Note: Descriptions are shown in the official language in which they were submitted.
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1. Field of the Invention
This invention relates to tool holder assemblies for
use in machine tools which perform various types of operations,
such as milling, drilling, boring, tapping, and the like. The
invention is particularly concerned with a tool holder assembly
of the type wherein a tool holder or chuck is secured to a rotary
spindle by a draw bar which functions to draw a tool holder into
a tight frictional engagement with a seat formed in the spindle,
and whereby the tool holder and the tool mounted thereon rotates
with the spindle.
2. Description of the prior art
It is known in the machine tool art to provide tool
holders or chucks which in turn are releasably mounted in a
rotary spindle. The tool holder generally has a conical, or
frusto-conical shank or body portion that is seated in a conical,
or frusto-conical socket or recess formed in the rotary spindle.
The tool holder is held in position by a draw bar and a tool
holder gripping means, such as a collet means. The draw bar is
axially movable with respect to the spindle, and when the draw
bar is moved inwardly, of the spindle the collet means engages
the tool holder and holds the tool holder in tight frictional
engagement with the socket formed in the spindle so that tXe tool
holder and the tool carried thereon rotates with the spindle. An
example of the last described tool holder assembly is illustrated
in U.S. patent No. 3,868,886.
The present invention resides in a machine tool having
a rotatable spindle with a bore for,ned therethrough and
wherein the spindle is provided with a tool holder seat
including an inwardly converting frusto-conical socket com-
municating with one end of the bore in spindle. The
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present invention includes a tool holder, the tool holder
having a frusto-conical shank being adapted to be operatively
mounted in the spindle socket. A plurality of self-locking
means is operatively mounted in the tool holder and is
normally in a locked position for locking the tool holder in
the spindle, the self-locking means being adapted to be moved
to an unlocked position. The self-locking means includes a
plurality of locking balls movably mounted in the tool holder
shank for radial inward and outward movement and spring biased
means for normally biasing each of the locking balls radially
outward into locking engagement with the spindle. The spring
biased means includes a plunger member engageable with each
of the locking balls and a spring means for normally biasing
the plunger member in a direction to move each of the locking
balls radially outward into locking engagement with the spindle.
The sprindle bore includes a frusto-conical inwardly
converging seat for releasable locking engagement with the
plurality of locking balls.
Other features and advantages of this invention
will be apparent from the following detailed description,
appended claims, and the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a fragmentary, longitudinal view, partly
in section~ of a machine having a tool holder assembly made
in accordance with the principles of the present invention.
Fig. 2 is a side elevation view of a retention knob
employed in the tool holder assembly illustrated in Fig. 1.
Fig. 3 is a left end elevation view of the retention
knob illustrated in Fig. 2.
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Fig. 4 is a side elevation view of a cam pin employed
in the tool holder assembly illustrated in Fig. 1.
Fig. 5 is an end view of the tool holder body employed
in the tool holder assembly illustrated in Fig. 1.
Fig. 6 is a partial, right side elevation view of the
structure illustrated in Fig. 5.
Fig' 7 is a fragmentary, elevational section view of
the self-locking ball structure employed in the tool holder
assembly illustrated in Fig. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and in particular, to
Fig. 1, the numeral 10 generally designates a self-loc~ing chuck
which is operatively mounted in a rotary machine tool spindle,
generally indicated by the numeral 11. The spindle 11 is rota-
tably mounted within a spindle head which is generally indicated
by the numeral 12. The numeral 13 generally designates a com-
bined draw bar and tool holder gripping means. The spindle head
12 comprises a body 15 in which is operatively mounted a pair of
rear and front ball bearing means 16 and 17, respectively, for
rotatably supporting the rotary spindle 11. Each of the ball
bearing means 16 and 17 includes an outer annular race 18 which
is seated in a bore 19 that extends into the spindle head of the
body 15 from the rear or left end thereof, as viewed in Fig. 1.
The front outer bearing race 18 for the front bearing means 17 is
seated against a shoulder 20 which is formed at the inner end of
the bore 19. The outer bearing races 18 are spaced apart by a
spreader ring 23 which is provided with a V-shaped cross section
and a plurality of lubricant passages 25. The rear outer bearing
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race 18 is seated against a locking ring 21 which has a threaded
outer periphery 22 that is threadably seated in a threaded bore
24 formed in the spindle body 15. The locking ring 21 functions
to retain the bearing races 18 and the spreader ring 23 in their
operative positions in the bore 19. The rotary spindle 11 in-
cludes an elongated cylindrical body 26 which extends through a
central bore 27 which is formed through the locking ring 21. The
spindle body 26 is extended forwardly through the spindle head
body 15 and extends out through an enlarged bore 28 in the front
end of the spindle head body 15.
The rear ball bearing means 16 is provided with an inner
bearing race 29 which is seated around a reducer diameter portion
30 of the spindle body 26, and it is seated against a shoulder
31. An an~ular spacer sleeve 32 is mounted around the reduced
diameter portion 30 of the spindle body 26, and it has one end
thereof disposed in an abutting relationship with the inner bear-
ing race 29. The front inner bearing race 33 is disposed on the
reduced diameter portion 30 of the spindle body 26 in a position
abutting the front end of the spacer sleeve 32. The inner bear-
ing races 29 and 33, and the spacer sleeve 32 are retained axially
in their operative positions on the spindle body 26 by a retainer
collar 34. The retainer coller 34 has a bore 36 formed there-
through which is threaded at the outer end thereof for thread-
able engagement with the threaded periphery 35 on the outer end
of the spindle body 26. As shown in Fig. 1, the numeral 38 in-
dicates the rotor portion of a conventional electric drive motor
for the rotary spindle 11. The numeral 40 designates a passage
for inserting a lubricant oil into the housingor spindle body 15
supporting the bearing means 16 and 17.
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As shown in Fig. 1, the self-locking chuck 10 includes
a cylindrical body portion 46, in the front end of which is
formed a tapered or frusto-conical tool adapter socket 41 that
is open at its outer end and adapted to receive a mating con-
ventional tool adapter, generally indicated by the numeral 42
and which carries a shaft 43 of a conventional cutting tool (not
shown). The tool holder body 46 has integrally formed on the
front end thereof a reduced diameter threaded portion 45 on which
is threadably mounted a retainer nut 44 for retaining the tool
holder 42 in place in the tapered socket 41. The numeral 48
designates a V-shaped annular slot formed in the outer periphery
of the tool holder b~dy 46 for the reception of a conventional
tool changer arm employed in machines with which the tool holder
assembly of the present invention would be used.
As shown in Figs. 1 and 6, the self-locking chuck 10
is provided with the integral, tapered or frusto-conical shank
49 which has a tapered surface 50 for a two-point seating engage-
ment with the surfaces of a pair of longitudinally spaced apart
tapered or frusto-conical sockets or seats 51 and 52 that are
formed in the front end of the spindle 11.
As shown in Fig. 1, a retention knob, generally indica-
ted by the numeral 54, is operatively attached to the rear end
of the chuck shank 49. The retention knob 54 is shown in detail
in Fig. 2, and it includes a stepped annular body, including a
threaded front end portion 55 which is threadably mounted in an
axial bore 56 formed in the rear end of the chuck shank 49.
The retention knob 54 further includes a radial extension 57
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which is of the same diameter as the outer dimension of the
threaded portion 55 so as to be slidably engaged in the outer
non-threaded portion of the bore 55, as shown in Fig. 1. The
retention knob 54 includes a radially extended annular flange
58 which has a pair of flat side faces or wrench flats 69
(Fig. 3) which are disposed diametrically opposite to each other
and which are parallel to each other. The inner side face 59 of
the flange 58 is adapted to be seated against the outer end of the
tool holder tapered shank 49, as shown in Fig. 1, when the reten-
tion knob 54 is operatively attached to the shank 49.
As shown in Fig. 2, the retention knob 54 further
includes an integral, rearwardly extended body portion 60 which
has a reduced diameter cylindrical surface that extends between
tne annular flange 58 and the inner end of an inwardly tapered
or frusto-conical collet cam surface 63. The collet cam surface 1
63 terminates at its outer end at one end of an annular shoulder
64. The retention knob 54 is provided on its outer end with an
inwardly tapered or frusto-conical surface 65 that terminates at
the transverse rear end 62 of the retention knob 54. The
numeral 61 designates the inner end of the retention knob 54.
As shown in Figs. 2 and 3, the retention ~nob S4 is provided with
an axial bore 66 which extends inwardly from the outer end 62
and which communicates at the point indicated by the numeral 68
with an enlarged axial bore 67 that extends inwardly from the
inner end of the retention knob 54.
As shown in Figs. 1 and 4, a cam pin or spring plunger,
generally indicated by the numeral 70, is provided with an elon-
gated, cylindrical shaft 71 which is slidably mounted through
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the bores 66 and 67 in the retention knob 54. The rear end of
the cam pin 70 extends outwardly beyond the outer end 62 of the
retention knob 54. Integrally attached to the front end of the
cam pin shaft 71 is a tapered or frusto-conical body portion 72
which has integrally formed on its outer side an annular shoulder
73. As shown in Fig. 1, the annular shoulder 73 on the cam pin
70 is slidably mounted within an axial bore 76 which is formed
in the tool holder shank 49. The bore 76 communicates at its
outer end with the threaded bore 56. The inner end of the bore
76 is designated by the numeral 78 and it forms a shoulder for
supporting the inner end of a compression spring 77. The outer
end of the compression spring 77 abuts the inner face 74 of the
cam pin body shoulder 73 and normally biases the cam pin or
plunger 70 outwardly of the tool holder shank 49 to the locking
position shown in Fig. 1. As shown in Fig. 1, the bore 76 com-
municates at its inner end with a reduced diameter bore 79. The
bore 79 in turn communicates with an enlarged bore 80 formed in
the tool holder body 46. The bore 80 communicates with the inner
end of the tapered tool holder socket 41.
As illustrated in Figs. 1 and 5 through 7, the tool
holder body shank 49 is provided adjacent its rear end with three
radially extended bores 84 which are equally spaced circumferen-
tially around the tapered shank 49, and which communicate with
the bore 76 at their inner ends. A locking ball 83 is movably
mounted within each of the bores 84, and it is adapted to be
engaged by the frusto-conical body portion 72 of the plunger 70.
Each of the locking balls 83 is retained in its respective bore
84, by a retainer screw, generall~ indicated by the numeral 87.
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As best seen in Fig. 7, each of the re~ainer screws 87 is pro-
vided with a threaded body 88 which is threadably mounted in a
threaded bore 89 that is disposed parallel to, but spaced from
the adjacent bore 84. Tne inner ends of the bores 89 communi-
cate with the longitu~inal bore 76 formed through the tool holder
shank 49. Each of the ball retainer screws 87 includes a screw
head 86 which has a frusto-conical or inwardly tapered side sur-
face 85 that is adapted to be seated in a conical hole 90 that
extends inwardly from the outer surface 50 of the tool holder
shank 49 and which communicates with the adjacent bore 89. The
retainer screw head surface 85 engages the adjacent locking ball
83 to retain it in the bore 84 against axial movement completely
out of the bore 84, but yet to permit an axial locking movement
of the ball 83 in the bore 84, as explained more fully hereinafter.
As shown in Fig. 1, the self-locking chuck 10 is re- i
leasably retained in the spindle 11 by a collet means, generally
indicated by the numeral 94. The collet 94 is a conventional
expandable and contractible collet, which has a body portion 105
from which longitudinally extends a plurality of radially expand-
able and contractible spring fingers 93. Each of the spring
fingers 93 is provided on the outer end thereof with an integral
enlarged portion or lug 92 which has a frusto-conical inner end
surface that engages the tapered cam surface 63 on the retention
knob 54 to retain the self-locking chuck 10 in the locked position
shown in Fig. 1, when the collet 94 is moved to the locked posi-
tion shown in Fig. 1.
In the locked position shown in Fig. 1, the outer peri-
phery of the collet lugs 92 are in slidable engagement with the
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surface of a longitudinally extended axial bore 104 in the
spindle 11 which communicates at its outer end with an enlarged
bore 95 in the spindle 11. A short tapered bore 99 in the
spindle 11 connects the outer end of the bore 104 and the inner
end of the enlarged cylindrical bore 95. The bore 99 functions
as a collet cam surface for the collet lugs 92, as explained
hereinafter. The outer end of the bore 95 is connected by a
tapered bore or frusto-conical surface 96 to the inner end of
the tapered tool holder seat 52 in the spindle 11. The outer end
of the inner tapered chuck seat 52 communicates with a radial,
outward extended recess 101 which terminates at its forward end
at an inwardly diverging tapered surface 102 in the spindle 11.
The tapered surface 102 terminates at its outer end at a tapered
bore 98 in the spindle 11. The tapered bore 98 is made to a
larger dimension than the outer taper 50 of the tool chuck 10,
so as to provide a clearance therebetween. The outer end of the
tapered bore 98 terminates at the inner end of the outer tapered
chuck seat 51. The outer tapered chuck seat 51 extends out-
wardly to the outer end of the spindle 11, as shown in Fig. 1.
When the collet 94 is moved to the right from the posi-
tion shown in Fig. 1, to a position for unlocking the chuck 10
and releasing the same from the spindle 11, the collet fingers 93
are expanded to their unstressed condition since the lugs 92 will
be moved longitudinally to the right, and will flex outwardly
and move along the tapered bore or frusto-conical surface
99 and into the enlarged cylindrical bore 95. It will be seen
that when the collet 94 is moved to the right, from the position
shown in Fig. 1, that the movement of the lugs 92 into the
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tapered bore 99 and thence into the cylindrical bore 95, will
permit the collet fingers 93 to be moved radially outward to clear
the retention knob 54 and allow it to be moved longitudinally
past the lugs 92 and out of the collet 94.
As shown in Fig. 1, a collet body 105 is movably moun-
ted in the longitudinal extended axial bore 104 which communicates
at its inner end with a reduced diameter axial bore 103. The
numeral 107 designates the elongated cylindrical body of a con-
ventional draw bar which is slidably mounted in the axial bore 103.
The outer or front end of the draw bar body 107 is provided with
a reduced diameter end portion which forms an a~mular shoulder 106
on which is seated the inner end of the collet body 105. The
collet body 105 is provided with a stepped diameter longitudinal
axial bore~lll. The reduced diameter front end of the draw bar
. body 107 is piloted in the largest diameter outer end portion of
the collet body bore 111. The collet body 105 is releasably
secured on the draw bar body 107 by a retainer assembly, gener-
ally indicated by the numeral 100. The retainer assembly 100
includes a suitable machine screw 110 which has its threaded outer
end 109 threadably mounted in a threaded bore 108 formed in the
outer end of the draw bar body 107. The collet retainer screw
110 is provided with an enlarged head 113 and an integral smaller
head 112. A plurality of suitable disc type springs 114 is
operatively mounted around the screw 110 in a position between
the inner end of the screw head 113 and the front end face 115 of
the collet body 105. A suitable disc type spring 114 is one on
the market known as a belleville washer. The springs 114 are
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under a pre-load torque. The outer end of the screw head 112
is indicated by the numeral 116, and it is adapted to engage the
outer end 117 of the spring plunger 70 when the draw bar and tool
holder gripping means 13 is activated to the right from the posi-
tion shown Fig. 1,
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for ejec~ing the tool holder 10, as described more fully
hereinafter.
In operation, the draw bar and tool gripping means
13 are actuated to the left to the solid line position shown in
Fig. 1 for retaining the tool holder 10 in an operative position
in the spindle 11. In order to eject the tool holder 10 from
the spindle 11, the draw bar and tool holder gripping means 13
are actuated to the right from the position shown in Fig. 1.
It will be understood that the draw bar body 107 may be actuated
between a tool holder locked and unlocked position by any suit-
able means for actuating the draw bar body 107 is illustrated
in U.S. patent No. 3,868,886, and another suitable means for
operating the draw bar body 107 is shown in detail in our co-
pending application entitled "HIGH SPEED SPINDLE AND DRAW BAR
ASSEMBLY", filed simultaneously herewith under Canadian Serial
No. 296,462 on February 8, 1978.
As the draw bar body 107 is moved to the right, from
the position shown in Fig. 1, the collet 94 is moved to the
right, and the collet fingers 93 are allowed to expand to their
unstressed position when the lugs 92 are moved to the right into
the enlarged cylindrical bore 95. Continued movement to the
right by the draw bar body 107 causes the outer end 116 of the
screw head 112 to engage the end 117 of the plunger shaft 71,
and to move the plunger 70 to the right, from the clamped position
shown in Fig. 1, and to compress spring 77. The draw bar body
107 continues to move the plunger 70 to the right to the unclamp-
ed position shown in broken lines wherein the plunger body is
indicated by the numeral 72a.
~t will be understood that during the time that the
plunger 70 is being moved to the unclamped position that a
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conventional tool changer arm is positioned in the V-shaped slot
48 on the tool holder body 46 in a tool holder gripping engage-
ment. Thè movement of the plunger 70 to the right to an unclamped
position permits the locking balls 83 to move radially inward and
be released from their clamped position against the tapered sur-
face 102, and the tool holder 10 is then urged outward or to the
right, as viewed in Fig. 1, by means of the action of the com-
pressed spring 77 having its outer end seated against the shoul-
der 78 in the work holder bore 76, which spring action provides
an ejection bias on the tool holder 10 to assist the aforemen-
tioned tool changer arm to axially remove the tool holder 10 from
the spindle 11.
It will be seen that the last described biased ball
locking means provides a positive retention means for retaining
the tool holder 10 in the spindle 11 in addition to the retention
function of the collet 94. The ball locking means of the pre-
sent invention provides the tool holder 10 with an inherent
- safety retention means in case of a breakage of the collet 94.
In case of a breakage of the collet 94, when the spindle 11 is
running, the spring biased balls 83 would hold the tool holder
10 in the spindle 11.
It will be seen that the two spaced apart tapered bores
or seats 51 and 52 function together to provide one overall tool
holder seat or socket for the tool holder or chuck 10~ The
spaced apart tapered bores 51 and 52 provide a two-point grip
on the tool holder 10 to prevent tilting or transverse movement
of the tool holder 10 in the spindle.
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While it will be apparent that the preferred embodi-
ment of the invention herein disclosed is well calculated to
fulfill the objects above stated, it will be appreciated that
the invention is susceptible to modification, variation and
change.
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