PLANING CUTTER

FERS ROTATIFS DE RABOT

English Abstract

The invention is a planing cutter with a cylindrical cutter body (1) with
recesses (3) along its enveloping surface. Each recess is delimited by a front
wall (4) a rear wall (5) and a bottom (6) and contains a cutting element (7).
Each cutting element (7) has a cutting edge (8), a lower edge (9), two lateral
edges (10, 11), a front face (12) and a rear face (13). One clamping device
(2) is also located in each recess. According to the invention each lateral
edge (10, 11) of the cutting element (7) has a range (14) of grooves. At least
one groove in each range interacts with a peg (17, 18) protruding from one of
the walls (4, 5) of the recess (3). The invention also concerns a cutting
element (7) for use with the cutter of the invention.

French Abstract

L'invention concerne un fer rotatif de rabot comprenant un corps fer rotatif (1) cylindrique dont la surface extérieure est pourvue d'évidements (3). Chaque évidement, délimité par une paroi avant (4), une paroi arrière (5) et un fond (6), abrite un élément coupant (7). Chaque élément coupant (7) présente une arête coupante (8), un bord inférieur (9), deux bords latéraux (10, 11), une face avant (12) et une face arrière (13). Un dispositif de fixation (2) est également placé dans chaque évidement. Selon l'invention, chaque bord latéral (10, 11) de l'élément coupant (7) présente un ensemble (14) de rainures. Au moins une rainure de chaque ensemble est en prise avec un tenon (17, 18) en saillie à partir d'une paroi (4, 5) de l'évidement (3). L'invention concerne également un élément coupant (7) conçu pour être utilisé dans le fer rotatif de rabot selon l'invention.

Claims

7
CLAIMS
1. A planing cutter comprising: a cylindrical cutter body having an outer
surface
formed with a plurality of recesses therein, said recesses delimited by a
front wall, a
rear wall and a bottom, each recess containing a cutting element with a
cutting edge
having two axial ends, a lower edge, two lateral edges, a front face and a
rear side,
said recess also containing a clamping device, each lateral edge of the
cutting
element having a range of grooves, and at least one groove in each range
interacting
with a peg projecting from one wall of the recess, and by the number of
grooves in
each range engaging the peg being less than the total number of grooves in the
range the axial length of the cutting edge being smaller than the axial width
of the
cutter body, each lateral edge extending from the corresponding end of the
cutting
edge along a line perpendicular to the cutting edge.
2. The planing cutter according to claim 1, wherein two of the grooves in each
range engage with each one peg projecting from the wall.
3. The planing cutter according to claim 1, wherein each peg has a circular
section.
4. The planing cutter according to claim 1, wherein each groove has a circular
arc section.
5. The planing cutter according to claim 1, wherein each peg is attached to
the wall
by having one end portion inserted in a hole drilled in the wall.
6. The planing cutter according to claim 1, wherein the clamping device
comprises an
element in contact with one face of the cutting element and covering both
ranges of
grooves.

Description

CA 02420223 2008-09-16
PLANING CUTTER
Field of the Invention
This invention relates to a planar cutter for planning wood, and in particular
to
a cuffing element.
Backaround of the Invention
A planing cutter should preferably have a relatively large number of seats
with
cutting elements for simultaneous planning of upper, lower and lateral faces
of a
board. A large number of cutting elements allows larger cutting capacity,
better
surface smoothness of the planed faces and lower noise level. On a cutter with
160
mm diameter there are normally seats for six cutting elements. Clamping and
locking
of the elements is an important aspect here. Of course, it must be safe, it
must be
simple and it should have small peripheral dimension. The number of cutting
elements to be applied to a planing cutter is normally limited by the
peripheral space
needed for the clamping mechanism.
It is especially desirable to allow high rotational velocity of the cutter, if
possible to reach velocities around 10-12 000 rpm. At such velocities the
stability
and safety of the clamping has a decisive importance. When centrifugal forces
are
as great as in this velocity region, there is a tendency for the cutting
elements of the
cutter to move radially outward. The clamping must be such that this is
prevented or
at least reduced to an acceptable level even at such high velocities. The
clamping
position of the cutting elements should also be radially adjustable to allow
regrinding
of the edges.
Conventionally, each cutting element is located in a recessed seat in the
cutter and clamped against one of the walls of the recess. Such a clamping
constitutes a force defined connection, where the defining force is a
frictional force.
To make the clamping safer, it is previously known to supplement it with a
shape
defined connection.
Examples of such clamping of the cutting elements to the body of a cutter are
described in EP 455 196, WO 94/07665, DE 3701053 and CA 2135146.
EP 455 196 shows in figure 1 how a cutting element is clamped to a recess in
the body of the cutter by a clamping wedge. The cutting element is further
locked by
a peg located in one wall of the recess and penetrating through a hole in the
element.
The cutting element is then not adjustable in the radial direction.
Furthermore, this

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2
type of clamping has the disadvantage of requiring providing of a hole through
the
cutting element, which reduces its strength and increases its cost of
manufacture.
WO 94/07665 describes a clamping device with a positioning device for the
cutting element. One wall of the recess is furthermore provided with
serrations
matching serrations on one wall of the cutting element. The cutting element
can be
radially relocated and placed in a new operative position where the serrations
match
again. Since this device requires that the wall of the recess as well as one
side of
the element are provided with serrations, it will be complicated and costly
from a
manufacturing viewpoint.
DE 3701053 describes a device which in principle corresponds to the above,
and also suffers from the same disadvantages.
CA 2135146 describes a device where the cutting element is clamped by a
tensioning element. Furthermore, one side of the cutting element is provided
with a
groove interacting with a groove in a support plate rigidly attached to the
cutter body.
The interaction is by means of a locking element protruding into the grooves
of the
cutting element as well as the support plate. This locks the cutter element to
the
recess by a shape connection. The support plate has a number of grooves to let
the
locking element interact with an arbitrary groove of the support plate. In
this way the
radial position of the cutting element can be adjusted. This device must also
be
regarded as complicated to manufacture, since the cutting element must be
provided
with a groove, and the support plat with a number of grooves.
Summary of the Invention
In relation to this background, the purpose of the present invention is to
provide a planing cutter which in a simpler way than previously known will
allow a
stable and safe clamping of the cutting element, even at high rotational
velocities,
and which will permit adjustment of the radial position of the cuffing
element.
According to the invention, this purpose is achieved when a planing cutter is
provided
with the special features to be described.
Due to interaction between a groove in the cutting element and a peg
projecting from the wall of the recess, a safe shape defined locking of the
cutting
element is achieved, capable of resisting high rotational velocities without
noticeable
outward displacement of the cutting element. Since the cutting element has a
range
of grooves at each lateral edge, the radial adjustment is easily achieved.
Such
grooves at the lateral edges of the cutting element can be easily provided by
profile

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3
grinding. Provision of pegs at the wall of the recess is also easily achieved.
According to the present invention stable clamping and radial adjustability
can be
combined in a simpler and less costly way than in prior art.
Although the peg or pegs protrude from the wall of the recess, i.e. that they
may protrude directly from the wall, it will be understood that the pegs can
protrude
from a separate element rigidly connected to the wall, such as a plate
adjoining and
attached to the wall by screws.
According to one preferred embodiment of the invention, two grooves within
each range of grooves each interact with a peg protruding from the wall of the
recess. The provision of two pegs on each side provides improved stability and
safety of the clamping.
According to another preferred embodiment of the invention, the number of
grooves interacting with pegs is less than the total number of grooves in the
range.
This is an efficient and simple way to facilitate radial adjustment of the
cutting
element.
According to another preferred embodiment each peg has a circular cross-
section. This allows a simple mechanical design, optimal strength and simple
removal from the wall.
According to another preferred embodiment each groove has a circular arc
profile. This ensures good contact between groove and peg, to spread the force
over
a larger surface.
According to another preferred embodiment each peg is fastened to the wall
by having its end portion inserted in a drilled hole in the wall. This makes
attachment
of the peg to the wall very simple.
According to another preferred embodiment the clamping device comprises a
clamping element in contact with one face of the cutting element and covering
both
ranges of grooves. With such a clamping element the risk of loosening of the
pegs is
eliminated.
The purpose stated can according to a second aspect of the invention be
achieved with a cutting element is suitable for use in a planing cutter
according to the
invention, and will provide advantages corresponding to what was mentioned
above.
Brief Description of the Drawings

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4
The invention will be further explained by the following detail description of
a
preferred embodiment, with reference to the accompanying figures.
Figure 1 shows a radial section through a part of a planing cutter according
to
the invention.
Figure 2 is an axial section along the line II - II of Figure 1.
Figure 3 is an enlarged section corresponding to figure 1 and shows the
cutting
element in a second position.
Detailed Description of the Preferred Embodiment
In Figure 1 is shown a radial section of a planing cutter according to the
invention. The cutter comprises a cutter body 1 arranged to rotate in the
direction of
arrow A when planing. In the enveloping surface of the body 1 is located a
number
of recesses 3, in the example shown twelve such recesses. In each recess is
located one cutting element 7 and one clamping device 2. In front of each
cutting
element there is a chip-breaker 23 made as a arcuate ditch. The clamping
device 2
comprises a wedge-shaped body 21 and a clamping screw 22. Their function will
be
further described below in connection with Figure 3. The wedge-shaped body
keeps
the cutting element 7 pressed against the front wall 4 of the recess, locking
the
element between the wedge-shape body 21 and the wall 4.
The cutting element is laterally limited by two lateral edges, and in each of
those a range of grooves 14 is provided. In the front wall 4 of the recess 3
are
provided holes 19,20, and in each of those a peg 17,18 is located, protruding
from
the wall 4. Each peg 17,18 interacts with one groove each 15,16 in the range
of
grooves.
Figure 2 which is a section along the line II - II in Figure 1 further
explains the
shape of the cutting element 7. The figure shows the rear face 13 of the
cutting
element 7, the face oriented to the rear relative to the direction of
rotation. At the
upper part of the figure is the cutting edge 8 and in the bottom part the
lower edge 9.
This figure clearly shows how each lateral edge 10,11 of the cutting element
is
provided with a range of grooves 14a, 14b. In the example shown there are
twelve
such grooves located at each lateral edge, each with a semicircular profile.
The

CA 02420223 2008-09-16
number of grooves may of course be different, and the profile may be
otherwise. The
profile may be V-shaped for instance.
In Figure 2 is also indicated the front wall 4 of the recess in the cutter
body.
As shown the recess is somewhat broader than the length of the cutting element
7, to
5 let an outer part of the front wall 4 extend a few mm past each lateral edge
10,11.
From the wall 4 the two pegs 17a, 18a, 17b, 18b extend at each lateral edge at
right
angle to the plane of the figure. The pegs are shown as cylindrical tubes. By
these
pegs 17a, 18a, 17b, 18b interacting with the corresponding grooves the cutting
element is locked without possibility to move.
The cutting element 7 is shown in Figures 1 and 2 as new, without having
been re-sharpened, and its lower edge is then close to the bottom of the
recess.
One common size of a cutting element as in the example shown is 106×35
mm.
The grooves in the range of grooves 14a, 14b may have a radius of 1 mm. The
pegs
17a, 18a, 17b, 18b may then have a diameter of 2 mm and a total length of 10,3
mm.
The centre distance between adjacent pegs 17a, 18a on one side may be 4 mm.
In Figure 3 which is similar to Figure 1 but in enlarged scale the cutting
element is shown in its radially outermost position, where the inner peg 18
interacts
with the innermost groove. This figure shows that a clamping element 21 covers
the
openings of the grooves at the rear face 13 of the cutting element. The
clamping
element 21 has a width corresponding to the breadth of the recess. The
clamping
element 21 is wedge-shaped and the recess 3 also has a corresponding wedge
shape section. The clamping element is loosened or tightened with one or more
clamping screws 22. By screwing them inward the clamping element 21 is pressed
upward to contact against the rear wall 5 of the recess 3 and against the rear
side 13
of the cutting element 7, thereby locking the cutting element 7 between the
clamping
element 21 and the front wall 4 of the recess.
When a new cutting element as shown in Figures 1 and 2 becomes worn and
blunt, the cutting element is released by loosening the clamping screws 22.
The
clamping element 21 can the be moved down into the recess where it becomes
loose
and can be pulled out axially from the cutter. The cutting element 7 can then
be
removed from the position shown in Figure 1 to be re-sharpened. The cutting
element is then ground off an amount corresponding to the centre distance
between
two grooves. The cutting element is then replaced between the pegs, but now
radially displaced so far that each peg interacts with a groove located
radially nearest
below the groove it formerly interacted with. After replacing and re-
tensioning of the

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clamping element 21, the cutter is again ready for planing. Re-sharpening and
adjusting can be made several times until finally the innermost of the grooves
is used
for interaction with a peg as shown in Figure 3.
It should be obvious that all dimensions mentioned above are only to be
interpreted as examples.

Representative Drawing