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Dec. 10,1946.
H. ERNST ErAL
Y
2,412,499. v
MACHINE TOOL VIBRÀTION DAMPENER
Filed Aug. 30, 1944
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Patented Deal@ i946
Unirse STATES PATENT oil-‘Fics
2,412,499
MACHINE TOOL VIBBATION DAMPENEB,
Hans Ernst, Daniel A. Grieb,- and Michael Field,
Cincinnati, Ohio, assigner! to The Cincinnati
Milling Machine Co., Cincinnati, Ohio, a cor
poration ot Ohio
Applicaties August so, 1944, sensi No. 551,912
11 claims icl. iso-11)
Y
more particularly to an overarm vibration damp
ener for milling machines.
Y
.
One oi' the objects of this invention is to pro
vide an improved mechanism for damping and
absorbing vibration and chatter initiated by the
cutting action of the cutter and work in a mill
ing machine.
2
in instances where the outer end of the overarm
cannot be appropriately held to the machine
frame by a suitable brace. In such instances
the outer portion of the overarm lmay oscillate
This invention relates to machine tools and
rapidly under heavy cutting operations to such
an extent as to make such machining opera
tions unsatisfactory. It*is.»therefore, the pur
pose 'of this invention to provide a vibration
damping mechanism incorporated in the over
arm which is automatically effective at any time
to minimize or reduce vibrationin the overarm
structurewhen utilized as an outboard support
_ l.
Another object is to provide a milling machine
overal-m, vibration dampener .of high eillciency
and eiïective for a wide range of frequencies of
vibration..
Other objects and Aadvantages of the present
‘invention should be readily apparent by rei'er-` '
ence to the following speciilcation, considered
in conjunction with the accompanying drawing y
forming a part thereof and it is to be understoodv
for the cutter arbor so that the machine may ‘
ree :'.fly be utilizedv for high production work un
der these conditions without giving rise _to ob
jectionable chatter and vibration..
' For illustrative purposes, this invention. is
shown applied to a typical horizontal type of
that any modifications may be made in the ex
act structural details there shown and de
milling machine, Flgured, having the 'usual
scribed, within the scope of the appended claims. 20 column .l 0 on which is appropriately mounted the
work‘tableli and upon which may be placed
Without departing from or exceeding the spirit
the work W. 'I'he table H may feed the work
oi.' the invention.
»
W in the direction of the arrow i2 to a suitable
Referring to the drawing in which like refermilling cutter i3 to effect the desired machining
f ence numerals indicate like or similar parts:
Figure 1 is a vertical longitudinal section 25 operation. The milling cutter i3 is carried onl
a suitable arbor i4 which is mounted at its rear
through the overarm' and vibration damping
end in the usual cutter spindle (not shown) lof
mechanism comprising this invention.
the milling machine carried in the column I0
Figure 2 is an lenlarged transverse section*A
through the overarm and vibration damping _
_and driven by any conventional transmission
mechanism on the line 2--2 of Figure 1.
Figure 3 is a fragmentary enlarged section of
the front portion ‘oftheoverarm on the line 3-3 ‘
mechanism. The outer end of the arbor is sup
ported by means ot a suitable arbor support i5
depending from the housing or overarmil by
-me'ans of suitable guideways Il and I8 formed
of
Figure
4.
ì
,
_
l
v
y
Figure 4 is a fragmentary diagrammatic view
on the underside o! the overarm. The overann
of a.l portion of a typical milling machine to which
mounted for appropriate alignment of the
3.5 is
arbor support I! with the arbor Il and cutter
this invention may be applied; s
In machine tools in which a relative move
spindle by providing suitable dovetail guideway
surfaces I9 and 20 in the top portion of the col
ment of work and tool is provided for purposes
umn lo which .may be rigidly clamped by any
oi' effecting a machining operation, vibration and
chatter frequently are present due to the inter 40 suitable clamping means lla to the guideways
li‘l and I8 oi the overarm to securely hold its
action ot cutter and work piece. Such vibra
rearward portion lla to -the machine column
tion and chatter are particularly present in
'
milling machines, especially of the horizontal i or frame.
It can be> seen that the rear portion Ita of the
type utilizing an overarm to provide the outboard support i'or the cutter arbor driven from 45 y overarm isìthus positively held against vibration
on the machine column i0. However, the front
the cutter spindle of the machine. In such a
ward projecting .portion iSb extending out beyond
milling machine structure the intermittent in
ter-action between cutter and work due to the
the column and carrying the overarm support i5
successive presentation oi the cutting edges of
is unsupported and may be deflected transverse
the milling _cutter to the work niece during the 50 ly, as indicated by the arrow Ila, Figure 4, in vi
feeding movement frequently resultsv in inac
- bx‘atory oscillating motions perpendicular to the
curacies and chatter marks in the finished work
longitudinal axis of the overann: Such vibra
surface and damage to the cutter and the power
tion or transverse displacement ofthe overarm at
transmission of the machine if vallowed to con»
its outer end is `caused by the intermittent action
tinue unrestricted.
.
.
55 of the cutting teeth of the cutter i3 operating
It is recognized that ,in such a milling ma
against the work piece W on the work table il as
chine the outer end portion of the overarm, re
the table feeds the work to the cutter. The rate
moved from the column portion to which the
of vibration of this outer portion of the overarm
overarm is clamped to the machine frame, par
may change greatly in frequency for diiïerent
ticularly partakes of violent vibration, especialb
60 types of machining operations due both to the ,
2,412,499
3
rate of rotation of the cutter, and the character of
the material being machined. Because of this
'great variation in the frequency of vibration it is
necessary to -provide some means for absorbing
and minimizing the vibration in the overarm
which has a wide range of effectiveness.
In order to accomplish this, there is provided a
vibration damping mechanism incorporated in
the overarm comprising a mounting tube 2|
which is rigidly clamped in bores 22 and 23 by
appropriate clamping screws 24’ threaded in
clamps 25 which engage at the points 26 the in
side bore of the tube 2l so as to rigidly hold this
tube in the bores. It will be noted that the bores
22 and 23 are positioned in the overarm at its
rearward portion within the confines of the area
where it is normally clamped to the column I0
of the machine when in its extended outward po
sition from the machine column as‘shown in Fig
ure 1. Thus. the portion of the tube 2la between
the bores 22 and 23 of the overarm is rigidly held
against any movement relative to the overarm
and the machine frame.
'I'he mounting tube 2| has a portion 2lb which
projects outwardly toward the front of the ma
chine from the mounting bore 23 in the overarm
and is unsupported at its outer end so that it is
resilient and free to permit its outer end to have
transverse vibratory movements whenV acted upon
by forces created during the machining opera
tion, There is provided a suitable inertia member
or weight 24 which may be actuated in tuned fre
quencies with the frequencies of vibration of the
overarm. This weight is appropriately rigidly at
tacìhed to the outer unsupported end of the
mounting tube I2| and oscillates back and forth
with the resilient portion 2lb of 4the mounting
tube. Thus, the entire mass of the weight 24 is
supported through the resilient portion 2lb of
4
be adjusted to increase or decrease the compres
sion in the spring 32 which normally forces the
pressure spool 21 outwardly longitudinally of the
mounting tube 2l to cause the friction disc ,to
engage the transverse friction surface 29. It
is to be noted that the friction surface 29 is
parallel to the direction of transverse oscillating
vibrating movement of the overarm. By varying
number and pitch of the teeth of the cutter, the
the degree of pressure exerted by the spring 32
10 the frictional coeiiicient of relative movement be
tween the weight 24 and the overarm I6 may be
adjusted to any desired value. A suitable lock
ing set screw 38 is also preferably provided in
the threaded bore 31 to rigidly hold the set screw
15 36 in adjusted positions. A closure screw 39 may
also be provided in the friction disc 30 which may
be readily removed when making adjustments in
the set screw 36.
'
In operation„ as the cutter I3 engages the
20 work _W causing vibration to be set up in the
overarm I6, the frictional interengaging means
between the friction disc 28 and plate 30 will tend
to likewise cause the weight 24 to vibrate. How
ever, because of the slipping action between the
25 composition disc 28 and the surface 29 there will
develop a lag or out-of-phase relationship be
tween the oscillatory motions of the overarm and
the inertia member. The mounting tube and in
ertia member are so proportioned as to have a
30 natural frequency of vibration substantially the
same as the natural frequency of vibration of
the overarm so that ‘by appropriately adjusting
the set screw 36 and thereby the frictional co
efficient between the composition disc 28 and the
35 friction surface 29 the lag or out-of-phase re
lationship may be tuned so that the weight 24
will be normally oscillating in the opposite di
rection relative to the oscillation of the‘ overarm
I'o`. In this way, the energy created through the
40 frictional engagement of the disc '28 will tend
to neutralize the vibration set up in the overarm
the mounting tube 2l in the rigid supporting boresv
22 and 23 formed in the overarm i6.
'
In order_to effect a vibration damping action
between the weight 24 and the outer vibrating end
l6b of the overarm I6 there'is provided a fric
tional interengaging or damping means therebe
tween whereby vibratory oscillations in the outer
end of the overarm sets up compensating out-of
phase vibratory oscillations in the Weight 24
which tends to neutralize and minimize the am
plitude of vibration initially created in the over
arm by action of the cutter and work piece dur
ing the machining operation. This frictional in~
terconnection comprises, Figure 3, a guide sleeve
25 rigidly fixed to the mounting tube and coun
terweight 24 by screws 25a. and pin 25h. This
sleeve is provided with a bore 26 in which is ac
curately slidably mounted a pressure spool 21
having an‘enlarged outer end to which is fixed a
friction disc 28 which engages a friction surface
-`by the lcutting action. Thus, the vibration damp
ing mechanism incorporated in the milling ma
chine overarm may be readily tuned and ad
45 justed to absorb vibratory movements set up in
the overarm by the cutting action of Work and
tool.
An improved feature of this arrangement lies
in the-fact that this overarm vibration dampener
50 is effective at relatively low frequencies of vibration of the overarm. This is due to the fact that
the weight 24 is carried solely by the resilient
mounting means or tube 2l on the non-vibrating
portion I6a of the overarm which is rigidly
55 clamped to the machine frame. Thus, under con
ditions of low frequency vibration the resiliency
of the mounting means is so arranged that the
weight is not carried along by the low frequency
vibration in the overarm but tends to remain
60 in a fixed rigid position -to thereby oppose low
frequencies of Vibration set up in the overarm by
29 formed on a'suitable friction plate 30 rigidly
direct frictional opposition through the disc 28
and the surface 29. Under these conditions the
Means are provided for maintaining a prede
vibration damping mechanism serves, as an ad
termined amount of pressure longitudinally of
the mounting tube and overarm by pressure be 65 dition supplementary member to give added ri
gidity to the overarm.
tween the composition friction disc 23 and the
There has therefore been provided a vibration
friction surface 29 of the plate 30. A compression
v damping mechanism for an overarm which is
sprintf` 32 is provided which abuts against a suit
readily effective through a complete range of high.
able washer 33 bearing against the surface 34
of the weight 24 and which is conñned at its other 70 and low frequencies of vibration to damp out.
vibration and furnish added rigidity to the over
end by an‘abutment spool 35. This spool may
arm structure during the machining operation. '
be moved axially to change the degree of com
What is claimed is:
.
pression of the spring 32 by a suitable adjusting
mounted on- the overarm i6 by suitable screws 3l .
1. In a machine tool structure comprising a
in the pressure spool 21 so that the set screw may 75 main frame, a. work support on said frame, a tool
set screw 38 carried in a threaded bore 31 formed' .
2,412,499
i e
support on- said frame movable relative to said
work support for interaction of work and tool
in said machine, and vibration damping means
associated with said tool support including an »
inertia member, resilient means mounted on said -5
frame providing the sole means for supporting
said inertia member, and frictional interengaging
means between said inertia member and said
tool support to restrict relative vibrational move
ments ibetween the inertia member and tool sup
port.
'
2. In a machine tool structure comprising, a
frame, a tool support, and means for limiting
vibrational movements in said tool support rela
tive to said frame comprising a vibration damp
ing mechanism including an inertia member, re
frictienai mterengaeins means between sai-d in- '
ertia member and said housing.
'1. In an overarm structure for a milling ma
chine comprising a rectangular elongated hous
ing. means for clamping one end of said housing
to the column of the milling machine, means
providing an outboard bearing support at the
other end lof said housing, a resilient tubular
member iixed to said housing at the point of
clamping of said housing to the milling machine
column, a vibration absorbing weight ñxed to the
outer end of said tubular supporting- member, '
frictional damping means between said weight
and said housing, and‘means for adjusting the
i'rictional damping means to-vary the eñ'ective
ì frequency of vibration damping.
silient means connected to said frame providing
8. In a milling machine having a column, a
the sole means for supporting said inertia mem
work support mounted, on said column, a hori
ber, and frictional interengaging means between
zontally extending overarm clamped at one end
said inertia member and said tool support to 20 to said column, a cutter spindle in said column,
limit relative vibrational movements of said tool
vs. cutter arbor including a cutter mounted in said
support and said frame.
spindle, an arbor support depending from the
3. In a machine structure having, a main
outer end of said overarm and supporting said
frame, a work support on said frame, a tool sup
arbor, and vibration damping mechanism in said
port on said frame, an outboard supporting means 25 overarm comprising a resilient tubular mounting
for said tool support mounted on said frame, and
member extending longitudinally of said overarm
vibration damping mechanism to limit vibratory
and rigidly ñxed to said overarm at the end
motion in said outboard supporting means in
thereof clamped to said column, a weight fixed
cluding the combination of a weight, means
on the outer free end of said resilient tubular
mounted on said outboard supporting means at 30 mounting member, and an adjustable frictional
' the point of its connection with said machine
damping means between said weight and the
frame providing the sole means for resiliently
outer unclamped end of said overarm adjacent
supporting said weight, and frictional interen
said arbor support to damp out vibrational move
gaging means between said weight and said out
ments in said overarm and arbor support.
board support to damp vibratory motion in said 35 9. In a Vibration damping mechanism for a
outboard support.
milling machine overarm comprising a hollow
4. In a machine tool organization comprising
longitudinally extending body portion adapted
a frame. a work support on said frame, a tool
to be clamped at one end to a rigid portion of
support on said frame, a supplemental support
the milling machine structure and adapted at
for said tool support mounted on said frame. and 40 its other end to carry an outboard support for
vibration controlling mechanism, for said supple
a cutting tool of the machine, a vibration damp
mental support including a resilient mounting
ing weight resiliently attached to said overarm
at the point of clamping of -said overarm to said
ing weight mounted on said resilient mounting
machine structure and located adjacent the other
means, and frictions] interengaging means be x5 end thereof, and frictional damping means be
tween said weight and said supplemental support
tween said weight and said overarm, and means
ing means to damp vibrational movements in said
for effecting a variation in the frictional char
supplemental support.
acteristics of said damping means.
y5. In a milling machine having a column, a
10. In a milling machine structure including
work support, and a cutter movable relative 50 a frame and an overarm adapted to have one end
means ñxed to the said frame, a vibration damp
thereto, an overarm fixed on said column, an out
board support on :aid overarm for supporting .
said cutter, and vibration damping mechanism _
portion clamped to said frame, the combination
of an inertia member resiliently supported from
the clamped portion of said overarm in a posi
associated with said overarm including an iner
tion adjacent the free end thereof and frictional
tia member, a resilient mounting means for said 55 damping means between said overarm and said
inertia member, comprising a ilexible tubular
inertia member to transfer vibration from said
member rigidly connected to said overarm sub
overarm to said member.
stantially at the point of clamping of said over
11. In a milling machine having a column and
arm to said column, and frictional interconnect
an overarm adapted to be clamped at one end to
>ing means between said inertia member and the 60. said column, a vibration dampener for said over
outer end of said overarm to damp out relative
arm including an inertia member, means for sup
vibrational movements therein during the cutting
porting said member from the end of said over
operation oi’ the machine.
arm clamped to the column, a frictional damp
6. In an overarm structure for a milling4 ma
ing means between said member. and the outer
chine comprising an elongated hollow housing, 65 end of said overarm to cause said member to vi
means for clamping one end of said housing Ato.
brate in opposed oscillatory motion during high
the column of the milling machine, means-.spro
frequency vibration of said overarm and to act
viding an outboard bearing support at the other
as a rigid member to oppose low frequency vibra
end of said housing, a resilient tubular member
tion in said overarm by direct frictional opposi
fixed to said housing at the point of clamping
of said housing to the milling Imachine column, a
vibration absorbing inertia member ñxed to the
outer end of said tubular supporting member, and
70 tion through said damping means.
i
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'
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HANS ERNST.
,
DANIEL A. GRIEB.
,
MCHAEL ~FIELD.
4
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