Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
This invention relates to th~ field of
metalcutting tools, and more specifically, to milling
cutters.
In those types of milling cutters having
indexable inserts, each insert is clamped into a pocket
of the cutter body by a wedge clamp, several of which
are well known in the prior art. Most of the inserts
so used in milling cutters are made from cemented
carbide material.
During the manufacture of the milling cutter,
and more particularly, the machining of the insert
pockets and clamp recesses as well as the clamp itself,
various tolerances are created. The more surfaces that
are machined, the more tolerances that are created.
While mor~ tolerances may cancel each other out, other
tolerances may add together so as to result in a
cumulative tolerance.
When the insert is placed in the insert
pocket and the wedge applied, this cumulative tolerance
may prevent the wedge face from making planar contact
with the insert. Instead, the wedge may meet the
insert along a line, or perhaps even at a point. With
cemented carbide inserts, thi~ nonplanar contact is not
a problem since cemented carbides have a certain amount
of toughness which allows them to withstand nonplanar
contact.
On the other hand, if ceramic inserts are
used, as is of ten the case today, a serious problem is
encountered. Ceramic inserts are extremely brittle.
If there is nonplanar contact between the wedge face
and the insert, as is possible with conventional
clamping means, the insert may crack.
It would, of course, be desirable to be able
to clamp a ceramic insert without causing it to crack.
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It is thus an object of this invention to
have a means of clamping a ceramic insert without
causing it to crack.
It is another object to have a clamp in which
there is always planar contact between a surface of the
clamp and the insert.
It is a further object to have a clamp that
is simple to use and manufacture as well as economical
to buy.
lo It is a still further object of this
invention to have a clamp that is usable with camented
carbide inserts as well as ceramic inserts.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, there is
a milling cutter comprising a cutter body rotatable
about its central axis, a peripheral wall on the cutter
body and insert pockets and clamp recesses located in
the peripheral wall. The insert pockets have locating
surfaces for positioninq an insert when placed in the
pocket. There is also clamp means for releasably
clamping an insert when the insert is placed and
positionecl in the pocket. The clamp means freely
assumes an orientation identical to that of the insert
so that planar contact is made with the insert.
The clamp means has a first planar surface
for abutting engagement with an insert and a movement
means for advancing and retracting the first planar
surface from abutting engagement with the insert. The
first planar surface has a preselected limited pivotal
movement in all directions about the axis of the
movement m~ans when in an unclamped position.
The clamp recess has a clamp contact surface
and the movement means has a bearing surface located
about its axis. The bearing surface and the first
planar surface cooperate through a wedging action
transmitting surface so that as the bearing surface
abuts the clamp contact surface the first planar
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surface pivots to conform to the surface orientation of
the insert. Preferably, the bearing surface is convex.
The clamp means further comprises a second
planar surface opposite the first planar surface. The
first and second planar surfaces are rigidly associated
with each other and are also associated with a C-shaped
perforation within which the bearing surface is
rotatably movabl~. The perforation communicates with
the second planar surface. The bearing surface has a
portion protruding beyond the perforation and beyond
the second planar surface. The bearing surface portion
abuts the clamp contact surface when in a clamped
position.
More pref~rably, thP clamp means further
comprises a retaining ring on the movement means so
that the movement means is captively held in the
perforation.
The milling cutter further comprises a shim
located rearward in the rotational sense of the insert
and is interposed between the insert and the insert
pocket. Preferably, the insert is a hard w~ar
resistant ceramic material.
In another preferred embodiment, the bearing
surface is planar and the retaining ring is
perpendicular to the bearing surface so that the
bearing surface ls captively held by the perforation.
According to the invention, disclosed is a
clamp means for clamping an insert to a cutter body.
The clamp means comprises a wedge and a movement means
cooperating with the wedge. The wedge has a top and
bottom joined together on one side by a first planar
surface. The first planar surface has a preselected
limited pivotal movement in all directions about the
axis of the movement means.
Preferably, the movement means has a
bearing surface located about its axis. In one
preferred embodiment, the bearing surface is convex.
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Preferably, also, the wedge has a second planar
surface joining the top and bottom on the
opposite side from the first planar surface. Th~
wedge also has a C-shaped perforation between the
top and bottom surface and communicating with the
second planar surface. The bearing surface is
rotatably movable within the perforation and beyond the
second planar surface.
More preferably, the wedge perforation has a
lo lip where the perforation intersects the bottom and the
movement means has a retaining ring. The movement
means is captively held in the perforation by the
retaining ring interacting with the lip.
According to one aspect, the present
invention relates to a milling cutter comprising a
rotatable cutter body having a clamp contact surface
and an insert locating surface, and a clamp adapted to
provide a substantially completely contacting action
over the face of said cutting insert comprising a one
piece wedge having a first bearing surface for
contactinc3 said face of said cutting insert and thereby
clamping said cutting insert between said first bearing
surface and said insert locating surface provided in
said pocket, movement means for moving said wedge
relative to said cutter body, a second hearing surface
provided on said movement means for contacting said
clamp contact surface provided in said pocket, and a
gap provided between said one piece wedge and said
movement means such that said first and second bearing
surfaces are at least rotatable relative to one another
in at least two separate directions.
According to a further aspect, the invention
relates to a method of assembling a milling cutter,
~aid milling cutter comprising a rotatable cutter body
having a peripheral wall, said peripheral wall being
provided with an insert pocXet for accepting a cutting
insert, said insert pocket having a clamp contact
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surface and an insert locating surface, said method
comprising the steps of placing a cutting insert into
said insert pocket and accurately positioning said
cutting insert with respect to said locating surface,
placing a clamp into said pocket, said clamp comprising
a one piece wedge having a first bearing surface for
contacting a face of said cutting surface and thereby
clamping said cutting insert between said first bearing
surface and said insert locating surface provided in
said pocket, movement means for moving said wedge
relative to said cutter body, a second bearing surface
provided on said movement means for contacting said
clamp contact surface provided in said pocket, and a
gap provided between said one piece wedge and said
movement means such that said first and second bearing
surfaces are at least rotatable relative one another in
at least two separate directions, and advancing said
movement means so as to align said first bearing
surface with the face of said cutting surface and such
that said second bearing surface abuts said clamp
contact surface and said cutting insert is clamped
between said first bearing surface and said insert
locating surface.
BRIEF DESCRIPTION OF THE DRAWINGS
The exact nature of the present invention
will become more clearly apparent upon reference to the
~ollowing detailed specification taken in connection
with the accompanying drawings in which:
Figure l is a plan view of the milling cutter
according to the invention.
Figure 2 is a side view of the milling cutter
of Fiqure 1.
Figure 3 is a plan view of the cutter body
with associated hardware removed.
Figure 4 is a side view of the cutter body of
Figure 3.
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Figure 5 is a sectional view of the milling
cutter according to the invention along the line V-V of
Figure 3.
Figure 6 is an end view of the clamp means of
Figure 5.
Figure 7 is a sectional view showing planar
contact between an insert and a clamping surface.
Figure 8 is a sectional view showing
nonplanar contact between an insert and a clamping
lo surface.
Figure 9 is a sectional view similar to
Figure 5 showing another embodiment of the clamp means.
Figure 10 is an end view of tha clamp means
of Figure 9.
Figure 11 is a sectional view similar to
Figure 5 but showing a further embodiment of the clamp
means.
Figure 12 is an end view of the clamp means
of Figure 11.
Figure 13 is a sectional view similar to
Figure 5 but showing a still further embodiment of the
clamp means.
Figure 14 is an end view of the clamp means
o~ Figure 13.
Figure 15 is a view of Figure 14 in the
direction of arrow XV.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings somewhat more in
detail, Figures 1 and 2 show the assembled milling
cutter 2. There is a cutter body 4 having a direction
of rotation 6, a peripheral wall 8, clamp means 10 and
insert 12.
Figures 3 and 4 show the cutter body by
itself without the associated hardware. ~hown is a
chip gash portion 18, an insert pocket 19 and clamp
recess 26.
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As can be seen in Figures 1 through 4, there
is only one station shown~ A station comprises a
cutter body along with its associated hardware, such as
clamp means and inserts. While only one station is
shown, it is understood that a milling cutter typically
comprises several such stations.
Referring now to Figures 1 through 4
together, disclosed according to ~he invention is a
milling cutter. The milling cutter 2 comprises a
cutter body 4, rotatable in the direction of rotation 6
about its central axisr There is a peripheral wall 8
on the cutter body 4 and insert pockets 19 and clamp
recesses 26 located in the peripheral wall 8. The
insert pockets have locating surfaces 24 for
positioning an insert 12 when placed in the pocket 19.
There is clamp means 10 for releasably clamping an
insert 12 when the insert is placed and positioned in
the pocket 19. The clamp means 10 freely assumes an
orientation identical to that of the insert so that
planar contact is made with the insert.
Referring now to Figures 5 and 6, the clamp
means 10 has a first planar surface 30 for abutting
engagement with an insert 12. There is a movement
means 32 for advancing and retracting the first planar
surface 30 from abutting engagement with the insert.
The first planar surface 30 has a preselected limited
pivotal movement in all directions about the axis 34 of
the movement means when in an unclamped position.
The advantages of this invention can best be
seen by referring to Figures 7 and 8. Figure 7 shows
the first planar surface meeting the insert according
to this invention. It is obvious that the first planar
surface and the insert are making complete planar
contact. Figure 8 shows contact that is achieved
according to the prior art. In the prior art clamping
means, there would possibly be line or point contact,
as shown, for example, at 40. Such line or point
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contact would be disastrous to ceramic inserts as it
would likely cause the insert to crack.
Cemented carbide inserts can survive the
nonplanar contact due to their greater toughness;
however, the nonplanar contact may cause th~ insert to
tilt slightly within its pocket, which can have an
adverse effect on insert life. It is apparent, then,
that applicants' invention could be advantageously
applied to cemented carbide inserts as well as ceramic
insertS-
Referring back to Figures 5 and 6, the clamp
recess 26 has a clamp contact surface 28 and the
movement means 32 has a bearing surface 42 located
about its axis 34. The bearing surface 42 and the
first planar surface 30 cooperate through wedging
action transmitting surface 43 so that as the bearing
surface abuts the clamp contact surface 28, the first
planar surface 30 pivots to conform to the surface
orientation of the insert 12.
The clamp means further comprises a second
planar surface 44 opposite the first planar surface.
The first and second planar surfaces are rigidly
associated with each other and are also associated with
a C-shaped perforation 46 within which the bearing
surface 42 is rotatably movable. The perforation
communicates with the second planar surface 44. The
bearing surface has a portion 48 protruding beyond the
perforation and beyond the second planar surface. The
bearing surface portion 48 abuts the clamp contact
surface 28 when in a clamped position.
In a preferred embodiment, the bearing
surface is convex.
In order to achieve the objects of the
invention, it is necessary to avoid all contact between
the second planar surface 44 and both the clamp contact
surface 28 and the top wall 29 of the clamp recess.
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Preferably, the clamp means further comprises
a retaining ring 50 on movement means 32 so that the
movement means is captively held in the perforation 46.
The movement means is typically threaded 25 into the
back wall 27 of the clamp recess.
The milling cutter further comprises a shim
14 located rearwardly, in the rotational sense, o~ the
insert 12 and is interposed between the insert and the
insert pocket 19.
The insert pocket may also have shim locating
position 22 and bottom wall 20. As can be seen in
Figures 1 and 2, the milling cutter may also have a
nest 16 and a second clamp means 11D The second clamp
msans is used solely for clamping the next.
Preferably, the insert 12 is a hard wear
resistant ceramic material. However, other inserts are
contemplated within the scope of the invention. Such
other inserts may be cemented carbide inserts as are
well known in the art.
Referring back to Figures 5 and 6, according
to the invention, there is clamp means 10 for clamping
insert 12 to a cutter body 4. The clamp means
comprises a wedge 52 and a movement means 32
cooperating with the wedge. The wedge has a top 54 and
a bottom 56 joined together on one side by a first
planar surface 30. The first planar surface has a
preselected limited pivotal movement in all directions
about the axis 34 of the movement means.
The movement means has a bearing surface 4~
located about its axis 34. The wedge 52 has a second
planar surface 44 joining the top 54 and the bottom 56
on the opposite side from the first planar surface.
The wedge also has a C-shaped perforation 46 between
the top 54 and bottom 56 and communicating with the
second planar surface 44. The bearing surface 42 is
rotatably movable within the perforation and has a
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portion 48 protruding beyond the perforation and beyond
th~ second planar surface.
In a preferred embodim nt, the bearing
surface is convex.
Preferably, the wedge perforation 46 has a
lip 58 where the perforation 46 intersects the bottom
56 and the movement maans has a retaining ring 50. The
movement means is captively held in the perforation by
the retaining ring interacting with the lip.
Referring now to Figures 9 and 10, shown is a
modified clamp means 10'. The modification principally
lies in the head 60 of the movement means wherein the
head is slightly recessed. Notwithstanding this
modification, the bearing surface 42 and the first
planar surface 30 cooperate through wedging action
transmitting surface 43, as before, so that as the
bearing surface abuts the clamp contact surface 28, the
first planar surface 30 pivots to conform to the
surface orientation of the insert 12.
While it is preferred to have the clamp means
forward, :in the rotational sense of the insert, it is
also contemplated within the scope of the invention to
have the clamp means rearward of the insert, as is
shown in Figures 11 and 12. Bearing surface 42 of
modified clamp means 10'' has a portion which abuts
clamp contact surface 28 when in a clamped position.
Wedging action transmitting surface 43 is located
slightly differently but, nevertheless, cooperates in a
similar manner with first planar surface 30 and bearing
surface 42.
A further modification of the milling cutter
and clamping means is illustrated in Figures 13, 14 and
15. The milling cutt~r body 4 has clamp means 10l''.
The clamp means 10" ' has a first planar surface 30 for
abutting engagement with an insert 12. There is a
movement means 70 for advancing and retracting the
first planar surfac~ 30 from abutting engagement with
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the insert. The first planar surface 30 has a
preselected limited pivotal movement in all directions
about the axis 34 of the movement means when in an
unclamped position.
The clamp recess 26 has a clamp contact
surface 28 and the movement means 70 has a bearing
surface ~2 located about its axis 34.
In the other embodiments of this invention,
the movement means and the bearing surface would
normally be located on the same member. In contrast to
these ~mbodiments, the movement means 70 and the
bearing surface 72 in the Figure 13, 14 and 15
embodiments are now on separate members.
Preferably, the movement means 70 is now a
double-ended oppositely threaded fastener.
The bearing surface 72 is now located on
bushing 74. The bushing 74 has a diametrical portion
76 and a conical portion 78. Extendîng longitudinally
of the bushing and on its periphery is a planar
portion, ~he bearing surface 72. The bushing also has
a perforation 80 for threadedly engaging the movement
means 70.
The bushing is rotatably mounted in the C-
shaped perforation 46 of the wedge 52. Preferably,
there is a retaining ring 50 perpendicular to the
bearing surface 72 so that the bearing surface is
captively held by the perforation.
In the assembly of the clamp means in the
clamp recess, the movement means is threadedly engaged
with the bushing. The bushing is then rotatably
mounted in the C-shaped perforation of the wedge and is
captively held there by the retaining ring 50. When
threadedly engaging the movement means with the back
wall 27 of the clamp recess, it is necessary to insure
that the bearing surface 72 faces the clamp contact
surface 28. As the bearing surface 72 is rotatable
within perforation 46 as well as around axis 34, it is
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possible that bearing surface 72 will not face clamp
contact surface 28. If the bearing surface does not
face the clamp contact surface, improper clamping will
result; hence, the necessity for properly situating the
bearing surface.
The bearing surface 72 and tha first planar
surface 30 cooperate through wedging action
transmitting surface 43 and conical portion 78 so that
as the bearing surface abuts the clamp contact surface
28, the first planar surface 30 pivots to conform to
the surface orientation of the insert 12. Since the
bearing surface is planar in this embodiment, the clamp
contact surface should be planar as well.
In order to achieve the objects of the
invention, it is necessary to avoid all contact between
the second planar surface 44 and both the clamp contact
surface 28 and the top wall 29 of the clamp recess.
This contact is avoided by having the bearing surface
72 protrude beyond the perforation and beyond the
second planar surface.
According to the invention, there is a method
of assembling a milling cutter of the type having
inserts, insert pockets, clamp recesses and locating
surfaces for positioning the inserts.
The method comprises placing an insert 12
into an insert pocket 19 and accurately positioning the
insert with respect to a locating surface 24. The next
step is placing a wedge 52 having a first planar
surface 30, cooperating movement means 32 and a bearing
surface (42 or 72) into the clamp recess so that the
first planar surface rests against the insert. A
further step is advancing the movement means so that
the first planar sureace pivots and freely assumes an
orientation identical to that of the insert so that
planar contact is made with the insert. The method
further comprises tightening the movement means so that
the bearing surface (42 or 72) moves into abutting
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engagement with a clamp contact surface 28 in the clamp
recess 26. The final step of the process comprises
repeating each st~p a number of times corresponding to
the number of insert pockets.
A milling cutter station typically comprises
a cutter body and associated hardware such as inserts,
clamps, shims and the like. As shown in the figures,
there is only one statîon. However, it is understood
that in the milling cutters with which this invention
is most conc~rned, there will be several such stations.
Modifications may be made within the scope of
the appended claims.
