a further object of the present invention to provide a knife and apparatus
for clamping the knife that provides for reduced manufacturing costs of the knife
and clamping members.
It is still a further object of the present invention to provide a knife and
apparatus
for clamping the knife that provides for increased control over the application
of clamping force to the knife.
The foregoing and other objects, features and advantages of the present invention
will be more readily understood upon consideration of the following detailed description
of the invention, taken in conjunction with the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a pictorial view of a knife according to the present invention, showing
is a front side of the knife in perspective.
FIG. 1B is a pictorial view of the knife of FIG. 1 showing a back side of the
knife in perspective.
FIG. 2A is an elevation of a disc chipper including a plurality of knives such
as that shown in FIGS. 1A and 1B.
FIG. 2B is a cross-section of the disc chipper of FIG. 2A, taken through a knife
that is in the 3:00 position of the disc along a line 2B—2B,
showing the knife clamped in the disc chipper.
FIG. 3A is a cross-section of the disc chipper of FIG. 2B, taken through another
knife that is in the 9:00 position of the disc along a line 3A—3A
thereof, showing the knife unclamped in the disc chipper.
FIG. 3B is a cross-section of the disc chipper and knife of FIG. 2B, showing
the knife in the 3:00 position unclamped in the disc chipper.
FIG. 4A is a partial cross-section, corresponding to the cross-section of FIG.
3B in the 3:00 position, of a knife and outer clamping member according to the
present invention.
FIG. 4B is a partial cross-section of the knife and outer clamping member of
FIG. 4A, showing the knife clamped between the outer clamping member and an inner
clamping member.
FIG. 5A is a pictorial view, corresponding to FIG. 1A, of a knife according
to the present invention that illustrates an alternative to the knife shown therein.
FIG. 5B is a pictorial view, corresponding to FIG. 1B, of a knife according
to the present invention that illustrates an alternative to the knife shown therein.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to FIGS. 1A and 1B, a preferred knife
10 is shown modified
according to the present invention. The knife without modification has been widely
available as manufactured by Key Knife, Inc., of Tualatin, Oreg., and is described
in detail in Schmatjen, U.S. Pat. No. 5,819,826, herein incorporated by reference
in its entirety. The knife
10 may be employed in any wood chipping apparatus,
such as a disc, drum or conical head wood chipper. The knife has an elongate axis
"L", a front side
12 and a back side
14.
The front side
12 of the knife
10 includes spaced deflector ridges
18a and
18b that project therefrom. Each of the deflector
ridges
18a and
18b is characterized by a single linear
edge
13a and
13b respectively (FIG. 1A). The deflector
ridges define a channel
34 having a channel surface
34a. The
channel
34 is effectively a recess in the front side of the knife, which
may be provided in other configurations, such as a keyway. The deflector ridges
also define two lower knife-edge-joining portions
38a and
38b
that terminate in respective cutting edges
16a and
16b.
The cutting edges
16a and
16b lie in a plane "P
l"
and the edges
13aand
13bof the deflector ridges are
maximally spaced from the plane "P
l." As is most readily apparent in
FIG. 1A, the lower knife-edge-joining portions
38a and
38b
provide smoothly curving transitions between the associated linear edges
13a
and
13b and the respective corresponding cutting edges
16a
and
16b. Particularly, with reference (for example) to the knife-edge-joining
portion
38a, the knife-edge-joining portion provides a smoothly curving
transition between a point "P
deflector-ridge" on the linear edge
13a
and a point "P
cutting-edge" on the cutting edge
16a.
The back side
14 of the knife
10 includes a clamp-facing surface
portion
14a that is substantially planar and parallel to the channel
surface
34a, and two upper knife-edge-joining portions
35a
and
35b that slope from opposite edges of the clamp-facing surface
portion to the cutting edges
16a and
16b. The knife
10 is typically provided so that the lower knife-edge-joining portion
38a
lies in the same plane as the lower knife-edge-joining portion
38b
(and the channel surface
34a); however, these faces can be ground
or otherwise provided according to the aforementioned companion application entitled
METHOD AND APPARATUS FOR CLAMPING A KNIFE so that the lower knife-edge-joining
portions are not coplanar.
As mentioned previously, the above features are described in the '826 Patent.
While the invention is believed to provide maximum advantage when used in connection
with the preferred knife, the invention will provide an advantage when used with
other prior art knives as well, such as knives that do not have all of the aforementioned
features, or knives which include additional features.
Referring to FIG. 2A, a disc chipper
20 is shown employing a plurality
of the knives
10. While a disc chipper is used herein to illustrate use
of particular embodiments of the invention, the principles of the invention apply
equally to other chipping apparatus including that employing a drum or a "conical"
head, and application of those principles to alternative configurations of chipping
apparatus will be readily apparent to those of ordinary skill in the art.
The knives are elongate, meaning herein that they have a shape in a cross-sectional
plane that is maintained for some distance along an axis "A" that is perpendicular
to the plane. For use in a disc chipper, the length of the knives along the axis
"A" is typically large in comparison to the cross-sectional dimensions of the knives;
however, the length of the knives may be small in comparison to these dimensions,
such as where many discs are combined to form a drum in a drum chipping apparatus.
In the disc chipper, the elongate axes "A" extend radially, approximately from
the center of the disc. The disc spins in a vertical plane in the direction of
the arrow, with an exposed cutting edge
16a of each knife being visible.
FIG. 2B shows a cross-section of the disc chipper
20 taken through a
particular knife
10a that is in the 3:00 position of the disc as
it is shown in FIG. 2A. The knife is shown clamped in the disc chipper between
outer and inner clamping members
22a and
24a respectively,
so that the disc is ready for use for cutting wood. The inner clamping member is
often referred to as a "counterknife."
An insert
21 is received in a corresponding pocket in the disc chipper.
The insert supports the outer and inner clamping members as well as means for adjusting
the spacing between the clamping members for clamping and unclamping the knife.
For clamping the knife as shown, at least a portion of the channel surface
34a
(FIG. 1A) is abuttably received by the inner clamping member
24a,
and the clamp-facing surface portion
14a of the back side
14
of the knife (FIG. 1B) is at least disposed proximate to (FIG. 4B) and may be abuttably
received by an inner surface
23 (FIG. 3A) of the outer clamping member
22a.
Preferably, the outer clamping member
22a is fixedly disposed
with respect to the insert
21, and a threaded adjustment member
26a
is received in a corresponding threaded aperture through the outer clamping
member which permits translating the adjustment member in the directions indicated
by the arrows, for adjustably pivoting the inner clamping member
24a
about a bearing surface
33 that is provided as part of the insert
21.
Alternatively, the position of the inner clamping member may be fixed and the outer
clamping member may be adapted to be adjustably spaced apart therefrom, and either
or both clamping members may be adjustably movable by any desired means without
departing from the principles of the invention.
Turning to FIG. 3A, a cross-section similar to that of FIG. 2B shows another
knife
10b (see also FIG. 2A) which is in the 9:00 position of the
disc. By contrast to the knife
10a in FIG. 2B, the knife
10b
is unclamped in the disc chipper. The inner clamping member
24b for
the knife
10b has been pivoted about the surface
33 to provide
a spacing from the outer clamping member
22b that is sufficient for
removing the knife from, or installing the same knife or a different knife, between
the clamping members. When the clamping members
22b and
24b
are separated, the knife
10b in the 9:00 position rests on the
inner clamping member
24b under the influence of gravity.
More particularly, one of the deflector ridges
18a is disposed
outside a toe
19 of the inner clamping member
24b at one end
of the toe, the other end of the toe being defined by a recess
28 shaped
to receive the other of the other deflector ridge
18b. The channel
34 as bounded by the deflector ridges defines a recess that, along with
the relatively projecting toe of the inner clamping member, provide interlocking
means which cooperate to hold the knife
10b to the inner clamping
member
24b against the influence of gravity when the knife is unclamped
in the 9:00 position of the disc. Alternatively, a keyway may be provided in the
knife for receiving the toe. However, if the knife is dislodged, it may fall outwardly
from the disc chipper along a line of slippage "B," posing a substantial risk of
injury or damage.
Interlocking the knife to the inner clamping member also provides for
locating and positioning the knife ("indexing") so that it is accurately disposed
for cutting when the clamping members are adjusted to clamp the knife therebetween.
Turning to FIG. 3B, a cross-section similar to that shown in FIG. 2B illustrates
the knife
10a unclamped in the disc chipper in the 3:00 position
of the disc. The inner clamping member
24a has been pivoted about
the surface
33 to provide a spacing from the outer clamping member
22a
that is sufficient for removing the knife from, or installing the same knife
or a different knife, between the clamping members. When the clamping members
22a
and
24a are separated, such as by use of the adjustment mechanism
26a, the knife
10a in the 3:00 position of the disc
rests on the outer clamping member
24a under the influence of gravity
as shown. It may be noted that the clamping members need not be maximally separated
for this result to occur, the clamping members becoming separated at the point
that the clamping force they exert on the knife is reduced to zero.
The knife
10a in the 3:00 position cannot be interlocked with the
inner clamping member
24, hence the safety and indexing features provided
by the deflector ridges of the knife and the recess
28 of the inner clamping
member are lost in this position. Thence, the unclamped knife in the 3:00 position
of the disc will ordinarily slip backwardly into the apparatus along the line of
slippage "B," against interior portions of the outer and inner clamping members.
While the risk of injury to personnel is much reduced as compared to that posed
by slippage of the knife in the 9:00 position, such slippage may cause damage to
the knife or the apparatus, and may make removal of the knife somewhat difficult.
Moreover, installation of the knife is also difficult, and indexing the knife into
proper position while clamping the knife is very difficult.
With additional reference to FIG. 1A, to improve the safety and security of
holding the unclamped knife in the 3:00 position of the disc as well as to provide
for indexing of the knife, the knife and outer clamping members are provided with
interlocking features to prevent slippage of the knife into or out of the apparatus
along the axis "B" (FIG. 3B) when the knife is unclamped, providing an outstanding
advantage over the prior art.
In a preferred embodiment of the invention, the otherwise substantially planar
clamp-facing surface portion
14a of the back side
14 of the
knife includes a recess
30 that is particularly a groove, and the outer
clamping member
22 includes a complementary elongate projection
32
adapted to fit into the groove, where persons of ordinary skill will immediately
recognize the equivalence of providing the knife with a projection and the outer
clamping member
22 with a complementary and corresponding groove. According
to the invention, the interlocking features of the knife and outer clamping member
may be any interlockingly cooperating male or female structures that permit removing
the knife from the outer clamping member while preventing the aforementioned slippage.
Preferably, the interlocking features interlock or retain one another
in the direction or plane of slippage "B" while providing for free movement of
the knife in one or both perpendicular directions. As mentioned, the recess
30
and projection
32 are preferably elongate, and at least a portion of each
is preferably semi-circular as seen in a cross-section perpendicular to the elongate
axis "L" (FIG. 1A), to provide surfaces that are semi-cylindrical. Most preferably
and particularly as shown, the shape of the recess
30 and the shape of a
distal tip
27 (best seen in FIG. 4B) of the projection in cross-section
are half-circular, to provide surfaces that are half-cylindrical.
These shapes are believed to be especially advantageous for easing installation
of the knife, by permitting the knife to pivot on the projection about the elongate
axis of the knife which facilitates manipulating the knife into position, and by
accommodating greater manufacturing tolerances, which further reduces the effort
required to place the knife into position as well as manufacturing costs.
Referring to FIGS. 4A and 4B, the preferred form of the interlocking features
provides that the projection
32 extends far enough from the inner surface
23 of the outer clamping member so that a "three-point" contact is provided
for clamping the knife, wherein the projection
32 provides one of the points
of contact. In FIG. 4A, the inner clamping member
24 has been moved away
from the outer clamping member
22, and the knife
10 is held loosely
by the projection
32. In FIG. 4B, the clamping member
24 has been
pivoted to receive the front side
12 of the knife and clamp the knife to
the projection
32 of the clamping member
22, wherein the projection
32 has sides
32a and
32b that are substantially
perpendicular to the inner surface
23 of the clamping member
22,
terminating in a tip
27 having the semi-circular cross-section, and extending
far enough from the surface
23 so that the knife can rotate (compare FIGS.
4A and 4B) about its elongate axis at the tip
27, and so that the back side
of the knife is not otherwise in contact with the surface
23 when the knife
is clamped (FIG. 4B).
Permitting a minimal but significant ("substantial") degree of rotation
of the knife on the projection facilitates installation of the knife while not
defeating the purpose of the projection to interlock with the recess
30
to prevent slippage. The semi-cylindrical surface of the projection may extend
over an arc that is greater or less than a half-cylindrical 180 degrees, while
the semi-cylindrical surface of the recess
30 should have an arc that is
about 180 degrees or less, to prevent the recess
30 from pinching or capturing
the projection, which would decrease the efficacy of the connection between the
parts and make both removal and installation of the knife difficult.
As mentioned, providing that most of the back side of the knife does not contact
the surface
23 when the knife is clamped provides for a "three-point" contact,
i.e., a point of contact "A
1" at the tip
27 falls between, with respect
to a line "P
1," two other points of contact "A
2" and "A
3,"
so that contact is not being made, and force is not being transmitted, between
most of the back side of the knife
14 and the clamping member
22.
This provides a means for applying the clamping force that is consistent in spite
of manufacturing variations in the dimensions of the parts.
The semi-cylindrical shapes for the projection and recess
30 are also
believed to decrease manufacturing cost by rendering the capability to index the
knife accurately to the outer clamping member less sensitive to manufacturing tolerances
in these features.
While in the preferred embodiment these features extend over the entire length
of the knife (determined in the direction of the axis "L"), this is not essential,
and it may provide some additional indexing capability to limit the lateral extent
of the interlocking features, so that the knife is retained laterally (into and
out of the plane of FIG. 3A) as well as with respect to slippage in the direction
or plane "B." However, the knife may be freely moved away from the inner clamping
member
22a along the perpendicular direction "C," for changing the knife.
Preferably, the interlocking feature of the knife is located so that
the knife is or remains bilaterally symmetric with respect a plane "P" (FIG. 1B)
that is parallel to the elongate axis of the knife, so that the knife may be turned
end-to-end in a perpendicular plane, rather than rotated about the elongate axis,
such as is required in Valo, U.S. Pat. No. 4,271,882 or Svensson, U.S. Pat. No.
4,047,670, for example, to obtain a fresh cutting edge from the knife. In view
of the sharp edges of the knives and their great weight, it is believed that the
former operation is easier to perform than the latter as it can be performed without
touching the cutting edges, without holding both sides of the knife, and without
requiring a rotation of the wrist.
It should be noted that to provide such symmetry does not require a single interlocking
feature that is centered on or in the back side
14 of the knife such as
shown in FIG. 1B. For example, bilateral symmetry with respect to the plane "P"
may be obtained by providing an interlocking feature of the knife consisting of
two, or any even number of recesses
30 that are symmetrically disposed with
respect to the plane, either alone or in combination with a recess
30 that
is centrally disposed in the plane. This provides the option of applying clamping
force to the back side of the knife off its center.
To permit the aforementioned pivoting of the knife about the projection, it is
preferable that only one projection is provided that is adapted to be received
in just one of the one or more recesses
30 that are provided. However, providing
this advantage is not essential, and additional projections may be provided without
departing from the principles of the invention.
Other forms and shapes of the interlocking features may be provided also without
departing from the principles of the invention. For example, the one or more projections
could be formed as pins and the one or more recesses as complementary apertures,
holes or cavities providing for free movement along the axis "C" even though sliding
the knife laterally is not permitted without first separating the pins from the
holes by movement of the knife along the axis "C." A similar effect is obtained,
as mentioned above, by forming the preferred groove so that it does not extend
the entire length of the knife.
Provision of the recesses
30 (FIG. 3A) and projections
32
makes it particularly advantageous to access the knife for changing or other purposes
at the 3:00 position of the disc. According to the invention, then, the opening
in the shroud is preferably situated at this position. Moreover, providing the
interlocking features of the knife and outer clamping member in combination with
the interlocking features of the knife and counterknife provides for safely holding
the knife in the apparatus as well as indexing the knife to the apparatus in either
or both the 9:00 and 3:00 positions of the disc, resulting in outstanding flexibility.
It is to be recognized that, while a specific method and apparatus for clamping
a knife has been shown and described as preferred, other configurations could be
utilized, in addition to configurations already mentioned, without departing from
the principles of the invention.
The terms and expressions which have been employed in the foregoing specification
are used therein as terms of description and not of limitation, and there is no
intention in the use of such terms and expressions to exclude equivalents of the
features shown and described or portions thereof, it being recognized that the
scope of the invention is defined and limited only by the claims which follow.
*
