Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
21 6~B~
.
The present invention relates to the field of sawmill
equipment, and provides a novel knife and counter knife
combination for use with wood chipping apparatus. The present
invention also provides a modified clamp for holding the knife
in place against the counter knife, and a novel device for
permitting the knife on a chipping machine or the like to be
angled over a range of angles.
In this specification, reference will be made to chipping
r-~h i nPc including disk chippers, drum chippers, chipper
canters, chipper slabbers, chipper edgers, or chipper reman
(remanufacturing) machines. It will be understood that these
machines each utilize essentially the same type of knife, so
no distinction will be made between them, and the present
invention will be understood as extending to each of the
foregoing ~--h;n~, and any other machinery utili7;n~ the same
or similar knives.
Now, using a disk chipper as an example, the chipper
comprises a monolithic massive steel disk into which pockets
are formed on the outer surface. Each pocket extends radially
from near the centre to near the perimeter of the disk, and
includes a knife holder bolted into the pocket over a thin
plate known as a control plate, a counter knife bolted onto the
knife holder, a clamping plate over the knife holder, and
between the clamping plate and the counter knife, a knife keyed
--1--
216~22
to the counter knife and forcibly held on the counter knife by
the clamping plate. This form of system, that is generally
considered the industry standard is shown for instance, in U.S.
Patent No. 4,997,018. The knife is fairly compact, double
edged, with hardened edges. Unlike conventional chipper knife
designs that utilized a massive knife equivalent to the
clamping plate and knife of the above described system, the
knife of the above described system is not considered re-
grindable. It has a hardened edge for long life and can be
honed, but is not of sufficient size or thickness for re-
grinding involving stock removal to change the profile thereof.
It is sometimes necessary to change the angle of the knife
blade to the surface of the disk. This is usually from 29 -
31, for most softwoods and hardwoods, but for harder woods,
such as very knotty wood, dry hardwood, or frozen wood, angles
of up to about 35 or 36 are desired. To change the angle of
the knife blade in a conventional solid blade system, the back
surface of the blade is ground down, from about 1 to about 5O~
as required. This provides a correctly angled blade, but uses
2 0 up valuable stock on the blade . In the system described in
U.S. Patent No. 4,997,018, referred to above, control plates
having wedge shaped profiles are utilized, to angle the blade
holder assembly resting on the control plate. Therefore,
changing the angle of the blade holder requires substantially
complete ~ pmhly of the pocket assembly, and use of a
--2--
21 6~B22
specialized, expensive, thin, wedge-shaped part. Moreover,
since the blade holder will then be at an angle to the bottom
surface pocket, the tapped hole in the blade holder will be at
a slight angle to the bolt ~Yt~nr~; ng from through the disk.
When that bolt is torqued down, then, its head will not seat
perfectly flatly against the back of the disk. This may create
problems in tightening the blade holder securely in the pocket.
The object of the present invention, therefore, is to
provide a knife for a system compatible with the knife holders
of the system shown in U.S. Patent No. 4,997,018, which knife
can be angled at from about 29 to about 36 from the face of
a disk without the need to change for knives of different
angles or to use a wedge-shaped control plate located under the
knife holder to control the infeed force of the knife or
lliF~i'lFF' ~,le all components in the pocket of the disk.
In order to accomplish the foregoing object, the present
invention provides a novel knife and counter knife
combination, preferably for use with a modified clamp, as will
be described. Also provided are novel spacers for effecting
angulation between the knife and counter knife.
In a broad aspect, then, the present invention relates to
a knife and counter knife for a chipping machine that is
provided with a knife holder having means for fixing said
--3--
216~622
counter knife in place, and a clamping plate for clamping said
knife firmly against said counter knife, characterized in that
said counter knife has a leading edge profiled to permit
rotation of said knife, the bottom surface of said knife being
complementarily prof iled to rotate about the leading edge of
said counter knife.
In drawings that illustrate the present invention by way
of example:
Figure 1 is a cross-sectional view through a knif e blade
of a first PrhQrl;r-nt of the present invention, mounted in a
knife holder; and
Figure 2 is a cross-sectional view through a knife blade
of a second ~ nt of the invention.
Referring now to Figure 1, a knife holder 4, for insertion
into, e.g., the knife pocket of a chipper disk, is shown
Pqll;rpPd with the knife of the present invention. The knife
holder 4 is provided at its forward upper edge with a counter
knife 2, the forward edge of which has a semi-circular
pro~ection 21 extending its length. Just behind the projection
21 is a groove 9 which may, for instance, be a shallow squared
groove, as shown in the drawings.
The knife 1 of the present invention is provided with a
pair of symmetrically disposed;emi-circular grooves 11 on its
~ 2l~n~2~
under surface. Each of these grooves is dimensioned to provide
a close fit with semi-circular projection 21 on the counter
knife. Therefore, with the knife 1 mounted on the counter
knife 2, the knife 1 can rotate forwardly, as shown in Figure
1. In the figure, the knife 1 shown in solid lines is set at
35 to the face of the disk, the angle of which is shown as a
horizontal line above the figure. The actual face of the disk
would, of course be below the cutting edge of the knife.
Maintaining the knifQ at a 35 angle is a spacer rod 7 inserted
in shallow square groove 9 in the counter knife 2, extending
into the rearward groove 11 of the knife 1. As will be seen
in Figure 1, the lowermost surface of rod 7 is machined way to
form a smooth flat surface, and to provide the rod with a
precise width, whereby the angle setting of the knife can be
reliably duplicated. In order to provide a wide range of
possible angular settings of the knife, a number of rods, e.g.,
one for each degree or half degree between 29 and 35 is
provided. shown in Figure 1 is a second angular setting, 30
of the knife, la, in phantom. It will be seen that the
rearward groove 11 on the knife is lifted, and the space for
rod 7 is wider. A different rod would, therefore, be inserted
and the clamp bolt 6 tightened, to tighten clamp 5 against the
knife 1. As shown in Figure 1, the forward edge of clamp 5
will be shortened, to ensure that clamping pressure, without
creating a gap between the forward edge of the clamp and the
knife 1 is exerted on the top surface of the knife 1, between
2150622
the grooves on the lower surface thereof. This ensures that
the clamping pressure does not act to rotate the knife 1.
Referring now to Flgure 2, an alternative form of the
present invention is disclosed. In this form, the spacer rod
7 is replaced with a spacer wedge 8 having a head 81, and a
wedge-shaped tail 82. The tail 82 is provided with apertures
for set screws 83 to secure the tails to the counter knife.
The head 81 and tail 82 are dimensioned to provide the
angulation of knife 1 desired. As is the case with rods 7 for
the form of invention shown in Figure 1, the spacer wedges 8
are provided in sets of incremental angles, an entire set
permitting a user to set the blade of a chipper at any desired
angle. Preferably, the angle setting associated with a spacer
rod 7 or wedge 8 is stamped on it, permanently.
It will be understood that the knife of the present
invention is double edged, with back grind bevels under each
edge, so it can be reversed for usage of each edge before re-
honing .
It is to be understood that the examples described above
are not meant to limit the scope of the present invention. It
is expected that nl~l uus variants will be obvious to the
person skilled in the f ield of wood chipping equipment design
without any departure from the spirit of the invention. The
--6--
21~622
appended claims, properly con6trued, form the only limitation
upon the scope of the invention.
