U.S. patent application number 14/633563 was filed with the patent office on 2015-06-25 for holder for a cutting tool, a cutting tool and a cutting insert.
The applicant listed for this patent is GKN Aerospace Sweden AB. Invention is credited to Tore Hagward, Anders Wretland.
Application Number | 20150174665 14/633563 |
Document ID | / |
Family ID | 41377826 |
Filed Date | 2015-06-25 |
United States Patent
Application |
20150174665 |
Kind Code |
A1 |
Wretland; Anders ; et
al. |
June 25, 2015 |
HOLDER FOR A CUTTING TOOL, A CUTTING TOOL AND A CUTTING INSERT
Abstract
A holder for a cutting tool, comprising a body having a first
channel for receiving a stein portion of the cutting tool. The body
has a second channel intersecting with said first channel. The
holder further comprises a plunger (13) to be inserted in the
second channel, said plunger (13) having a third channel (14) the
cross section of which at least partly overlaps with the cross
section of the first channel when the plunger (13) is inserted into
the body so as to enable the stem of the cutting tool to extend
into the third channel (14) when the stem is inserted in the first
channel. The holder (1) further comprises a mechanism (26) for
locking the stem against movement relative to the body by means of
the plunger. The invention furthermore relates to a cutting tool
for use in such a holder and a cutting insert.
Inventors: |
Wretland; Anders; (Vastra
Frolunda, SE) ; Hagward; Tore; (Trollhattan,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GKN Aerospace Sweden AB |
Trollhattan |
|
SE |
|
|
Family ID: |
41377826 |
Appl. No.: |
14/633563 |
Filed: |
February 27, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13321860 |
Nov 22, 2011 |
8992139 |
|
|
PCT/SE2009/000270 |
May 26, 2009 |
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14633563 |
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Current U.S.
Class: |
408/147 |
Current CPC
Class: |
B23B 27/145 20130101;
B23B 2200/201 20130101; B23B 31/305 20130101; B23B 2260/12
20130101; B23B 29/03403 20130101; B23B 2200/208 20130101; B23B
27/10 20130101; Y10T 279/1216 20150115; Y10T 408/85 20150115; Y10T
408/95 20150115; B23B 29/03407 20130101; Y10T 408/8598 20150115;
B23B 27/007 20130101; Y10T 408/94 20150115; B23B 2231/24 20130101;
B23B 2231/028 20130101 |
International
Class: |
B23B 29/034 20060101
B23B029/034 |
Claims
1. A holder for a cutting tool, comprising a body having a first
channel for receiving a stem of the cutting tool, characterized in
that the body has a second channel intersecting with said first
channel, the holder further comprises a plunger having a third
channel the cross section of which at least partly overlaps with
the cross section of the first channel when the plunger is inserted
into the body so as to enable the stem of the cutting tool to
extend into the third channel when the stem of the cutting tool to
extend into the third channel when the stem is inserted in the
first channel, and that the holder further comprises a mechanism
for locking the stem against movement relative to the body by means
of the plunger.
2-24. (canceled)
Description
FIELD OF INVENTION
[0001] The invention relates to a holder for a cutting tool
according to the preamble of claim 1. In particular the invention
relates to holder for a cutting tool where the holder is adapted to
firmly hold the cutting tool to transfer a rotational movement from
a driving source in boring or milling machine to a cutting tool
secured in the holder. The cutting tool may preferably be designed
for chip forming metal cutting.
BACKGROUND OF THE INVENTION
[0002] Precision cutting requires that the position at which a
cutting tool is located when held by a holder for the cutting tool
is highly reproducible. For this purpose various types of holder
for cutting tools are known. Precision hole making is defined by
characteristics--among others--such as straightness, roundness and
position accuracy, and in addition--for some applications--the
properties of the produced surfaces. In particular for high
integrity components such as gas turbine rotors and pressurized
vessels a high demand is imposed on the tools in order to achieve
the desired property on the machined surfaces. The type of tool
holder used has an impact of the quality of the worked
surfaces.
[0003] A common type of tool holder is designed as body having a
channel for receiving a stem portion of a cutting tool. The stem
portion will be locked by screws that penetrate into the channel in
order to engage with the stem portion of the cutting tool. With
this type of locking engagement, load is concentrated to one or two
locations where the screw or screws engage with the stem. It has
shown that this type of engagement does not suppress oscillations
for certain frequencies, which frequencies depend on the location
of the connection between the screw and the shaft. Another type of
locking device is presented in U.S. Pat. No. 6,568,055, where an
axially wedge shaped sleeve is pushed by a hydraulic actuator to
tighten a boring arbour.
SUMMARY OF THE INVENTION
[0004] It is an object of the invention to provide a tool holder
that facilitates preparation of high quality surfaces and which
creates conditions for a cost-efficient production and/or use of
the tool holder.
[0005] This object is achieved by a tool holder according to claim
1. A tool holder according to the invention comprises a body having
a first channel for receiving a stem of the cutting tool. The body
furthermore includes a second channel intersecting with the first
channel. A plunger is inserted in the second channel. The plunger
has a third channel with a cross section which at least partly
overlaps with the cross section of the first channel when the
plunger is inserted into the body. The stem of the cutting tool
thereby extends into the third channel when the stem is inserted in
the first channel. The holder further comprises a mechanism for
locking the stem against movement relative to the body by means of
the plunger. The invention is based on the observation that the
quality of the machined surfaces is dependent on the wear of the
cutting insert. By virtue of the fact that the holder comprises a
plunger with said third channel, which plunger is configured for
acting on the stem, an accurate holding of the cutting tool can be
achieved. Further, by arranging the plunger moveable in the second
channel which intersects with the first channel into which a
cutting tool is inserted, lateral compensation of the position of
the cutting tool is facilitated. Hence, production of high quality
surfaces is facilitated.
[0006] According to an embodiment, the plunger comprises said
locking mechanism. In this way, the need for including functional
features for locking the cutting tool in the body is eliminated. It
is therefore easier to make the body sufficiently sturdy to achieve
a desired stiffness of the tool holder. Preferably the body may be
formed as a monolith only provided with ducts for cooling liquid
and means for locking and positioning of the plunger relatively to
the body. Hence the tool holder enables production of high quality
surfaces by facilitating lateral positioning of the cutting tool,
while allowing a compact stiff design of the body. The plunger may
thus be moveably arranged in the second channel so as to allow
lateral dislocation of the plunger and hence of the cutting tool.
Accurate lateral positioning of the cutting insert to compensate
for the successive wear of the cutting insert may therefore be
achieved in a straightforward manner while maintaining a firm grip
of the cutting tool.
[0007] According to a further embodiment, said locking mechanism
comprises a membrane delimiting a pressure chamber. The holder may
comprise a mechanism for pressurizing the pressure chamber in order
to lock the stem against movement relative to the body. In this
embodiment a holder is provided, which enables suppression of
oscillation over a wide range of frequencies.
[0008] According to a further embodiment, the membrane forms a part
of the third channel and is configured to act directly on the stem.
The pressure mechanism is configured to press the membrane directly
against the stem. Thus, the membrane is integrated into the
plunger, which creates further conditions for a firm locking of the
sutting tool.
[0009] The contact between the stem and the membrane forming part
of the third channel in the plunger ensures a distribution of the
load on the stem enabling suppressions of oscillation of the
cutting tool.
[0010] Optionally, the part of the third channel which is formed by
the membrane is cylindrical and especially circular-cylindrical.
The use of a cylindrical membrane ensures that the membrane grips
the stem with a constant radial load. A hydraulic oil pipe is
connected to the pressure chamber for enabling a movement of the
membrane thereby enabling locking or release of the stem of the
cutting tool. The use of hydraulic locking of the stem has a
beneficial effect on the suppression of oscillations of the cutting
tool.
[0011] Optionally a hydraulic oil pipe connects the pressure
chamber with an outwardly facing end wall of the plunger, at which
the mechanism for pressurizing the pressure chamber is located.
[0012] Optionally the first channel may extend along a first length
axis and the second channel may extend along a second length axis.
Each of the first and second channels are preferably straight.
Optionally the first and second axes are essentially perpendicular
to each other. By arranging the first and second axes perpendicular
to each other, the risk of that the stem is axially dislocated
during the locking process is reduced since a small movement of the
plunger in the second channel in this case will not result in a
translation of the plunger relatively to the length axis of the
first channel. Hence movement of the plunger will not result in
axial dislocation of the cutting tool.
[0013] Optionally the third channel extends through said plunger so
as to enable a stem of a cutting tool to extend through said third
channel when the stem is inserted in the first channel. The third
channel is preferably straight. By allowing the stem to pass
through the third channel a good contact between the stem and the
membrane is ascertained.
[0014] Optionally the holder includes a mechanism for movement of
the plunger along a length axis of said second channel so as to
position the stem in a lateral position relatively to the body.
Lateral positioning is performed to enable accurate positioning as
the cutting insert wears out during use.
[0015] Optionally the holder comprises means for angular and/or
axial positioning of the cutting tool relative to the body.
Preferably, the positioning means comprises an indentation provided
at an opening of the first channel, which indentation is arranged
to receive a notch provided on said stem of the cutting tool,
thereby enabling axial and angular positioning of the cutting tool.
The invention furthermore relates to a cutting tool for use in a
holder, which cutting tool includes a stem. The cutting tool
comprises means for angular and/or axial positioning of the cutting
tool relative to a body of the holder. Particularly said
positioning means comprises a notch provided on a stem of the
cutting tool, thereby enabling axial and angular positioning of the
cutting tool in the holder, The notch is to be inserted in a
corresponding indentation made at the holder for enabling axial and
angular positioning of the tool in the holder.
[0016] Optionally the stem portion of the cutting tool includes a
cooling liquid flow entrance in a lower region of the stem, a
cooling liquid feeding conduit extending from said liquid flow
entrance to a head located on the top of said stem, and a cooling
liquid ejector outlet nozzle connected to said cooling liquid
feeding conduit at said top portion of said stem.
[0017] Optionally the cooling liquid ejector outlet nozzle has a
smaller cross sectional area than said cooling liquid feeding
conduit. By arranging the cooling liquid feeding conduit with a
larger cross sectional area than the cooling liquid ejector outlet
nozzle it is ensured that the pressure drop in the cutting tool can
be reduced.
[0018] Optionally the cooling liquid ejector outlet nozzle has a
length between 1 mm and 3 mm. By making the cooling liquid ejector
outlet nozzle short an output spray from the nozzle will be
focussed. Long narrow channels will tend to result in a distributed
spray. By making the length of the narrow cooling liquid ejector
outlet nozzle short, the spray will thus be focused.
[0019] Optionally the cooling liquid feeding conduit is eccentric
in relation to a centre axis of said stem. Steep changes in flow
direction result in cavitation losses. The eccentric location
allows for less steep change in flow direction in the vicinity of
the cooling liquid ejector outlet nozzle.
[0020] The cutting tool preferably comprises a head located on the
top of the stem. Optionally, said head includes a first surface,
which extends in a plane in parallel with a longitudinal axis of
the cutting tool, wherein a cutting insert is located on the first
surface, and a second surface which extends in a plane which is
inclined with regard to a plane at right angles to the longitudinal
axis and which intersects with a length axis of the cooling liquid
ejector outlet nozzle. This arrangement allows that the cooling
liquid ejector outlet nozzle, which may have an exit opening in the
inclined surface which extends perpendicularly to the direction of
the inclined surface, may focus a cooling liquid jet on an edge of
a cutting insert. The location of the rim an exit opening in a
plane vertical to the length axis of the cooling liquid ejector
outlet nozzle reduces spray diffusion in comparison to when the
plane is inclined in relation to the length axis of the cooling
liquid ejector outlet nozzle.
[0021] Optionally the cutting tool includes a cutting insert which
before use has a polygonal cross sectional shape, that sides of the
polygon meet at rounded corners and that a straight portion is
present in the rounded area. Preferably, the polygon has the shape
of an equilateral triangle or a square. Optionally the cutting
insert is secured to said head such that said straight portion is
coaxial with a centre axis of a stem of said cutting tool. By
allowing the straight portion to be coaxial with the centre axis a
reduction of wear of the cutting insert and of unintended
deformation of the worked goods can be obtained. It is believed
that in the event no straight portion is present in the rounded
area a local concentration of force is obtained at the contact
between the goods and the cutting insert such that the contact
force will initially be too high with excessive wear and risk for
damage of the cutting insert as well as of the worked goods as a
consequence.
[0022] The invention also relates to a cutting insert which before
use has the shape of an equilateral triangle or a square, which
sides meet at rounded corners and that a straight portion is
present in the rounded area. Optionally, the rounded corners have a
curvature radius between 0.6 and 1.2 mm and that the straight area
has a length between 0.07 and 0.15 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Embodiments of the invention will now be described in more
detail with reference to appended drawings, where
[0024] FIG. 1 shows a perspective view of a holder for a cutting
tool,
[0025] FIG. 2 shows a cross section through a plunger along a plane
formed by the length axes of a first and second channel
respectively, when the plunger is installed in correct position in
the second channel,
[0026] FIG. 3 shows a perspective view of a plunger,
[0027] FIG. 4 shows a cross section along a plane formed by the
length axes of a first and second channel respectively, with a
plunger in a first retracted position,
[0028] FIG. 5 shows a cross section along a plane formed by the
length axes of a first and channel respectively, with a plunger in
a second projecting position,
[0029] FIG. 6 shows a top view of a holder, with a plunger in a
first retracted position,
[0030] FIG. 7 shows a top view of a holder, with a plunger in a
second projecting position,
[0031] FIG. 8 shows a cross section through a plunger as shown in
FIG. 2 further including means for locking the plunger against
movement in the length direction of the second channel,
[0032] FIG. 9 shows a side view of a cutting tool, facing a flat
surface in the head of the cutting tool,
[0033] FIG. 10 shows a side view of the cutting tool shown in FIG.
7 taken along a flat surface in the head of the cutting tool,
[0034] FIG. 11 shows a cross section of the cutting tool in FIGS. 9
and 10, and
[0035] FIGS. 12 and 13 show a cutting insert in detail.
DETAILED DESCRIPTION
[0036] In FIG. 1 a holder 1 for a cutting tool (not shown) is
shown. The holder 1 comprises a body 2. The body 2 includes a head
portion 3 and a stem portion 4. The head portion 3 includes a first
channel 6 arranged for receiving a stem of a cutting tool. The
first channel 6 extends along a first length axis 7 in a first
axial direction which is coaxial with a rotational axis when the
tool holder is mounted in a metal working machine. The head portion
3 furthermore includes a second channel 8, which intersects with
said first channel 6. The second channel 8 extends along a second
length axis 9. The first and second length axes 7, 9 are preferably
perpendicular or essentially perpendicular to each other. The first
channel 6 has in the embodiment shown in FIG. 1 a cross-section in
a plane transverse to the first length axis 7 which is of a larger
dimension than a stem of a cutting tool. More specifically, said
cross section is elongated and preferably composed of two half
circles 10a, 10b connected with two linear segments 12a, 12b. The
stem of the cutting tool having a circular cross-section may thus
be moved in direction of the second length axis.
[0037] A plunger 13 is inserted in the second channel 8. The
plunger 13 is provided with a third channel 14, see FIG. 2, the
cross section of which at least partly overlaps with the cross
section of the first channel 6 when the plunger 13 is inserted into
the body 4. In FIG. 1, part of an upper opening of the third
channel 14 is shown below an upper opening of the first channel
6.
[0038] The stem of the cutting tool inserted in the first channel 6
may thus be received in the third channel 14.
[0039] In FIG. 2 is shown a cross section through the plunger 13
along a plane formed by the length axes 7, 9 of the first and
second channel respectively, when the plunger is installed in
correct position in the second channel. The plunger 13 has a
cylindrical shape with two parallel, flat end surfaces or end walls
16a, 16b connected by an envelope surface 17. The plunger 13 may
have alternative shapes as long as it fits and in the second
channel 8 and may be secured in the second channel 8 so as to allow
a limited axial movement in the second axial direction 9. In the
drawing it is shown that the third channel 14 extends through the
plunger 13 from an upper opening 18 to a lower opening 19.
[0040] A membrane 20 forms a part of the third channel. The
membrane 20 may be formed by a cylindrical sleeve which is
introduced into an internal cavity in the wall forming the third
channel. The sleeve is sealed at its upper and lower ends. The
sleeve 20 covers an annular shaped trace 21 in the cavity forming
the third channel. The trace 21 forms a pressure chamber 22, which
has an annular shape. An interior cylindrical wall 23 of the
pressure chamber extending along the first length axis 7 is thus
defined by an envelope surface of said membrane 20, which faces
radially outwards. Part of the third channel 14 is defined by an
envelope surface of said membrane 20, which faces radially inwards.
Thus, said envelope surfaces are defined by opposite sides of a
wall 24 of said membrane. A hydraulic oil pipe 25 is connected to
the pressure chamber 22 for enabling a movement of the membrane 20
thereby enabling locking or release of the stem of the cutting
tool. The hydraulic oil pipe 25 connects the pressure chamber 22
with the end surface, or wall 16a of the plunger 13. A mechanism 26
for pressurizing the pressure chamber is located at the end wall.
In this embodiment, the mechanism for pressurising the pressure
chamber is constituted by a screw 27 arranged in a threaded bore
28. By rotating the screw such that it is moved inwardly, an
incompressible hydraulic fluid contained in the pressure chamber
and the hydraulic oil pipe would force the membrane to bulge
inwardly and grip a stem of a cutting tool, if present in the third
channel. By rotating the screw such that it is moved outwardly, the
membrane would progressively be released to assume an unloaded
position and a grip a stem of a cutting tool, if present in the
third channel, may be released. In order to facilitate filling of
the pressure chamber with suitable hydraulic oil or grease a vacuum
nipple 15 is connected to the pressure chamber via a conduit.
Filling of the chamber can then be achieved by connecting the
nipple 15 to a vacuum source while removing the screw 27 from the
bore 28 and supplying oil or grease to the conduit connected to the
bore 28.
[0041] FIG. 3 shows the plunger 13 of FIG. 2 in perspective view
positioned in the body 2. The third channel 14 is visible in the
envelope surface 17. One of the end walls 16a is provided with the
locking means 26 and the nipple 15.
[0042] In FIGS. 4 and 5 cross sections along a plane formed by the
length axes of the first and second channel 6,8 respectively, with
the plunger 13 in a first advanced position (FIG. 4) and in a
second retracted position (FIG. 5) in the body 2, are shown.
[0043] In FIGS. 6 and 7 top views of the holder, with the plunger
in the first advanced position (FIG. 6) and in the second retracted
position (FIG. 7), are shown.
[0044] The holder shown in FIGS. 4-7 comprises a mechanism 29 for
movement of the plunger along the length axis 9 of said second
channel so as to position the stem of a cutting tool in a lateral
position relatively to the body, that is along the length axis 9 of
said second channel. The mechanism 29 includes a threaded screw 30
which engages in a threaded bore 31 formed in the plunger 13 or a
nut secured to the plunger 13.
[0045] In an embodiment of the invention, as shown in FIG. 8,
locking of the plunger against movement along the length axis 9 of
said second channel may be achieved by a membrane 32 arranged in
the envelope surface 17 of the plunger. A pressure chamber 33 is
arranged inside of the membrane. The membrane is cylindrical in
shape and the pressure chamber has an annular shape. A hydraulic
oil pipe 34 is connected with the pressure chamber 33 and a
mechanism 35 is configured for pressurizing the pressure chamber 33
so as to press the membrane 32 against inner walls of the second
channel and lock the plunger against movement relative to the body.
The mechanism 35 includes a threaded screw 36 which engages in a
threaded bore 37.
[0046] As is seen in FIGS. 2-8, an indentation 38 is provided in
the plunger 13 at an upper opening 18 of the third channel 14. The
indentation 38 is arranged to receive a notch provided on said stem
of a cutting tool, thereby enabling axial and angular positioning
of the cutting tool.
[0047] In FIGS. 9 and 10 a cutting tool 40 is shown. The cutting
tool 40 includes a stem 41 arranged to be inserted into the first
and third channels of the holder for the cutting tool. The cutting
tool furthermore includes a head 42 on which a cutting insert 43 is
positioned. A notch 44 is provided on the stem 41 of the cutting
tool, thereby enabling axial and angular positioning of the cutting
tool in the holder, when the notch is positioned in a corresponding
recess in the cutting tool holder. The stem 41 preferably includes
or consists of cemented carbide and the head 42 is preferably made
of tool steel. This combination ensures that the cutting tool has a
high rigidity, while allowing formation of a carrier pocket or a
carrier wall for a cutting insert with high accuracy.
[0048] In FIG. 11 a cross section of the cutting tool in FIGS. 9
and 10 is shown. The cutting tool includes a cooling liquid flow
entrance 45 in a lower region 46 of the stem. A cooling liquid
feeding conduit 47 extends from said liquid flow entrance 45 to the
head 42 located on the top of the stem 41. A cooling liquid ejector
outlet nozzle 48 is connected to the cooling liquid feeding conduit
47 at the head 42. The cooling liquid feeding conduit 47 is
eccentric in relation to a centre axis 49 of said stem. The cooling
liquid ejector outlet nozzle 48 has a smaller cross sectional area
than said cooling liquid feeding conduit 47. The cooling liquid
ejector outlet nozzle may have a length between 1 mm and 3 mm.
[0049] The head 42 includes a first, substantially flat surface in
the form of a vertical wall 50 on which the cutting insert 43 is
located. The first flat surface 50 extends in a plane in parallel
with the length direction of the cutting tool 40. The head
furthermore includes a second, substantially flat surface 51, which
is arranged at right angles to the first flat surface. The second
flat surface 51 is further inclined with regard to a direction at
right angles to the length direction of the cutting tool 40. The
second surface forms an inclined wall 51 which extends in a plane P
intersecting with a length axis 56 of the cooling liquid ejector
outlet nozzle. The cooling liquid ejector outlet nozzle has an exit
opening 55 in the inclined wall which extend perpendicularly to the
direction of the inclined wall. A cooling liquid ejector outlet
nozzle (48) opening for the cooling liquid is located in said
second, inclined surface 51.
[0050] In FIG. 12 a cutting insert 43 before use is shown. The
cutting insert has the shape of an equilateral triangle or a
square, which sides 52 meet at rounded corners 53. A straight
portion 54 is present at the rounded corners 53. FIG. 13 shows a
corner 53 of the cutting insert in FIG. 12 in magnified view. The
rounded corners have a curvature radius between 0, 6 and 1, 2 mm
and the straight portion has a length between 0, 07 and 0, 15 mm.
Hence, the short straight portion has a curved portion located on
both it sides. In use, the cutting insert is secured to said head
such that said straight portion is coaxial with a rotational axis
of said cutting tool.
* * * * *