U.S. patent application number 13/450691 was filed with the patent office on 2013-10-24 for cutting tool and cutting tool holder having lever pin.
This patent application is currently assigned to Iscar, Ltd.. The applicant listed for this patent is Gil Hecht. Invention is credited to Gil Hecht.
Application Number | 20130279997 13/450691 |
Document ID | / |
Family ID | 48325823 |
Filed Date | 2013-10-24 |
United States Patent
Application |
20130279997 |
Kind Code |
A1 |
Hecht; Gil |
October 24, 2013 |
CUTTING TOOL AND CUTTING TOOL HOLDER HAVING LEVER PIN
Abstract
A tool holder includes an insert pocket having a support surface
with a pocket recess occupied by a lever pin, and a fastening
member. A head portion of the lever pin has a lever head rear
contact surface, located above the support surface, for pressing
against a bore of a cutting insert in the insert pocket. The
fastening member engages a threaded recess which extends from the
pocket recess along a threaded recess axis. The fastening member
includes a guiding prong, located within a blind hole in the front
of the lever pin. A clamping contact surface of the fastening
member is adjacent to a lever front contact surface of the lever
pin. A first longitudinal distance, between the lever rear contact
surface and the lever front contact surface, is smaller than a
second longitudinal distance, between the lever front contact
surface and a lever rear contact surface.
Inventors: |
Hecht; Gil; (Nahariya,
IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hecht; Gil |
Nahariya |
|
IL |
|
|
Assignee: |
Iscar, Ltd.
Tefen
IL
|
Family ID: |
48325823 |
Appl. No.: |
13/450691 |
Filed: |
April 19, 2012 |
Current U.S.
Class: |
407/105 |
Current CPC
Class: |
B23B 2200/165 20130101;
Y10T 407/2278 20150115; B23B 27/045 20130101; Y10T 407/2274
20150115; B23B 2205/04 20130101; B23B 27/1614 20130101; B23B 29/043
20130101 |
Class at
Publication: |
407/105 |
International
Class: |
B23B 27/16 20060101
B23B027/16 |
Claims
1. A tool holder (100) comprising: an insert pocket (102)
comprising: an insert pocket front surface (108), an insert pocket
rear portion (106), and an insert pocket support surface (110)
extending therebetween; an insert pocket top surface (114), with at
least one support wall (112) extending between the insert pocket
support surface (110) and the insert pocket top surface (114); a
pocket recess (116) opening out to, and extending downwards from
the insert pocket support surface (110); and a threaded recess
(118) opening out to the insert pocket front surface (108) and to
the pocket recess (116), the threaded recess (118) having a
threaded recess axis (T); a lever pin (120) having a top end
(125a), a bottom end (125b) and a lever pin longitudinal axis (A),
and located within the pocket recess (116), the lever pin (120)
comprising: a head portion (122), having thereon a lever head rear
contact surface (C), located above the insert pocket support
surface (110); a lever front surface (124), extending downwards
from the head portion (122), at least a portion of the lever front
surface (124) sloping in a slope angle (6) relative to the lever
pin longitudinal axis (A), the lever front surface (124) having
thereon a lever front contact surface (H), located downwards from
the lever head rear contact surface (C) by a first longitudinal
distance (h1); a blind hole (126) opening out to, and extending
from, the lever front surface (124) towards the lever pin
longitudinal axis (A), the blind hole (126) located along the
threaded recess axis (T); a base portion (121) provided with a
rocker pivot portion (128) to enable tilting of the lever pin (120)
about the rocker pivot portion (128), in the forward-rearward
directions (D.sub.F, D.sub.R); and a lever lower rear contact
surface (G), located downwards from the lever front contact surface
(H) by a second longitudinal distance (h2); and a fastening member
(130) comprising a first end (131) having thereon a clamping
contact surface (B), a second end (133), a threading surface (132)
extending between the first and second ends (131, 133), and a
guiding prong (134) extending from the first end (131), the
threading surface (132) engages the threaded recess (118), the
guiding prong (134) is located within the blind hole (126), and the
clamping contact surface (B) is adjacent to the lever front contact
surface (H); wherein in a side view of the lever pin (120), the
first longitudinal distance (h1) is smaller than the second
longitudinal distance (h2).
2. The tool holder (100) according to claim 1, wherein the pocket
recess (116) has an oval-shape cross section (136).
3. The tool holder (100) according to claim 1, wherein at least a
portion of each of the at least one support wall (112) forms a
pocket dovetail angle (.beta.) with the insert pocket support
surface (110).
4. The tool holder (100) according to claim 1, wherein the insert
pocket (102) comprises two support walls (112), converging
rearwards in a support wall convergence angle (.gamma.), in a view
taken perpendicular to the support surface (110).
5. The tool holder (100) according to claim 1, wherein locating the
guiding prong (134) within the blind hole (126) prevents the lever
pin (120) from rotating about, and from moving along, the lever pin
longitudinal axis (A).
6. The tool holder (100) according to claim 1, wherein the pocket
recess (116) extends parallel to the insert pocket front surface
(108).
7. A cutting tool (101) comprising the tool holder (100) according
to claim 1, and a cutting insert (140), located in the insert
pocket (102) of the tool holder (100), the cutting insert (140)
comprising a first surface (142), a second surface (144), a
peripheral surface (146) extending there between, and an insert
bore (148) opening out to at least the second surface (144), the
insert bore (148) having a longitudinal central bore axis (I)
perpendicular to the first and second surfaces (142, 144), the
peripheral surface (146) having at least one side abutment surface
(150) forming an insert dovetail angle (.alpha.) with the second
surface (144).
8. The cutting tool (101) according to claim 7, wherein the pocket
recess (116) has a pocket recess contact surface (J) on a rear wall
(138) thereof, and the insert bore (148) has an insert bore rear
contact surface (K), the insert dovetail angle (.alpha.) conforms
to the pocket dovetail angle (.beta.), and wherein in a fastened
position of the cutting tool (101): the second surface (144) abuts
the insert pocket support surface (110); the head portion (122) is
located within the insert bore (148), such that the lever head rear
contact surface (C) presses against the insert bore rear contact
surface (K); the clamping contact surface (B) of the fastening
member (130) presses against the lever front contact surface (H);
the lever lower rear contact surface (G) presses against the pocket
recess contact surface (J); each side abutment surface (150) is
pressed against an associated support wall (112), in a dovetail
manner; and a third longitudinal distance (h3) between the insert
bore contact surface (K) and the second surface (144) is smaller
than a fourth longitudinal distance (h4) between the insert bore
rear contact surface (K) and the first surface (142).
9. The cutting tool (101) according to claim 8, wherein the
fastening member (130) applies a first lateral rearward force
(F.sub.B,H) on the lever pin (120) at the lever front contact
surface (H).
10. The cutting tool (101) according to claim 8, wherein the lever
pin (120) applies a second lateral rearward force (F.sub.C,K) on
the cutting insert (140) at the insert bore rear contact surface
(K).
11. The cutting tool (101) according to claim 8, wherein the lever
pin (120) applies a third lateral rearward force (F.sub.G,J) on the
pocket recess (116) at the pocket recess contact surface (J).
12. The cutting tool (101) according to claim 8, wherein in the
fastened position, the lever pin longitudinal axis (A)
substantially coincides with the longitudinal central bore axis
(I).
13. The cutting tool (101) according to claim 8, wherein in a
released position, when the cutting insert (140) is located on the
insert pocket support surface (110), the lever pin longitudinal
axis (A) forms a tilt angle (.theta.), with the longitudinal
central bore axis (I).
14. The cutting tool (101) according to claim 8, wherein each
support wall (112) applies a normal force (F.sub.N) on the
associated side abutment surface (150), the normal force (F.sub.N)
being perpendicular to the associated side abutment surface (150)
and having a downward force component (F) with a magnitude of:
F.sub.N cos .alpha..
15. The cutting tool (101) according to claim 7, wherein the insert
bore (148) is a blind bore opening out only to the second surface
(144).
16. The cutting tool (101) according to claim 7, wherein the insert
bore (148) is a through bore opening out to the first surface (142)
and to the second surface (144).
17. The cutting tool (101) according to claim 7, wherein the
cutting insert (140) comprises two side abutment surfaces (150),
converging rearwards in an insert rearward convergence angle
(.phi.), in a view taken perpendicular to the first surface
(142).
18. The cutting tool (101) according to claim 17, wherein the
insert rearward convergence angle (.phi.) conforms to the support
wall rearward convergence angle (.gamma.).
Description
FIELD OF THE INVENTION
[0001] The present invention relates to metal cutting tools and
holders for cutting inserts, for metal cutting processes in
general, and to a tool holder for cutting inserts for turning
operations, in particular.
BACKGROUND OF THE INVENTION
[0002] Metal cutting tools used in turning operations, including
cutting inserts which are removably secured in a holder, have long
since provided a suitably hard material, i.e. cemented carbide, in
the vicinity of the cutting edge, where the cutting tool holder,
manufactured from a less hard material, is reusable following the
disposal of a worn or damaged cutting insert.
[0003] Cutting inserts are clamped within insert receiving pockets
located on the front of the tool holder, for holding and supporting
cutting inserts during operation (e.g., turning operation). Holders
for cutting inserts may have a clamping member contacting a hole in
the cutting insert thereby fastening the cutting insert in the
insert pocket. The holders may further have a screw member for
exerting pressure on the clamping member to contact the cutting
insert. Examples of such tool holders for cutting inserts are
disclosed in the following publications: U.S. Pat. No. 3,469,296,
U.S. Pat. No. 3,997,951, U.S. Pat. No. 4,166,711, U.S. Pat. No.
4,615,650, U.S. Pat. No. 6,158,928, U.S. Pat. No. 6,582,162 and
EP0450542A1.
[0004] It is an object of the subject matter of the present
application to provide an improved novel tool holder for cutting
insert having a lever pin and a front fastening member, and a
cutting tool employing such a tool holder, in particular for
cutting inserts with a blind bore therein. The novel tool holder
provides better clamping leverage applied on the cutting insert, as
well as a dovetail abutment against the insert pocket of the tool
holder.
SUMMARY OF THE INVENTION
[0005] In accordance with the subject matter of the present
application, there is provided a tool holder comprising:
[0006] an insert pocket comprising: [0007] an insert pocket support
surface extending from an insert pocket rear portion, in a forward
direction, towards an insert pocket front surface; [0008] at least
one support wall extending from the insert pocket support surface
to an insert pocket top surface, in an upward direction; [0009] a
pocket recess opening out to, and extending downwards from, the
insert pocket support surface; and [0010] a threaded recess opening
out to the insert pocket front surface and to the pocket recess,
the threaded recess having a threaded recess axis;
[0011] a lever pin having a top end, a bottom end and a lever pin
longitudinal axis, located within the pocket recess, the lever pin
comprising: [0012] a head portion, having thereon a lever head rear
contact surface, located above the insert pocket support surface;
[0013] a lever front surface, extending downwards from the head
portion, at least a portion of the lever front surface sloping in a
slope angle relative to the lever pin longitudinal axis, the lever
front surface having thereon a lever front contact surface, located
downwards from the lever head rear contact surface by a first
longitudinal distance; [0014] a blind hole opening out to, and
extending from, the lever front surface towards the lever pin
longitudinal axis, the blind hole located along the threaded recess
axis; and [0015] a base portion provided with a rocker pivot
portion to enable tilting of the lever pin about the rocker pivot
portion, in the forward-rearward directions; and [0016] a lever
rear contact surface, located downwards from the lever front
contact surface by a second longitudinal distance; and
[0017] a fastening member comprising a first end having thereon a
clamping contact surface, a second end, a threading surface
extending between the first and second ends, and a guiding prong
extending from the first end generally perpendicular to the first
end, the threading surface engaging the threaded recess and
locating the guiding prong within the blind hole and the clamping
contact surface adjacent to the lever front contact surface;
[0018] wherein in a side view of the lever pin, the first
longitudinal distance is smaller than the second longitudinal
distance.
[0019] In accordance with another embodiment of the subject matter
of the present application, there is provided a cutting tool
comprising the tool holder according to the above, and a cutting
insert, located in the insert pocket of the tool holder. The
cutting insert includes a first surface, a second surface, a
peripheral surface extending there between, and an insert bore
opening out to at least the second surface. The insert bore has a
longitudinal central bore axis perpendicular to the first and
second surfaces. The peripheral surface has at least one side
abutment surface forming an insert dovetail angle with the second
surface.
BRIEF DESCRIPTION OF THE FIGURES
[0020] For a better understanding of the present application and to
show how the same may be carried out in practice, reference will
now be made to the accompanying drawings, in which:
[0021] FIG. 1 is a perspective exploded view of a cutting tool in
accordance with one embodiment of the disclosed technique;
[0022] FIG. 2 is a perspective view of the cutting tool of FIG. 1,
in an assembled position;
[0023] FIG. 3 is a cross section view of the cutting tool of FIG.
2, in an assembled position, as per cutting line III-III;
[0024] FIG. 4 is a cross section view of the cutting tool of FIG.
1, in a released position;
[0025] FIG. 5 is a cross section view of the cutting tool of FIG.
2, in an assembled position, as per cutting line V-V;
[0026] FIG. 6 is a side view of the lever pin and the fastening
member of the tool holder of the cutting tool of FIG. 1;
[0027] FIG. 7 is a cross section view of the lever pin and the
fastening member shown in FIG. 6, as per cutting line VII-VII;
[0028] FIG. 8 is a perspective view of the cutting tool of FIG. 1,
with the cutting insert detached from the tool holder;
[0029] FIG. 9 is a top view of the tool holder of the cutting tool
of FIG. 8;
[0030] FIG. 10 is a perspective view of the fastening member of the
tool holder of FIG. 1; and
[0031] FIG. 11 is a top view of the cutting insert of the cutting
tool of FIG. 1.
[0032] It will be appreciated that for simplicity and clarity of
illustration, elements shown in the figures have not necessarily
been drawn to scale. For example, the dimensions of some of the
elements may be exaggerated relative to other elements for clarity,
or several physical components may be included in one functional
block or element. Further, where considered appropriate, reference
numerals may be repeated among the figures to indicate
corresponding or analogous elements.
DETAILED DESCRIPTION OF THE INVENTION
[0033] In the following description, various aspects of the subject
matter of the present application will be described. For purposes
of explanation, specific configurations and details are set forth
in sufficient detail to provide a thorough understanding of the
present invention. However, it will also be apparent to one skilled
in the art that the subject matter of the present invention can be
practiced without the specific configurations and details presented
herein.
[0034] The present invention relates to a tool holder, having a
lever pin and a front fastening member, in particular for holding
cutting inserts with a blind bore at the bottom surface thereof.
The invention also relates to a cutting tool including such a tool
holder and a cutting insert with a hole opening out to the bottom
surface thereof, for machining a work piece, for example in turning
operations.
[0035] Attention is drawn to FIGS. 1-11, depicting various views of
the cutting tool and the tool holder, according to an embodiment of
the present invention. FIG. 1 depicts an exploded perspective view
of a cutting tool 101, including a tool holder 100 and a cutting
insert 140. The tool holder 100 comprises an insert pocket 102, a
lever pin 120 and a fastening member 130. The insert pocket 102
includes an insert pocket rear portion 106 and an insert pocket
front surface 108.
[0036] An insert pocket support surface 110 extends from the insert
pocket rear end 106 towards the insert pocket front surface 108, in
a forward direction D.sub.F (indicated in FIG. 3). According to
some embodiments, the insert pocket front surface 108 is
perpendicular to the insert pocket support surface 110.
[0037] At least one support wall 112 extends from the insert pocket
support surface 110 to an insert pocket top surface 114, in an
upward direction U. As best shown in FIG. 5, at least a portion of
the support wall 112 forms a pocket dovetail angle .beta. with the
insert pocket support surface 110. According to an embodiment of
the disclosed technique, the insert pocket 102 includes two support
walls 112, converging rearwards in a support wall rearward
convergence angle .gamma., when viewed perpendicular to the support
surface 110 (FIG. 9).
[0038] A pocket recess 116 opens out to the insert pocket support
surface 110, and extends downwards from the insert pocket support
surface 110 towards a recess floor 117 of the pocket recess 116.
According to an embodiment of the present invention, the pocket
recess 116 extends perpendicular to the insert pocket support
surface 110 and parallel to the insert pocket front surface
108.
[0039] A threaded recess 118 opens out to the insert pocket front
surface 108 and to the pocket recess 116, between the recess floor
117 and the support surface 110. The threaded recess 118 has a
threaded recess axis T. According to some embodiments, as depicted
in the present drawings in a non-binding manner, the threaded
recess axis T is perpendicular to the insert pocket front surface
108. Alternatively, the threaded recess axis T may be angled
relative to the insert pocket front surface 108.
[0040] The lever pin 120 is located within the pocket recess 116.
The lever pin 120 has a top end 125a and a bottom end 125b and
extends along a central lever pin longitudinal axis A. At its top
end 125a, the lever pin 120 includes a tapering head portion 122,
having a rearward-facing lever head rear contact surface C. The
lever head rear contact surface C is located above the insert
pocket support surface 110.
[0041] A forward-facing lever front surface 124 extends from the
head portion 122 downwards and towards the lever pin longitudinal
axis A. At least a portion of the lever front surface 124 slopes in
the direction of the bottom end 125b at a slope angle .delta.
relative to the lever pin longitudinal axis A. The lever front
surface 124 has a lever front contact surface H, located downwards
from the lever head rear contact surface C, by a first longitudinal
distance h1. A blind hole 126 opens out to, and extends from, the
lever front surface 124, towards and generally perpendicular to the
lever pin longitudinal axis A. When the lever pin 120 is located
within the pocket recess 116, the blind hole 126 lies along the
threaded recess axis T. The blind hole 126 is preferably
non-threaded so that it can freely receive a guiding prong 134 of a
fastening member 130, as described further below.
[0042] At its bottom end 125b, the lever pin 120 includes an
enlarged base portion 121. Due to the downward sloping of the lever
front surface 124 towards the lever pin longitudinal axis A, the
base portion 121 may comprise a base recess 127 which faces the
same direction as the lever front surface 124 and is closer to the
lever pin longitudinal axis A than the lever front contact surface
H.
[0043] The lever pin 120 also includes a rocker pivot portion 128,
enabling tilting motion of the lever pin 120 in a direction
transverse to the lever front surface 124, and thus in the
forward-rearward directions D.sub.F, D.sub.R, about the rocker
pivot portion 128, against the pocket recess floor 117. Further,
the lever pin 120 also includes a rearward-facing lever lower rear
contact surface G, located downwards from the lever front contact
surface H, by a second longitudinal distance h2. The lever lower
rear contact surface G may be located formed on the base portion
121 opposite the base recess 127. The rocket pivot portion 128 may
be, for example, in the form of a rounded protrusion extending
downwardly from the base portion 121 of the lever pin 120, or in
the form of a rounded bottom of the lever pin 120, facilitating a
pivot mechanism against the pocket recess floor 117.
[0044] The fastening member 130 is further shown in a detailed
perspective in FIG. 10. The fastening member 130 has a generally
cylindrical shape, and includes a first end 131, a second end 133,
a threading surface 132, and a guiding prong 134. The threading
surface 132 extends between the first and second ends 131, 133. The
first end 131 has thereon a clamping contact surface B. The guiding
prong 134 extends from the first end 131, perpendicular to the
first end 131. The fastening member is located within the threaded
recess 118, such that the threading surface 132 engages the
threaded recess 118. In this position, the guiding prong 134 is
received within the blind hole 126 of the lever pin 120, and the
clamping contact surface B is adjacent to the lever front contact
surface H. The fastening member 130 may be engaged into the
threaded recess 118 by an appropriate screw driver or key through
the second end 133.
[0045] With reference to FIG. 8, in which a perspective view is
depicted of the cutting tool of FIG. 1, with the cutting insert 140
released and separated from the tool holder 100. In this view, the
cutting insert 140 is shown from an upwards perspective. The
cutting insert 140 includes a first surface 142, a second surface
144, a peripheral surface 146 and an insert bore 148. The
peripheral surface 146 extends between the first and second
surfaces 142, 144. The insert bore 148 has a longitudinal central
bore axis I perpendicular to the first and second surfaces 142,
144. The insert bore 148 has an insert bore rear contact surface K
on the rearward wall thereof (not shown). The insert bore 148 is a
blind bore that opens out at least to the second surface 144.
However, according to some embodiments of the disclosed technique,
the insert bore 148 may be a through bore that opens out to both
the first and second surfaces 142, 144.
[0046] The peripheral surface 146 includes at least one side
abutment surface 150, for abutting a support wall 112 of the insert
pocket 102. The view shown in FIG. 5 is taken perpendicular to the
first surface 142 and perpendicular to the intersection line 151
between the first surface 142 and the side abutment surface 150.
This view depicts that the side abutment surface 150 forms an
insert dovetail angle .alpha. with the second surface 144. In a
preferred embodiment of the disclosed technique, the insert
dovetail angle .alpha. conforms to the pocket dovetail angle
.beta.. The cutting insert 140 also includes a cutting edge 152,
formed at a portion of the intersection between the first surface
142 and the peripheral surface 146. According to some embodiments
of the disclosed technique, the cutting insert 140 includes two
side abutment surfaces 150, converging rearwards in an insert
rearward convergence angle .phi., viewed perpendicular to the first
surface 142 (FIG. 11). The insert rearward convergence angle .phi.
conforms to the support wall rearward convergence angle
.gamma..
[0047] The cutting tool 101 can be moved between a released
position and a fastened position. In the released position, the
cutting insert 140 may be either loosely located in the insert
pocket 102 of the tool holder 100 (FIG. 4), or removed completely
there from (FIG. 8). In the fastened position (FIGS. 2 and 3), the
cutting insert 140 is clamped in the insert pocket 102, due to the
clamping contact of the lever pin 120, as herein after
elaborated.
[0048] During assembly of the cutting tool 101, the cutting insert
140 is placed in the insert pocket 102, such that the insert bore
148 receives the tapering head portion 122 of the lever pin 120. As
best shown in FIG. 8, prior to installation, the tapering head
portion 122 is located above the insert pocket support surface 110,
and the lever pin 120 may tilt towards the insert pocket front
surface 108. This allows for the insert bore 148 to be placed over
the tapering head portion 122, and enable the cutting insert 140 to
fit into place in the insert pocket 102. During assembly of the
cutting insert 140, the insert bore rear contact surface K may
slide along the rear side of the tapering head portion 122 of the
lever pin 120 in the downward and rearward directions D, D.sub.R,
until the cutting insert 140 is placed on the insert pocket 102.
Thus, the cutting insert 140 may easily slide into place when the
lever pin 120 is located in various tilt positions, due to the
tapering shape of the tapering head portion 122.
[0049] With further reference to FIG. 3, the pocket recess 116 has
a pocket recess contact surface J on a rear wall 138 thereof. When
the cutting tool 101 is in the fastened position, the second
surface 144 of the cutting insert 140 abuts the insert pocket
support surface 110. The fastening member 130 is threaded through
the threaded recess 118 in the rearward direction D.sub.R, until
the clamping contact surface B presses against the lever front
contact surface H. Thus, the fastening member 130 applies a first
lateral rearward force F.sub.B,H on the lever pin 120 at the lever
front contact surface H.
[0050] It is noted that due to the lever front surface 124, the
contact area between the lever pin 120 and the fastening member 130
is minimized. Further, since at least a portion of the lever front
surface 124 slopes at the slope angle .delta. towards the lever pin
longitudinal axis A, contact is avoided between the lever front
surface 124 and the contact surface B, at locations other than at
the lever front contact surface H.
[0051] The head portion 122 of the lever pin 120 is received within
the insert bore 148, such that the lever head rear contact surface
C presses against the insert bore contact surface K. Thus, the
lever pin 120 applies a second lateral rearward force F.sub.C,K on
the cutting insert 140 at the insert bore contact surface K. In the
fastened position, the lever pin longitudinal axis A substantially
coincides with the longitudinal central bore axis I.
[0052] Further, the lever lower rear contact surface G presses
against the pocket recess contact surface J. Thus, the lever pin
120 applies a third lateral rearward force F.sub.G,J on the pocket
recess 116 at the pocket recess contact surface J. It should be
noted, that the lever pin 120 is pressed at a single surface in the
front side thereof (i.e., front contact surface H), and at two
surfaces in the rear side thereof (i.e., head rear contact surface
C and lower rear contact surface G). Therefore, a fulcrum-lever
configuration is formed on lever pin 120.
[0053] When the second lateral rearward force F.sub.C,K is applied
on the cutting insert 140, each side abutment surface 150 is
pressed against a respective support wall 112, in a dovetail
manner. Since the insert dovetail angle .alpha. conforms to the
pocket dovetail angle .beta., a firm abutment is achieved between
the cutting insert 140 and the insert pocket 102.
[0054] Upon fastening of the cutting insert 140, a normal force
F.sub.N is applied perpendicular to each side abutment surface 150,
by the respective support wall 112. As best shown in FIG. 5, due to
the insert dovetail angle .alpha. and the pocket dovetail angle
.beta., the normal force F.sub.N has a downward force component F,
pressing down on the cutting insert 140, thereby keeping the
cutting insert 140 abut against the insert pocket support surface
110. According to the geometrical arrangement of the cutting insert
140, the downward force component F is of the following magnitude:
F=F.sub.N cos .alpha..
[0055] In accordance with the present invention, viewed
perpendicular to the lever pin axis A, as best shown in FIG. 3, the
first longitudinal distance h1, between the lever head rear contact
surface C and the lever front contact surface H, is smaller than
the second longitudinal distance h2, between the lever front
contact surface H and the lever lower rear contact surface G. The
fulcrum-lever configuration on lever pin 120 yields the following
relation between the second and third lateral rearward forces
F.sub.C,K, F.sub.G,J, and the first and second longitudinal
distances h1, h2:
F C , K F G , J .about. h 2 h 1 . ##EQU00001##
[0056] Thus, if the first longitudinal distance h1 is smaller than
the second longitudinal distance h2, the second lateral rearward
force F.sub.C,K is greater than the third lateral rearward force
F.sub.G,J. It should be noted, that it is desirable that the lever
pin 120 would transfer as much as possible of the first lateral
rearward force F.sub.B,H, to the cutting insert 140, in order to
strengthen the fastening of the cutting insert 140 against the
support walls 112 during operation of the cutting tool 101.
[0057] It is noted, that in the fastened position (and thus during
operation), the cutting insert 140 makes no contact with the insert
pocket rear portion 106. Avoiding contact between the insert pocket
rear portion 106 and the cutting insert 140 is required in order to
avoid undesired direct pressure on the cutting insert in a
direction perpendicular to the cutting edge 152. Such undesired
pressure may induce breakage and accelerated damage to the cutting
edge 152, and is therefore to be avoided.
[0058] In accordance with the present invention, in a view of the
cutting insert 140, perpendicular to the central bore axis I, a
third longitudinal distance h3, between the insert bore rear
contact surface K and the second surface 144, is smaller than a
fourth longitudinal distance h4, between the insert bore rear
contact surface K and the first surface 142. It is desirable to
apply the second lateral rearward force F.sub.C,K as adjacent as
possible to the second surface 144, in order to prevent an upward
torque from acting on the cutting insert 140 during operation.
[0059] When the cutting insert 140 is to be removed from the tool
holder 100, for example when the cutting edge 152 has worn out, and
the cutting insert 140 is to be replaced, the cutting tool 101 is
moved from the fastened position to the released position.
Particular reference is made to FIGS. 4 and 6-9, depicting various
views of the released position of cutting tool 101.
[0060] The fastening member 130 is moved in the forward direction
D.sub.F through the threaded recess 118, such that the guiding
prong 134 is still partially located within the blind hole 126,
however the clamping contact surface B no longer contacts the lever
front contact surface H. The lever pin 120 is thereby free to tilt
in the forward-rearward direction D.sub.F, D.sub.R about the rocker
pivot portion 128, within the pocket recess 116. Further, the lever
head rear contact surface C no longer presses against the insert
bore rear contact surface K.
[0061] Thus, the cutting insert 140 is free to move in the forward
direction D.sub.F along the support surface 110. The cutting insert
140 may move forward until the insert bore rear contact surface K
is halted by the lever head rear contact surface C. In the released
position, the side abutment surfaces 150 are sufficiently forwardly
displaced from the support walls 112, such that the cutting insert
140 may be moved in the upward direction U until being removed
completely from the tool holder 100. During removal of the cutting
insert 140, the insert bore rear contact surface K may slide along
the tapering head portion 122 of the lever pin 120 in the upward
and forward directions U, D.sub.F, until the cutting insert 140 is
removed from the tool holder 100.
[0062] With further reference to FIGS. 6 and 7, in the released
position, the guiding prong 134 is partially located within the
blind hole 126 of the lever pin 120. Thus, the lever pin 120 is
prevented from rotating about the lever pin longitudinal axis A,
and from moving along the lever pin longitudinal axis A (i.e.,
preventing the lever pin 120 from falling out of the pocket recess
116). If the lever pin 120 starts to rotate about-, or move along,
the lever pin longitudinal axis A (e.g., if the tool holder 100 is
turned upside down), the guiding prong 134 limits the movement of
the lever pin 120 by stopping against the walls of the blind hole
126.
[0063] With further reference to FIG. 4, when the tool holder 100
is in the released position, and the cutting insert 140 is located
on the insert pocket support surface 110, the lever pin 120 tilts
forward, such that the lever pin longitudinal axis A forms a tilt
angle .theta. with the longitudinal central bore axis I.
[0064] Drawing particular reference to FIG. 9, there is depicted a
view of the insert pocket 102, perpendicular to the support surface
110, when the tool holder 100 is in the released position. The head
portion 122 of the lever pin 120 is shown to be tilted forward,
towards the insert pocket front surface 108. The pocket recess 116
has a substantially oval cross section 136, while the lever pin 120
has a substantially circular shaped cross section 123 (shown also
in FIG. 7). The oval shape of the pocket recess 116 allows for the
lever pin 120 to tilt, thereby allowing the head portion 122 to
move rearward and forward within the pocket recess 116.
Alternatively, the lever pin 120 may have an oval cross section,
with smaller dimensions than the oval cross section 136 of the
pocket recess 116, which would still allow relative movement of the
lever pin 120 within the pocket recess 116.
[0065] Although the present invention has been described to a
certain degree of particularity, it should be understood that
various alterations and modifications could be made without
departing from the spirit or scope of the invention as hereinafter
claimed.
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