Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates ~o collet chucks for lathes and, more
particularly, to a draw-in-co,llet chuck adapted to oe used for high
precision work in the lathe.
In prior art, it has been a common practice to use a ~
collet chuck to hold a ring-shaped work for machining. This type of chuck
is usually composed of a collet screwed into a flange secured to a lathe,
and an axially movable spindl~ wibh its ena formed with a tapered nose
adapted bo be brought into engagement with a conical wall of the colleb
whereby a holding portion of the collet is diametrically spread out,
thareby firmly holding work. With this expedient, since the holding
portion of the collet is frequently spread out by the action of the axially
movable spindle and subjected to alternating load during machining
operation, the colleb is caused to deflect so that the workpiece is held in
an oI'f-centered posi-tion. In this case, it is difficult to perform high
precision work. In the collet chuck of the type noted above, further,
since the workpiece is caused to abut against the stop or annular shoulder
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of the collet by the worker;~s hand and, under this condition, the collet .
is spread out, the worker bends to release his hand-away ~om the workpiece
~ before it is completely chucked by the collet with a resultant inaccurate
; 20 holding o~ the workpiece.
It is, therefore, an object of the present in~en-tion to provide
a new and use~ul collet chuck which can overcomes the shortcomings
encountered in the prior art.
It i9 another object of the present invention to provide a
draw-in-collet chuck adapted to hold a workpiece in a highly reliable
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manner.
It is another o~ject of the present invention to
provide a draw-in-collet chuck adapted to hold a workpiece in
an on-center position during machining operation for thereby
allowing high precision work.
i~ It is still another oBject of ~he present invention to
prov~de a draw-in-collet chuck which is rigid in construction,
easy to manipulate, and ready to be installed in anylkind of
existing lathes.
It is a further object of the present invention to
proYide a draw-in-collet chuck which is simple in construction
and low in manufacturing cost.
In accordance with one broad aspect, the invention
relates to a draw-in-collet chuck comprising: a flange body
adapted to be mounted on a machine and including a hub
extending axially from the flange body; a stationary rod
fixedly supported by said flange body in concentric relation
therewith, said stationary rod including a taperad nose
provided at one end of the rod; a collet axially movable in
concentric relation with said stationary rod and including a
chuck portion circumferentially divided into several pieces
to allow an outer diameter of the chuck portion to vary, and
a taper hole formed inside of said collet at a position
opposite to said tapered nose; and a s~opper mounted on said
hub of said flange body to limit an axial movement of a work
held by said chuck portion; said taper hole being engageable
with said tapered nose of said stationary rod when said collet
is moved toward said stationary rod, whereby the outer diameter
of the chuck portion is increased so that the chuck portion of
the collet is brought into pressured contact with an inner
periphery of the work and the face of the work is pressured
contact with said stopper; and wherein said stopper is mounted
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on said hub ~y means of an axially movable adjustment guide
whereby the position of the stopper can be adjusted.
These and other objects, features and advantages of the
present invention will become more apparent from the following
description when taken in conjunction with the accompanying
drawings, in which:
Fig. 1 is a partially cut-away view of a draw-in-collet
chuck according to the present invention
~ ig. 2 is a cross-sectional view taken on line II~
; 10 of Fig. l;
Fig. 3 is an exploded view of the collet chuck shown in
F~g. l;
Fig. 4 is a cross-sectional view showing a modified form
of the collet chuck shown in Fig. 1;
Fig. S is a cross-sectional view showing another
modifica~ion of the collet chuck shown in Fig. l; and
Fig. 6 ~s a view illustrating the size of each paxt of
a work.
Referring now to Figs. 1 to 3 of the drawings, there is
,
2Q shown a preferred embodiment of a draw-in-collet chuck
embodying the present invention. The collet chuck, generally
designated as 10, comprises a flange
1 - 3a -
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body 12 adapted to be mounted on a lathe 14, a draw-in member 16, a
s-tationary rod or sha~t 18 ~ixedly supported by the flange body 12 wi~h
the end being formed with a tapered nose 18a, an axially movable collet
- 20 adapted to hold a work A, and a stopper 22 serving as a means for
engaging with and limiting the face of the work A.
The flange body 12 has a hub 12a axially extending ~rom -the
flange bodyO The hub 12a is formed at its inner p0riphery with a threaded
portion 24 and a tapered bore 26, -to which tapèred portions 18b radially
extending ~rom the stationary rod 18 are ~itted. Threaded portions 18c o~
the stationary rod 18 screws into the -threaded portion 24 o~ the hub 12a
and, thus, the stationary rod 18 is held stationary by the hub 12a. As
best shown in Figs. 2 and 3, the circum~erentially divided tapered
portions 18b of the stationary rod 18 de~ine sector spaces 18d, through
which a circumferentially divided sleeve portion 16a o~ the draw-in
member 16 extends toward the collet 20. The le~tward end of the draw-in
; member 16 is threaded as at 16c, to threadably accommodate therein a
connecting rod (not shown) which i~terconnects the draw-in member 16 .
to a piston rod (not shown) o~ a hydraulic cylinder. Thus, the draw-in
member 16 is movable in an axial direction togebher with the piston rod
o~ the hydraulic cylinder. The sleeve portion 16a o~ the Araw-in member
16 is threaded at its end, which screws into one end of the collet 20.
In this manner, the draw-in member 16 is interconnected with the collet 20
and axially movable therewith,relative to the stationary rod 18. The collet
20 has a cylindrical section 20a slidably received in an inner bore 27 o~
the hub 12a. As shown in Pig. 3, the cylindrical section 20a has on its
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outer periphery an axially extending slot 28, with which an
end of guide screws 30 screwed into the hu~ 12a engages to
prevent rotation of the collet 20 relative to the hub 12a.
As shown in Fig. 3, the collet 20 also has a tapered section
20b and a chuck portion 20c which is circumferentially d~vided
by slits 29 to provide three sectors adapted to engage with
an inner wall of the work A as shown in Fig. 1. The chuck
portion 20c has a taper hole 32 with which the tapered nose 18a
o the stationary rod 18 engages, spreading the chuck portion
20c outward when the collet 20 is moved leftward as viewed in
Fig. 1 by the action of the draw-in ~em~er 16. Indicated as 34
is an axial projection which is provided for machining the
outer periphery of the chuck portion 20c in conormity with
the inner periphery of the work A. To this end, a ring tnot
shown) i~ placed onto the axial projection 34 to prevent the
chuck portion 20c from being spread outward and, thereafter,
the chuck portion 20c is applied with spreading force by the
action of the draw-in member 16. Under this condition, the
outer periphery of the chuck portion or section 20c is
machined. During this machining, since the stationary rod 18
is held stationary by the flange body 12 and the taper hole
32 of the chuck section 20c is caused to engage with the
tapered nose 18a of the rod 18 by the action of the draw-in
member 16, the outer periphery of the chuck section 20c is
accurately centered after it has been worked. It should be
noted that while the tapered nose 18a has been shown and
described with reference to an example in which it engages
with the taper hole 32 the taper hole 34 may be replaced with
a straight hole with which the nose 18a may engage.
The collet chuck constructed as mentioned above
will operate in
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the following manner:
The work A with its inner diameter machined in a given size
is placed over the chuck portion 20a of the collet 20 as shown in Fig. 1.
Next, the hydraulic cylinder is actuated to cause the piston rod to draw
the draw-in member 16 leftward as viewed in Fig. 1, moving the collet 20
in the same direction. In this instance, the nose 18a of the stationary
rod 18 engages with the taper hole 32 o~ the chuck portion 20c, which
is consequently spread outward with the increase ln its outer diameter.
Therefore, tha outer periphery of -the chuck portion 20c engages with the
inner periphery o~ the work A. During le~tward movement o~ the colle-k 20,
the work A is pulled in the same direction as the collet 20 a~ter it has
engaged with the work A, 90 the work 1 is moved leftward and abuts against
the s-topper 22 by which the work A is axially positioned. The work is held or
maintained in a fixed position under the above-noted condition and, hence,
, 15, axial movement of the work is prevented in a reliable manner during
machining opratio~. Thus, the outer perlphery and face of the work A can
- be easily machined in a high precision. After machining operation has ceased,
the work A is removed from the chuck 10 by moving the dra~-in member 16 and ~ .
accordingly the collet 20 rightward in ~ig. 1. It will be seen in Fig. 1
that tho stopper 22 is conneoted to an adjustment guide 36 which is threaded
over the hub 12 and axially movable to effect positioning o~ the stopper
with respect to the work A. Indicated at 38 is a lock nut which, when the
adjustment guide 36 is positioned bo a given location, is turned to lock
the adjustment guide 36.
It will now be appreciated from tha foregoing description that
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in accordance with the present invention since the work A is supported
by both o~ the stationary rod 18 and the collet 20 coi~cting with each
other, the work A is satis~actorily preventea ~rom being o~ centered
during heavy work or load. This is ensured by the hub 12a ~f the flange body
12 which is highly ~igid in constructio?n. Since~ further~ the work A is
positioned by moving the collet 20 rela-tive to the stationi~ry rod 18
~ixedly suppo~ted by the hub 12a in coaxial relationship with one another,
the work A iisi highl~ reliably fix~??d in ~n-center position. Since the
prior art collet chuck has a collet i~e`d to a flange body and adapted to
spread by the action of a movable spindle whereby the work is supported,
the collet i5 caused to deflect from its center line duriug machining
operation of a lathe. During mounting of the work onto the collet, the
movable spindle fits the collet to spread the same under a condition in
which the collet is off-centered. It is thus difficult to adjust the collet
to an on-center position and high precision work can not be obtained in
a reliable manner. In the present invention, on the contrary, since the
collet is brought to an on-center position by the tapered nose o the .
stationary rod and the work i9 adapted to be supported by both of the
collet and the stationary support during machining operation, no o~f-
centering of the collet is caused and high precision work can be attained
for a long period of time.~
Fig. 4 shows a modified form of the collet chuck shown in Figs.
1 to 3, with like parts bearing the same reference numerals as those used in ~i~ .
Figs. 1 to 3 except that a single prime ~') has been added to~the~numeral
indi~ative of a modified element. In Fig. 4, the stopper 22' is directly
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screwed into the hub 12a o~ the flange body (no$ sh~wn) and the collet 20'
is held by a holder (not shown) at a position in front of the flange body.
The collet 20' has a plurali~y of slits 29' to permit radial deflec~ion
of the chuck portion 20'c. The holder is arranged to be movable along a
S path ~para~lel~ to:l~ the axls of the stationary rod 18 fixedly supportedby the flange body so that the collet 20' is movable in concentric with
the stationary rod 18.
With~the above arrangement, the work A is placed in front of
the stopper 22' and, subsequently, the collet 20' is moved leftward as
~iewed in Fig. 4 so that the collet portion 20'c goes through the work A.
/further
When the collet 20' is moved leftward, ~he taper hole 32' engages with
the tapered nose 18a of the stationary rod 18 by which the chuck portion
20'C 18 spread outward and the outer periphery;of~the;chuck portion 20'c
is brought into pressured contact with the inner periphery of the work A.
In these instances, since the collet 20' is mo~ed leftward, the work
A is caused to abuts against the stopper 22' and the axial movement of .
the work A is prevented during Dachining operation. It will be appreciated~
that in the above noted modification the work A is held in a fixed
position by the collet and the stationary rod whereby the occurrence of
20 off-centering o~ the work A i5 gatisfactorlly preventedO In addition,
since the collet 20' is moved relative to the stationary rod fixedly
supported by the flange body during mounting of the work A onto ~he chuck,
the work A i9 fixed in a correct position at all times in an easy manner.
This illustrated modification can be utilized for automation of the machining
25 operatlon in which the work is fed to the position in front of the stopper
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22' from an upper side of the collet chuck 10' before machining and the
work is discharged downward after completion of the machining operation.
Fig. 5 shows another modification of a collet 20". In this
modification, the collet 20" has an axial extension 40 contiguous with
the chuck portion 20"c. As shown in Fig. 5~b~, each of the slits 29"
jpartially
is formed in the collet 20" and an end of the extension 40 is not split.
This type of collet is specifically advantageous in that it is suited
for extremely high precision work such as grinding.
Tests have been conducted with the use of the prior art
collet chuck and the collet chuck of the present lnvention and the test
results for the machining precision in case of turning operation of a
ring for a bearing with an outer diameter of 60 mm are compared in the
following Table I:and Table II:
Table I:
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Degree o$ Precision (Tolerance)
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Prior Art (mm) Present Invention ~mm)
Thickness deviation (A-s) 0.07 o.a3 .
Diametrical deviation (C-D) 0.05 0.02
Gradient (E-F) 0.04 0.02
Slant ~G) 0.06 0.03
Axial deviation (I-~ 0.06 0.03
Diametri~al diff. range 0.06 0.03
Axial diff. range 0.10 0.05
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Table II:
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Process . ~dvantages and degrees attained by the present invention
. in comparison with prior art
Material Reduction o cutted area , per one work
- ~ 0.1 mm
. . . Reducea wearing rate of chuck 50 %
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. . ~educed checking time period for 72 ~
watching to maintain preci~ion .
~urning - :
~10 ~ ~ Reduction in in~erlority rate~ 48
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. Reduction in working time bécaùsè of ;` ~
_ po.~sible heavy cutting ~ ; ~ 30 % ;I .
. . . ~ Reduction in grinding time :"30 % : ~
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Grinding ~ : :
. after. Reduced consumption of grinding : `~ ;~
1 turning ~ wheel and power, etc. ~ ~ 20 ~ .
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It should be noted in Table I that the test results have been
obtained by testing on 10,000 workpieces with a neglect,o dust adherence
and wear of cutting tools, etc. It should also be noted that the characters
~, B, C... indicate the size of respective parts shown in Pig. 6.
It will be appreciated from the Table I ~hat`la~collet chuck
in accvrdance with the present invention makes it possible to increase
the working accuracy to a higher ex~ent since the degree of error in size
of the machined workpiece held by the present collet chuck is about half
that attained by the prior art collet chuck. As noted in Table II, further,
since the area o~ the work to be cut i9 reduced in an actual machining
operation, the cost for materials is reduced, and the inferiority rate
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is reduced while attaining the reduction in working time.
It will thus be understood from the foregoing description
that in accordance with the present invention the collet chuck is highly
lS reliable in operation whereby a work can be accurately held in a correct
~;~ position in an ea=y fashion to perform high precision work and reduction .
in working costs.
While the present invention has been shown and described with
reerence to particular embodiments by way o~ example, it should be noted
that various other changes or modifications may be made without departing
from the scope of the present invention. For example, although the flange
body of the collet chuck has been described as being applied to the lathe,
the collet chuck of the present invention may be applied to any other
=achi~ee such as gringlng mschines.
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