U.S. patent application number 11/318742 was filed with the patent office on 2007-03-15 for tool holder for the shrink-attachment of tools.
This patent application is currently assigned to Haimer GmbH. Invention is credited to Franz Haimer, Wolfgang Kuegle.
Application Number | 20070059117 11/318742 |
Document ID | / |
Family ID | 35404951 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070059117 |
Kind Code |
A1 |
Haimer; Franz ; et
al. |
March 15, 2007 |
Tool holder for the shrink-attachment of tools
Abstract
A tool holder comprising a coupling shaft, a shrink chuck and a
central member. The shrink chuck has a head and a base, the head
having a tensioning portion with a carrier comprising an axial
internal bore. The central member is interposed between the
coupling shaft and the base. A surface contour connecting the front
and rear diameters of the shrink chuck has at least two portions
substantially even relative to a diameter course of the contour at
the at least two portions. A first portion is disposed on the head
and a second portion is disposed on the base, and a transition is
interposed between the head and the base. A chuck diameter of the
shrink chuck increases in a substantially discontinuous manner at
the transition from the first portion to the second portion so that
the head is slimmer than the base.
Inventors: |
Haimer; Franz; (Igenhausen,
DE) ; Kuegle; Wolfgang; (Aichach-Griesbeckerzell,
DE) |
Correspondence
Address: |
PRICE HENEVELD COOPER DEWITT & LITTON, LLP
695 KENMOOR, S.E.
P O BOX 2567
GRAND RAPIDS
MI
49501
US
|
Assignee: |
Haimer GmbH
|
Family ID: |
35404951 |
Appl. No.: |
11/318742 |
Filed: |
December 27, 2005 |
Current U.S.
Class: |
409/234 |
Current CPC
Class: |
B23Q 11/1023 20130101;
B23B 2240/32 20130101; B23B 31/006 20130101; B23B 31/028 20130101;
Y10T 409/304032 20150115; Y10T 279/3487 20150115; Y10T 408/44
20150115; B23B 2231/24 20130101; B23B 2265/08 20130101; B23Q 11/10
20130101; B23B 31/02 20130101; B23B 2260/0725 20130101; Y10T 408/99
20150115; B23B 31/1179 20130101; B23P 11/027 20130101; Y10T
409/30952 20150115; B23C 5/28 20130101; Y10T 279/17957 20150115;
Y10T 409/308624 20150115; B23C 5/00 20130101 |
Class at
Publication: |
409/234 |
International
Class: |
B23C 3/00 20060101
B23C003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 9, 2005 |
DE |
20 2005 014 350.2 |
Claims
1. A tool holder for shrink-attachment of tools having preferably
cylindrical tool shafts, comprising: a coupling shaft for coupling
to a machine tool; a shrink chuck having a shrink chuck head and a
shrink chuck base, the shrink chuck head having a tensioning
portion with a carrier comprising an axial internal bore for
gripping the tool shaft; and a central member interposed between
the coupling shaft and the shrink chuck base; the shrink chuck
having a front diameter at the shrink chuck head for facing towards
the machine tool and a rear diameter at the shrink chuck base
facing towards the central member; wherein a surface contour
connecting the front and rear diameters of the shrink chuck has at
least two portions substantially even relative to a diameter course
of the contour at the at least two portions, the at least two
portions comprising a first portion and a second portion, the first
portion being disposed on the shrink chuck head and the second
portion being disposed on the shrink chuck base, and a transition
being interposed between the shrink chuck head and the shrink chuck
base, a chuck diameter of the shrink chuck increasing in a
substantially discontinuous manner at the transition from the first
portion to the second portion so that the shrink chuck head is
slimmer than the shrink chuck base.
2. A tool holder in accordance with claim 1, wherein: the carrier
has an axial limit stop for determining an axial position of the
tool shaft within the carrier; and the axial limit stop, when
viewed axially, is located at a height or between the position of
the transition and a front end of said shrink chuck head so that,
in a gripped state relative to the central member, a lower end of
the tool shaft, when viewed axially, is located before or at the
height of the transition.
3. A tool holder in accordance with claim 2, wherein: the first
portion runs between the front end of the shrink chuck head and the
transition, and has a substantially conical periphery.
4. A tool holder in accordance with claim 3, wherein: a diameter of
the periphery extending towards the transition at an angle relative
to a longitudinal axis of the tool holder at about 1.degree. to
20.degree..
5. A tool holder in accordance with claim 4, wherein: the angle is
about 4.5.degree..
6. A tool holder in accordance with claim 3, wherein: the diameter
of the surface contour of the shrink chuck extends at the
transition from the first portion to the second portion towards the
shrink chuck base at an angle perpendicular to the tool holder's
longitudinal axis at about 0.degree. to 50.degree..
7. A tool holder in accordance with claim 6, wherein: the angle is
about 10.degree. to 40.degree..
8. A tool holder in accordance with claim 7, wherein: the angle is
about 30.degree..
9. A tool holder in accordance with claim 1, wherein: a third
portion is interposed between the central member and the second
portion, the third portion having a substantially cylindrical
periphery and the diameter of a periphery of the second portion
flaring out towards the central member at an angle relative to the
tool holder's longitudinal axis at about 1.degree. to 20.degree., a
transition of the surface contour occurring substantially
continuously between the second and third portions.
10. A tool holder in accordance with claim 9, wherein: the angle is
about 6.degree. if the tool holder has a hollow shaft coupling.
11. A tool holder in accordance with claim 9, wherein: the angle is
about 8.degree. if the tool holder has a tapered shaft
coupling.
12. A tool holder in accordance with claim 1, wherein: a third
portion is interposed between the central member and the second
portion and a fourth portion is interposed between the third
portion and the central member, the second portion and the fourth
portion having substantially cylindrical peripheries and the third
portion having a substantially conical periphery, a diameter of the
periphery of the third portion extending towards the central member
at an angle relative to the tool holder's longitudinal axis at
about 1.degree. to 20.degree., transitions of the surface contour
occurring substantially continuously between the second and third
portions and between the third and forth portions.
13. A tool holder in accordance with claim 12, wherein: the angle
is about 6.degree. if the tool holder has a hollow shaft
coupling.
14. A tool holder in accordance with claim 12, wherein: the angle
is about 8.degree. if the tool holder has a tapered shaft
coupling.
15. A tool holder in accordance with claim 1, wherein: bores for
counter-balancing members are provided within the second
portion.
16. A tool holder in accordance with claim 1, wherein: the tool
holder includes an axial internal bore as a cooling fluid supply
channel, the supply channel having a diameter of about 3 mm to 6
mm.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to German Patent
Application No. 20 2005 014 350.2 filed on Sep. 9, 2005.
Field of the Invention
[0002] The present invention relates to a tool holder for the
shrink-attachment of tools having preferably cylindrical shafts or
shanks.
BACKGROUND OF THE INVENTION
[0003] Tool holders for holding cylindrical shafts or shanks have
been known for a long time.
[0004] They are used to hold lathe, drilling, fretting/reaming,
grinding and milling/cutting tools and comprise a shrink lining or
chuck that has a tensioning portion with an axial internal bore
within which the tool shaft can be attached by means of
shrinking.
[0005] During the shrinkage process, the tensioning portion, the
internal bore of which has a slightly smaller internal diameter
than the external diameter of the tool shaft, is expanded via the
application of heat, preferably by means of an induction coil, and
is cooled down again after the tool shaft has been inserted,
thereby forming a torque-resistant connection between the tool
shaft and the shrink chuck.
[0006] Hitherto known designs for such tool holders, as are shown,
for example, in DE 199 44 440 C2 and DE 101 14 149 C2, already
exhibit very good vibration damping and rotational stability. These
tool holders do, however, still run the risk of becoming prone to
vibrations especially when used with very high-speed rotating
tools, whereby the tool, while being rotated, may perform a more or
less precision movement around the longitudinal axis of the tool
holder and hence the precision and reproducibility of any
workpieces made therewith may be diminished. To ensure nevertheless
a high degree of accuracy and reproducibility, such tools must, in
consequence, not be used at extreme rotational speeds, and the feed
rate and cutting depth must not be selected to be too high either.
This approach is not ideal, however, in terms of the quantity of
material removed, thus preventing the machine operating time for
each manufactured workpiece from being optimized.
[0007] However, this kind of tool holder does not just entail
drawbacks in the case of rapid-rotation tools. In the case of
non-rotating tools, as well, the influence of the workpiece that is
to be machined may cause the tool to be deflected out of the
tool-holder axis and bring about vibrations that likewise place
limits on machining precision.
[0008] It is therefore the present invention's object to provide a
shrink-attachment type tool holder that is less prone to vibrations
and thus enables more material to be removed via machining.
SUMMARY OF THE INVENTION
[0009] A tool holder in accordance with the present invention is
characterized by a shrink chuck contour course in which the shrink
chuck diameter extends, in a discontinuous manner, between a first,
front diameter at the shrink chuck head and a second, rear diameter
at the shrink chuck base in such a way as to form at least two
shrinking lining contour portions. In addition, the transition
between the first portion and the second portion, in which the
diameter rises discontinuously, defines the transition between the
shrink chuck head and base.
[0010] Not only does this special shape make the shrink chuck head
slimmer than the base, but it also lets the head have much less
mass, which might give rise to and intensify vibrations, for
example, whenever the tool holder is rotated very fast. Such a tool
holder may therefore be operated at much higher rotational speeds
than conventional tool holders, with the reduced susceptibility to
vibrations making it possible to manufacture workpieces with
excellent precision and reproducibility. As a result of the fact
that the shrink chuck base is designed to have thicker walls than
the head, not only are standardized specifications relating to the
tool holder design and resulting from the geometrical structure of
the machine/tool holder interface complied with, but, at the same
time, the shrink chuck is ensured sufficiently high rigidity as
well.
[0011] In an advantageous embodiment, the tool shaft carrier has an
axial limit stop that serves to determine the tool shaft's axial
position within the carrier, i.e., a limit stop which determines
the tool shaft's penetration depth into the shrink chuck. In
relation to the transition, the axial limit stop is arranged such
as to receive the tool shaft completely within the shrink chuck
head and such that the tool shaft does not partially project into
the shrink chuck base. In other words, the axial limit stop is
intended to be placed at the height of the transition or between
this and the front end of the shrink chuck head, and it is not
supposed to be placed within the region between the transition and
the lower end of the shrink chuck base. On the one hand, this
special axial configuration of the axial limit stop relative to the
transition creates a particularly beneficial ratio between the
reduced-mass shrink chuck head and the more rigid shrink chuck
base. On the other hand, the shrink chuck head can be heated easily
by means, for example, of an induction coil, the geometry of which
does not need to be complicated. Furthermore, this approach enables
the shrink chuck head to be heated and expanded as evenly as
possible because there are similar wall thicknesses throughout the
tensioning portion, thus stopping the tensioning portion from
unevenly heating up and expanding.
[0012] The first portion preferably has a conical contour that runs
uniformly between the front end of the shrink chuck head and the
transition, and the diameter of this first portion extends towards
the transition within an angular range of 1.degree. to 20.degree.,
especially 4.5.degree., relative to the tool holder's longitudinal
axis. If the shrink chuck head is lent such a geometrical design,
the tool holder is compatible with all conventional shrinkage
devices.
[0013] At the transition, the extension of the shrink chuck contour
diameter can run in a range from abruptly, i.e., 0.degree. in terms
of being perpendicular to the tool holder's longitudinal axis, up
to 50.degree.. Preference is given to a range from 10.degree. to
40.degree., with particular preference being given to the
transition's extension at 30.degree..
[0014] At the lower end of the shrink chuck base adjacent to the
central member of the tool holder, the second portion is preferably
adjoined by a third portion which has an essentially cylindrical
contour, with the second portion having an essentially conical
contour that extends towards the third portion at an angle relative
to the longitudinal axis in the range of 1.degree. to 20.degree.,
particularly 6.degree. in the case of a tool holder with a hollow
shaft coupling, and 8.degree. in the case of a tool holder with a
tapered shaft coupling. The contour-related transition between the
second and third portions occurs in an essentially constant manner,
though discontinuous transitions are possible, too. In this way,
the base has a standardized contour adjacent to the central member
of the tool holder, whereas the region between the third portion
and the transition is, on account of the conical contour, reduced
additionally in terms of its wall thickness, thereby further
reducing the shrink chuck in terms of its mass. As a result, the
tool holder's susceptibility to vibrations is further reduced as
well.
[0015] Particularly in the case of tool holders that have long
shrink chucks, it is advantageous for the shrink chuck region to
exhibit a four-section contour course, namely a first portion, a
second, essentially cylindrical portion adjoining the transition,
followed by a flared third portion, which is in turn adjoined by a
fourth, essentially cylindrical portion that adjoins the central
member and complies with standardized specifications. The conical
contour of the third portion is intended to extend towards the
central member at an angle relative to the longitudinal axis of the
tool holder in the range of 1.degree. to 20.degree., especially
6.degree. in the case of a tool holder with a hollow shaft
coupling, and 8.degree. in the case of a tool holder with a tapered
shaft coupling, with the contour-related transitions between the
second and third or the third add fourth portions running in an
essentially constant manner, though discontinuous transitions are
possible, too. Compared to a three-section contour design, the
above four-section contour design permits the shrink chuck base
mass to be additionally reduced.
[0016] In a preferred embodiment, the second portion has bores into
which counter-balancing members, particularly counter-balancing
screws, can be inserted, which members are used to make
concentricity possible by preventing the tool holder from
exhibiting imbalances.
[0017] An axial internal bore within the tool holder is
advantageously provided for cooling the tool while the workpiece is
being machined; this bore supplies a cooling fluid to the tool or
to the point where the tool engages with the workpiece. This supply
channel preferably has a diameter ranging from 3 mm to 6 mm,
thereby still ensuring that the tool holder exhibits sufficiently
high rigidity. The cooling fluid supplied through the axial supply
channel can be supplied to the point where the tool engages with
the workpiece either directly via an axial internal bore through
the tool to simultaneously cool the tool from within and/or a
plurality of bores is provided in the wall of the shrink chuck
head, which bores receive the cooling fluid from the supply channel
and guide the fluid next to the tool shaft within the tool holder
wall, thus causing the cooling fluid to exit the shrink chuck head
next to the tool. Alternatively, the coolant lines can be omitted,
too, so as to increase rigidity.
[0018] Further characteristics, features and advantages of the
present invention will now be explained by describing a preferred
exemplary embodiment in conjunction with the figures, wherein
[0019] These and other features, advantages and objects of the
present invention will be further understood and appreciated by
those skilled in the art by reference to the following
specification, claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows a longitudinal sectional view of a preferred
embodiment of a tool holder, and
[0021] FIG. 2 contains information to explain the tool holder's
dimensions in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] For purposes of description herein, the terms "upper,"
"lower," "right," "left," "rear," "front," "vertical,"
"horizontal," and derivatives thereof shall relate to the invention
as orientated in FIG. 1. However, it is to be understood that the
invention may assume various alternative orientations, except where
expressly specified to the contrary. It is also to be understood
that the specific devices and processes illustrated in the attached
drawings, and described in the following specification are simply
exemplary embodiments of the inventive concepts defined in the
appended claims. Hence, specific dimensions and other physical
characteristics relating to the embodiments disclosed herein are
not to be considered as limiting, unless the claims expressly state
otherwise.
[0023] FIG. 1 represents as a longitudinal section a tool holder 1
that comprises a hollow shaft coupling 2, a central member 3 and a
shrink chuck 4. The shrink chuck 4 has a shrink chuck base 5, the
lower region of which is adjacent to the central member 3, and the
shrink chuck 4 also has a shrink chuck head 6. It is very easy to
identify the four-part contour course of the shrink chuck 4, which
course has a first, conical portion 7, a second cylindrical portion
8, a third, conical portion 9 and a fourth, cylindrical portion 10.
These portions 7, 8, 9 and 10 connect the essentially rotationally
symmetrical contour course of the shrink chuck 4 starting out from
a front diameter D1 of the shrink chuck head 6 and terminating at
the rear diameter D4 of the shrink chuck base 5.
[0024] The contour course of the tool holder diameter runs in an
essentially even manner within the individual portions 7, 8, 9 and
10 and constantly between the portions 8, 9 and 10, with the
diameter of the shrink chuck 4 increasing continuously starting out
from the front diameter D1 as far as the rear diameter D4 and
remaining essentially constant only within the second and fourth
portions 8 and 10. The diameter increases discontinuously within
the transition region 11, i.e., the contour diameter exhibits a
discontinuous course during the transition from the first portion 7
to the second portion 8.
[0025] As a result of the transition 11, the shrink chuck base 5
has a much larger wall thickness than the shrink chuck head 6,
which makes the shrink chuck head 6 not only look slimmer, but also
reduces its mass compared to a shrink chuck head 6 whose contour
course runs continuously starting out from the shrink chuck base
5.
[0026] These measures lower considerably the susceptibility of the
tool holder 1 to vibrations, because less mass is located far away
from the attachment point of the tool holder 1 within the machine
tool and greater mass is placed close to this attachment point. At
the same time, the tool holder 1 shown in FIG. 1 exhibits
sufficiently high rigidity and complies in particular with
standardized specifications that, for example, define the maximum
diameter of the fourth portion 10.
[0027] In its front region, the shrink chuck head 6 has a
tensioning portion that is characterized by an axial internal bore
12 for receiving the tool shaft. The tool shaft's axial penetration
depth into the axial internal bore 12 is determined by an axial
limit stop 13 that is designed in the shape of a radial
constriction of the internal bore 12. As a result of the axial
limit stop 13, the tool shaft is in a gripped state only within the
shrink chuck head 6, but not in the shrink chuck base 5, thus
simplifying and facilitating the shrinkage process
considerably.
[0028] Adjoining the axial limit stop 13 is a supply channel 14
that is likewise designed as an axial internal bore and supplies
coolant to the tool shaft that has been shrunk within the bore 12.
The coolant can be fed to the tool head and workpiece either via a
coolant channel guided axially within the tool and/or bores (not
shown) can be provided within the shrink chuck head 6, which bores,
starting out from the supply channel 14, guide the coolant within
the wall of the shrink chuck head 6 past the tool shaft to the
front end of the shrink chuck head 6. This may, for instance, be
brought about by means of two bores that are arranged
mirror-symmetrically relative to the longitudinal axis of the tool
holder 1 and which run within the first portion 7 next to the tool
shaft inside the wall.
[0029] In addition, one or more grooves (not shown) can be provided
within the bore 12; designed as depressions, these grooves
partially increase the internal diameter of the bore 12.
[0030] Once the tool shaft has been shrunk into the bore 12, the
bore 12 would consequently not be in direct physical contact with
the tool shaft in the region of these grooves, thereby forming
cavities in these regions; such cavities beneficially receive any
moisture, lubricant etc. adhering to the tool shaft so that
hydraulic bearings (or hydromounts), which would impede the
complete transmission of torque, could not be formed between the
bore 12 and the tool shaft. In this respect, a plurality of grooves
that run, for example, parallel to the axis or radially relative
thereto is preferably replaced by a spirally shaped groove.
[0031] FIG. 2 depicts the tool holder 1 from FIG. 1 again as a
longitudinal section, though individual dimensions are defined more
precisely. The following tables indicate examples of values for the
individual dimensions. These values are all given in mm or in
.degree. for the dimensions , and and are listed as a function of
the type of tool holder coupling shaft 2 and the shrink chuck's
total length L4.
[0032] All dimensional data relate to a lower diameter D4 of the
shrink chuck base 5 of 50 mm or 53 mm, which diameter is specified
in standards by the choice of machine interface. Accordingly,
Tables 1, 2, 3 and 4 only go up to a tool shaft diameter D1 of 16
mm, because, if the tool shaft diameters D1 were larger, such a
discontinuous transition 11 would essentially no longer be
realizable using standard materials.
[0033] To provide rotationally stable tool holders in accordance
with the present invention in regard to larger tool shaft diameters
D1 as well, i.e., tool holders that have the above-described
contour course, for applications in high rotational-speed ranges,
it would be necessary to make use of larger interfaces that would
permit larger diameters D4 of the fourth portion 10.
[0034] The angle data for the dimensions , and depend on the choice
of the shrink chuck's total length L4 and on the diameter D4 of the
shrink chuck base 5. In consequence, they are constant in each of
Tables 1, 2, 3 and 4. TABLE-US-00001 TABLE 1 D1 D2 D3 D4 L1 L2 L3
L4 L5 L6 L7 .alpha. .beta. .gamma. 6 21 40 53 48.5 60.5 84 104 130
38 162 30 4.5 6 8 21 40 53 48.5 60.5 84 104 130 38 162 30 4.5 6 10
24 40 53 55 65.5 84 104 130 43 162 30 4.5 6 12 24 40 53 55 65.5 84
104 130 48 162 30 4.5 6 14 27 42 53 60.5 70.5 84 104 130 48 162 30
4.5 6 16 27 42 53 60.5 70.5 84 104 130 51 162 30 4.5 6
[0035] Table 1 lists dimensional data for a tool holder 1 having a
hollow shaft coupling 2 for a first shrink chuck length L4.
TABLE-US-00002 TABLE 2 D1 D2 D3 D4 L1 L2 L3 L4 L5 L6 L7 .alpha.
.beta. .gamma. 6 21 40 53 48.5 60.5 114 134 160 38 192 30 4.5 6 8
21 40 53 48.5 60.5 114 134 160 38 192 30 4.5 6 10 24 40 53 55 65.5
114 134 160 43 192 30 4.5 6 12 24 40 53 55 65.5 114 134 160 48 192
30 4.5 6 14 27 42 53 60.5 70.5 114 134 160 48 192 30 4.5 6 16 27 42
53 60.5 70.5 114 134 160 51 192 30 4.5 6
[0036] Table 2 lists dimensional data for a tool holder 1 having a
hollow shaft coupling 2 for a second shrink chuck length L4.
TABLE-US-00003 TABLE 3 D1 D2 D3 D4 L1 L2 L3 L4 L5 L6 L7 .alpha.
.beta. .gamma. 6 21 40 50 48.5 60.5 91 110.9 130 38 198.4 30 4.5 8
8 21 40 50 48.5 60.5 91 110.9 130 38 198.4 30 4.5 8 10 24 40 50 55
65.5 91 110.9 130 43 198.4 30 4.5 8 12 24 40 50 55 65.5 91 110.9
130 48 198.4 30 4.5 8 14 27 42 50 60.5 70.5 91 110.9 130 48 198.4
30 4.5 8 16 27 42 50 60.5 70.5 91 110.9 130 51 198.4 30 4.5 8
[0037] Table 3 lists dimensional data for a tool holder 1 having a
tapered shaft coupling (not shown) for a first shrink chuck length
L4, whereby the shape of the tool holder 1 that has a tapered shaft
coupling differs from the shape of a tool holder 1 that has a
hollow shaft coupling 2 only in the region of the coupling shaft
and central member. TABLE-US-00004 TABLE 4 D1 D2 D3 D4 L1 L2 L3 L4
L5 L6 L7 .alpha. .beta. .gamma. 6 21 40 50 48.5 60.5 121 140.9 160
38 228.4 30 4.5 8 8 21 40 50 48.5 60.5 121 140.9 160 38 228.4 30
4.5 8 10 24 40 50 55 65.5 121 140.9 160 43 228.4 30 4.5 8 12 24 40
50 55 65.5 121 140.9 160 48 228.4 30 4.5 8 14 27 42 50 60.5 70.5
121 140.9 160 48 228.4 30 4.5 8 16 27 42 50 60.5 70.5 121 140.9 160
51 228.4 30 4.5 8
[0038] Table 4 lists dimensional data for a tool holder 1 having a
tapered shaft coupling (not shown) for a second shrink chuck length
L4.
[0039] The above-mentioned data make it apparent that a tool holder
1 in accordance with the present invention is much less prone to
vibrations than known tool holders, thereby permitting, inter alia,
higher rotational speeds so that the quantity of material that is
removed during machining and determined by the tool speed, the tool
feed rate and the tool's cutting depth can be increased, thus
simultaneously decreasing the machine operating times needed to
manufacture a workpiece. Accordingly, a tool holder according to
the present invention enables workpieces to be made and machined
much more efficiently and with greater economy.
[0040] The above description is considered that of the preferred
embodiment only. Modification of the invention will occur to those
skilled in the art and to those who make or use the invention.
Therefore, it is understood that the embodiment shown in the
drawings and described above is merely for illustrative purposes
and not intended to limit the scope of the invention, which is
defined by the following claims as interpreted according to the
principles of patent law, including the doctrine of
equivalents.
* * * * *