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Патент USA US2070807

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Feb. 16, 1937.
E. G. ROEHM ‘ET AL
2,070,807
BACKLASH ELIMINATOR
Filed Oct. 20, 17933
4 Shéets-Sheet 1
awe/Mow ~
EKW/N 6‘ FOE/1M
Wm TER I. REC/0519
Feb. 16, 1937.
E. ca. ROEHM ET AL
2,070,807
BACKLASH ELIMINATOR
Filed Oct. 20, 1935
4 She'ets—Sheet 2
W1“ .
203
fRW/N 6. ROEHM
WHLTER l7. HRcHE?
Feb» 16, 193?‘,
E. 5. ROEHM ET AL
2,07,,6?
BACKLASH ELIMINATOR
Filed Oct. 20, 1933
m3
4 Sheets-Sheet S
WHLTEE 17. EEC/{E19
id, 1937
_
nae
Erwin G.
r
1m and Walter ill). Archw,
Ohio, assignors to IElie Gincati
'
chine Company, Cine
tion ol’ Ohio
Application ?ctoberw, 1933, Serial st. states
(on. soc-22)
The present invention relates to improvements
in machine tools embodying a movable table or
other support such as milling machines, and has
for an object the provision in connection with
5 such machines having feed and quick traverse
of the table or movable support thereof in either
Figure 4 is a plan view of a rack and pinion
type of feed drive embodying the back lash elimi
nator of the invention.
Figure 5 is a ‘plan view showing a worm and
worm gear vtype of drive embodyingthe means 5
of the invention. *
'
>
Figure 6 is av schematic view showing the power
direction,- of aback lash eliminator which is only .
operative and effective during thefeeding move- ' source and mechanical controls governing the di-'
ment of the table and which is ine?ective during
rection of feed-of the work supporting table, the
equally effective when said support is moved at
port to a rotary cutter, it is desirable for produc
tion purposes'to control both table movement 15
table feed clutch, and rapid traverse drive for 10
10 quick traverse movement.
'
"
Another object of the invention is to provide I the machine shown inli'igure i.
In milling machines wherein the material acted
an ei?cient back lash eliminator for: a moving
support, wherein the back lash eliminator is upon is carriediby a movablejtable or work sup,
l5 feed rate in either direction, and wherein the
production of back lash elimination tendency is
and cutter operation by automatic as well as by .
higher when the feed resistance is light, and the
manual control means‘. Furthermore, in cutting‘
port is great, and conversely, wherein the resis
ment of the engaging teeth of the cutter and
the direction of relative feed of the‘ work and cut- 2'],
ter is the sam , and also in race milling opera‘
tions wherein the surface of the work‘o‘perated
tendency to vibration and chattering of the sup- _ operations'where the direction of effective move
20 tance e?ect of the back‘ lash eliminator auto
matically decreases under conditions of ‘higher
feed resistance when vibration andchatter of the
support is reduced because of the very nature of
the cut.
25
‘
A further object of the invention is'to provide
in a machine tool, hydraulically controlled means
‘ for manually and automatically effecting desired
cycles of support operation including feed and
quick traverse movements in either-direction and
30 stops, and cooperating back lash eliminating
mechanism hydraulically and automatically ren
dered operative during feed rate movementxonly
' of the support or table.
-
-
,
An additional object of the present invention‘ is
35 the provision of a mechanism which will vimpose.
a restraint on movement of a machine. tool
support when being driven at a feed rate, and/or
when the feeding impulsion'is disconnected there
upon is unequally distributed in parts relative to -
the cutter, it is necessary to overcome the back
lash or tendency to lost motion between the sup- 2;;
vport and the actuating means therefor. This
~so-called back lash causes chattering and vibra
tion of the support and results in inaccurate
and/or “tooth-marked” work if not properly
eliminated, and jumping of Ethesuppcrt as the 30
hook-in cut becomes effective.
The milling machine 'of the presentinventlon
is adapted to accurate and speedy production op
erations of all kinds and to this end embodies a
combined automatic hydraulic .and selective man- 35
ual control for the feed and quick traverse move
ments of‘ the tablein either direction and auto
matically and hydraulically controlled back lash
, from whereby maximum accuracy of stopping or - eliminator mechanism e?ective to the necessary
40 reversing of the support is insured and tendency
to over-run due either to inertia or cutter action
counteracted.
,
~
-
"
l
'
and‘ proper degree, according to the reed resist- 40
ance to the movement of theta le.
‘
Figure 1 showsa milling machine equipped with
These and other objects are attained by the ' hydraulically operatedautomatic controls and
embodying the back lash, eliminator, of the in
means described herein‘ and disclosed in the ac
45/ companying drawings in which:
a
vention.
- >
Figure 1 is a perspective view of a milling ma
chine having the mechanism or the invention em
bodied therein. '
‘
-
'
,
I
.45
The machine consists essentially of a base l2,
column l3, having an overhanging arm ll which
, supports the free end of the cutter arbor l5. A
feed screw 16 cooperating with power. driven nuts
50 gram embodying the several automatic controls “and I8, (Figure‘3) serves toei’iect longitudinal ‘50
, movement in either direction of a sliding work
for the machine shown in Figure 1.
' Figure 3 isa plan view showing the back lash supporting table 18. 1A bracket housing 20 at
.
Figure 2 is a schematic hydraulic circuit dia
eliminator mechanism orthe invention as applied the front of the machine houses the hydraulic
' vto a rotating 'nut feedfor a sliding work support
55 in: table;
valve‘, mechanism and the combined manual and‘
> automatic control means therefor.
Control lever 55
2
2,070,807
2| projects from housing 28 and is the means
whereby the manual control of the machine is
effected. An auxiliary dog rail 22 is 'adjustably
and removably attached to the work support ta
ble l 9 and carries adjustable dogs for cooperation
with trip plungers extending from the rear of
housing 28.
Referring now to Figure 3 a pair of bearing
bosses 23 and 28 integral with bed l2 are provided.
10 with thrust bearings 25 against which the feed
nuts I‘! and I8 abut and through which the co
operating feed screw I8 extends.
'
The back lash eliminator mechanism is inter
posed in the table feed transmission just ahead
15 of the table feed device as\will later be fully ex
plained.
gear 88 will be resisted by whatever load is on
gear 85 and due to the spiral angle of the teeth,
there will be a reaction tending to shift gear 88
to the left.
This movement will cause relative .
axial movement of gear 89, which due to its
spiral being reversed to gear 88, will tend to cause
opposite rotation of gear 88 which will form a re
action to further movement and balance the
drive through the two branches.
‘
In climb cutting operations, and in face mill
10
ing operations wherein the surface of the work
operated on is unequally distributed in parts rela
tive to the cutter, the back lash or tendency to
lost motion between feed screw l8 and the drive
nuts I‘! and i8 is overcome by exerting an’ axially 15
or longitudinally directed pressure on the spool
In order to simplify the’ explanation of the ma- I 88 through the agency of hydraulic pressure ex
chine embodying the invention the feed and quick . erted on piston 93 in chamber 91. Gears 88 and . '
89 having'the teeth thereof at different degrees of
traverse transmissions for the table will be de
angularity and of opposite direction of angularity 20
20 scribed ?rst in connection with the schematic
have unequal amounts of end thrust in opposed
view in Figure 6.
'8
directions in their cooperative relation with their
As shown in Figure 6, the power from a suit
able source, such as motor 28, serves to operate respective companion gears 85 and 84, respec
the main feed drive shaft 21 through'rotatable tively. By exerting the proper amount of pres
sure axially of the spool 86,- and in a direction op 25
25 members 28 and drive band 29. The main drive
posing the greater directional end thrust of gear
shaft has a feed clutch 38 controlling the trans
mission of power through suitable gearing 8i and 88, the slight amount of clearance between the
pick-off gears 88 and 82 to'a ?nal drive shaft 32. threads of the feed screw and the threads of the
The shaft 32 drives shaft 33 through a suitable
30 reversing clutch 34 which may be alternately en
gaged to transmit clockwise or counter-clockwise
' rotation to shaft 33. An overrunning clutch 35
on shaft 32 and a gear 36 on the same shaft and
cooperating with a clutch controlled rapid trav
35 erse drive gear 31 on shaft 21 together with a
drive nuts l1 and I8 is taken up so that one nut
bears against one side face of the threads and the 30
other 'nut against the opposite side face of the
threads of the screw, and no back lash or lost
motion exists. There is thus eliminated any
tendency to chattering of the machine or unde
sired movement of the controlled support.
When the direction of rotation of spool 86 and its
gears is clockwise (viewing the gears from theright
erse clutch 4| serves to connect gear 31 to shaft hand end of Figure 3),the greater and thrust of
gear 88 is to the left hand side and the lesser end
21.
.
In the above mentioned drawings, there are thrust of gear 89 is toward the right hand side. 40
illustrated several characteristic embodiments of Under such conditions the hydraulic pressure is
the back lash eliminator of the invention, and , imposed on the left hand face of piston 93 to op
also the adaptation of one of them to the auto- ' pose the end thrust due to the steeper angle of
teeth on gear 88. If this pressure in cylinder
matic type of milling machine, the latter adapta
tion being illustrative of the utility of the back 91 is just suf?cient to overcome the tendencyto 45
and movement of gear 88, or in other words suf
lash eliminator in ‘hydraulically controlled ma
chines and of certain novel control means as well. ficient to hold gear 88 into tight driving con
tact with 85, the nut l‘l will be held advanced
Referring to Figure 3, feed nut IT has an inte
gral or attached right hand helical gear 85 with due to the angularity of the intermeshin-g spiral
the teeth thereof inclined at an angle of the teeth as far as possible, so that the nut I‘! will be 60
order of forty-four degrees (44°). The nut l8 in tight engagement with one angular side of the
has a left hand helical gear 84 integral therewith screw thread and so that any further rotation
or ?xed thereto and having the teeth thereof must cause axial movement of the screw. Due to
this condition, the gear 89 being integral with
inclined at an angle of the order of thirty-two de
gear 88, is also axially moved, but the angularity 55.
grees (32°). Gear 89 has the same ratio in num
ber of teeth to gear 84 as gear 88 has to gear of its teeth being reversed to that of gear 88,
85. Gears. 84 and 85 have an equal number of will cause reverse rotary movement of gear 84
teeth. A spool 86 is splined on hollow shaft 81 to its limit of movement so that the nut I8 is
and has ?xed gears 88 and 89 on its opposite in tight engagement with the opposite side of the
ends matching the gears 85 and 84 respectively. screw thread. It will now be seen that no back 6.0
The spool has a longitudinal slot 98 through lash exists, and an external force acting to
feed brake 13! complete the mechanical trans
mission controls of the-machine. A rapid trav
40
45
50
55
60
which a pin 9| mounted on plunger 92 may oper
ate under the in?uence of hydraulically controlled
piston 93 to exert pressure axially of the spool.
65 Gear 94 is suitably keyed to shaft 81 and is driv
cause movement of the table will be resisted by, ‘
nut l8; but at the same time the nut I1 is main
tained in a potential positive driving condition
so that at any time the external force momentar 65
ily diminishes, 'or disappears entirely, the table
power at suitable speed and direction of rotation .will still be moved at the same rate without in
through reverser shaft 33 of which shaft 98 ‘is a terruption. As a matter of fact only a certain
en by a gear 95 on shaft 98 which receives its
continuation.
‘
_
-
70 When the rapid traverse mechanism is opera
‘tlve as in shifting the work supporting table
quickly and without cutting-load, ‘piston 93 is
relieved of pressure and assumes a substantially
central or neutral position as will spool 85. Since
76 the spool is thus free to ?oat endwise, rotation of
range of hook-in cuts, such as up to a certain
depth for instance, cause this acceleration tend 70
ency of the table over the desired feed rate. But
this acceleration tendency of the cutter is not
steady and uniform but intermittent in nature,
ranging from low pressures incapable of caus
ing acceleration of the table to momentarily ex 75
3
2,070,807
tremely high pressures. Therefore, by having
one member in a driving position and the other
member in a holding back position, a uniform
feed is obtained. Should the depth of cut in
crease beyond this range due to unevenness of
the work piece, the acceleration tendency of the
cutter will not only reduce to zero but a great re—
sistance to table movement might be created so
I00. Shaft 99 in this embodiment is disposed in
termediate and parallel to the spaced parallel
shafts H2 and H5. When shaft 99 is rotated in
clockwise direction'the spool gear 90 turns gears
III and II4 counter-clockwise and the pinions
H3 and H6 turn with them for effecting relative
movement of the rack and pinion. At such times
as working conditions render elimination of back-'
that a load is thrown on the table drive. Should
this load become so great, that the axial com
lash desirable, as when cutting-,hydraulic pres
ponent of gear 88 is greater than the opposing hy
draulic pressure, then the sleeve 86 will shift
against the resistance of the hydraulic pressure
causing gear 89 to rotatably accelerate gear 80
I06 to oppose the greater end thrust of gear I09
su?iciently to restrict or limit the relative move
from a holding back or retarding position into an
intermediate or neutral position, and ?nally into
a driving position'causing nut I8 to assist the nut
il in feeding the table. Since the hydraulic
pressure is still active, it will be seen that simul
20 taneously with a decrease of table load, the sleeve
00 will shift again to move nut I8, through the
medium of gears 84 and 89, to a back lash elim
inating position. This important feature of the
invention not only makes it possible for nut I8
, to act as retarding means to eliminate back lash
but also to act automatically whenever the ne
cessity arises to assist in the actual driving of
the table. When the direction of rotation, of the
spool 86 is reversed, for the purpose of feeding
the table I 9 in the opposite direction, the greater
end thrust of gear 88 is toward the right and
hydraulic pressure is applied to the right hand
side of piston 93 to oppose this greater pressure
to prevent locking of the parts. When rapid
traverse drive of the work supporting table takes
place, no hydraulic pressure is exerted on the
sure is admitted through pressure tube I05 or 10
ment of the gears to an amount just sufficient -
to accomplish this adjustment of the pinions with
respect to the rack teeth.
In Figure 5 there is shown the adaptation of
the back lash eliminator of-the invention to a
worm and worm gear drive. In this embodi
ment the hydraulically controlled spool III has
the gears H8 and II9 thereof arranged with
the teeth in opposite and unequal angularity, for
example as explained in connection with Figures
3 and 4. Gear II8 meshes with gear I20 on shaft
I2I which carries worm I22 meshing with worm
wheel I23. Gear II9 meshes with gear I24 on '
a shaft I25 which may be parallel but not neces
sarily aligned with shaft I2I.
A pair of miter
gears I26 and IN on the shafts I25 and I28, re
spectively, serve to effect rotation of worm I29
meshing with a second worm gear, located behind -
worm I23 and therefore not shown.
Through the
proper adjustment of hydraulic pressure through
the device indicated generally at ' I30, the clear
ance between the threads of the respective worms
I22 and I29, and their intermeshing worm gears
may be adjusted according to the direction of
piston and the spool gear and the reaction of
drive in a manner which will be well understood
the drive on the gears in the absence of cutting
from the description of the backlash eliminator
in connection with Figures 3 and 4.
Referring now to the machine shown in Figure 1 40
which employs the back lash eliminator mecha
nism illustrated in Figure 3, it will be explained
in connection with Figure 2, how this eliminator
may be interconnected and operated ‘by the auto
matic hydraulic and selective manual control so 45
as to function in accordance with the different
load tends to centralize 80, and cause relatively
40 free movement of the support.
In the embodiment shown in Figure 3, which is
the form used in the machine of Figure 1, the
gears 05 and 00 are co-axial.
In the modi?ca
tions of Figures 4 and 5, it will be noted that the
corresponding gears need not be co-axial, but
that various arrangements may be had to ac
commodate the back lash eliminator to different
types of mechanism.
.
The same general arrangement can be used
50 with a rack and pinion drive, for example, as
shown in Figure 4. The back lash‘ eliminator in
this embodiment may constitute spool gear 98
splined on shaft 99 which is at right angles to a
rack I00. Shaft 99 is driven from shaft IOI
through the agency of miter gears II02 and I03.
The spool gear is subject to‘ longitudinal shift
ing by hydraulic pressure admitted to chamber
I 00 through suitably controlled pressure tubes I05
and I00 at opposite sides of piston MI. The pis
60 ton rod I08 may have connection with the slid
able spool 90 similar to that illustrated in Figure
3. The spool 90 has helical gears II09 and l I0
at the opposite ends thereof, the gear I09 having
its teeth at greater angularity than and in oppo
site direction to the teeth of gear H0. Gear
I09 is a right hand gear with the teeth preferably
cycles.
I
7
It will be understood that the feed clutch 30,
feed brake I 3I, rapid traverse clutch 4|, direc
tional reverse clutch 30 and back lash eliminator .
control piston 93 are all hydraulically actuated
through suitable pressure lines receiving oil from
an oil sump or reservoir I32 through pump. 40
and a main hydraulic pressure line I33. Valves
controlling auxiliary pressure lines to the sev
eral instrumentalities are controlled manually
through the lever 2I; and associated trip plunger
mechanisms are interconnected therewith and
subject to automatic actuation by plungers oper
able by a group of control dogs mounted on the
adjustable dog rail 22.
The pressure supply line I33 has a connection
I30 to a direction valve mechanism I35 which is
adapted for two positions wherein pressure is
passed selectively into line I36 or I31 which con
trol a hydraulically actuated piston I38 for the
disposed at an angle of about forty-four de-' directional clutch 30 which is on shaft 33. Thus
grees (44°).
Gear H0 is a left hand gear and
has its teeth disposed at an angle of approximate
70 ly thirty-two degrees (32°).
Gear i09 meshes with gear III on a suitable
journaled shaft II2 that carries drive pinion II3
meshing with rack I00.
3
Gear H0 meshes with gear IN on shaft II 5
75 and carries drive pinion IIB meshing with rack
one end or the other of the piston I38 is always
subjected to the supply pressure, while the op
posite end of the piston is connected at valve 70
I35 with one of the return lines of the sump
indicated through a triple auxiliary valve MI
with a second control valve I42. Valve I02 which
may be termed a feed and quick traverse selector
valve, has three positions corresponding respec
75
2,070,807
tively to rapid traverse, feed, and stop. The
I5I, and sump connection I62. It will now be
rapid traverse connection is. through line I43,
valve I44, and line I45’ to the rapid traverse
control 31. In the position shown the rapid trav
erse control is operative through line I43; while
line I45 to feed brake I3I, and also line I46 to
seen that the backlash eliminator piston is auto
matically subjected to pressures whenever the
feed clutch brake 300 are without pressure.
Feed
feed clutch is engaged and the rapid traverse '
clutch disengaged. Furthermore, it will be noted
that since line I43 is now a return and line I45
a pressure chamber, ?ow through lines 308 and
valve piston 3I1I is under the in?uence of its spring
3I3 will be reversed, the pressure fluid entering
line 3I3 forcing wide open the needle valve to
provide free ?ow to bore 3H, thereby shifting 10
by reason of no pressure in line I46 which com
plunger 351 to the right and actuating switch 305
municates with the opposite end of the piston.
to start the spindle motor.
When valve I52 is again shifted upwardly to its
third or stop position, the continuation I53 of
clutch 35 is of the spring opened and hydrauli
cally closed type. In the position shown, the
A branch line 332 of line I33 at this time directs
its pressure through line 303 to urge feed clutch
33 to engaged position. A by-pass 354 to the
sump is closed at this time. Further, the piston
93 of the back lash eliminator in chamber S'I
is not under pressure because line I51 is con
nected through by-pass I I8 to sump connection
I49 and line I53 from the opposite end of cham
ber 91 is connected through by-pass I5I and line
I52 through resistance I53 to sump connection
I55. Valve I55 has connections at its opposite
ends through lines I55 and I51 with lines I55
and I 31, respectively. Thus valve I55 is always
conditioned in accordance with the direction
valve I35 and with the direction clutch control
piston I38 to direct the pressures from line I52
to the proper end of cylinder 31 to cause the
back lash eliminator to act automatically in the
correct direction in accordance with the direction
of feed. An automatic spindle stop mechanism
may also be provided to act in proper coordina
tion with the back lash eliminator whereby the
spindle will be automatically stopped when the
back lash eliminator is off as when the table is
moving at'rapid traverse; and rotating when the
back lash eliminator is on as when the table is
connected to the feed mechanism. An electric
limit switch 335 is provided for starting and stop
ping the spindle actuating motor. This switch
is moved to its stop position, shown in Figure 2,
by an hydraulic actuated piston 351 through in—
tervening lever 355. Fluid pressure is supplied
45 through line 358 for shifting piston 361 to the
left, this line being connected through cannelure
359 in valve 3IE| to rapid traverse supply I63.
The fluid acting on the other’ end of piston 3511
is exhausted through bore SI I, adjustable valve
50 3I2, and line 3I3 which is connected at this time
by cannelure 3I£I in valve 3I5 to line I55 in turn
connected to exhaust at this time as previously
explained. Pressure is applied to line I52 when
valve I42 is shifted upwardly to its feed position
55 to close the rapid traverse supply line I53 and
connect the pressure supply branch I 58 of the
branch main I58 opens up pressure communica
The pressure in line I55 moves a valve piston
3M against its spring to close line 352 and at 20
the same time connect line 353 with by-pass re
turn 355 to release clutch 35 under the in?uence
of its spring. The feed clutch brake 3I3II operates
at this time to avoid overrunning of the table
movement. It will thus be seen that although 25
pressure is still on in line I55 which normally
would cause the spindle to rotate, pressure in
line I635 reverses the connection in such a man
ner that the spindle is stopped. Also it should
be noted that when valve I62 is shifted from its 30
rapid traverse position to its stop position with
out a stop at the feed position, that although the
backlash eliminator is off or ineffective during
rapid traverse, it becomes e?ective when the table
is stopped. This insures against lost motion 35
should the table be manually adjusted as for set
up purposes and that the table will be accurately
positioned. Means have been providedwhereby
the operator may selectively determine for him
self when the backlash eliminator is or is not 40
effective. In the construction thus far described,
the backlash eliminator is always e?ective during
teed regardless of direction. ‘in cases it may
only be desired when feeding in one direction
such as feeding to the left only, or ‘feeding to the 45
right only; or it may not be desired at all. These
various adjustments are effected by a rotatable
valve 3 I 5 having a pair of arcuate shaped grooves
3M5 and 3I1l of su?icient length when the valve
is in a central position to connect lines I51 and
I55 to branches 3% and 3i 5 communicating with
selector valve 323 which has two plungers MI
and 322, reciprocably mounted therein for move
ment against a spring 323. Thus when pressure
is on line I31], pressure in line 3I8 will act on 55
the end of plunger 32I to move plunger 322 to
main line through port I53, line I55, through
e?ect inter-connection between lines I55 and I55.
branch line I65, pressure reducer HM and thence
through I52 connected to the pressure reducer
60 I6 I. The amount of pressure drop may be varied
by manually adjusted cam 325 acting to vary
Likewise, when pressure is on line I35 due to
compression of spring 325 which is opposed by
the pressure acting on the upper end of the
valve plunger. If valve I55 is positioned, as
65 shown, with the line I52 communicating with
valve groove I5 I , then pressure is directed through
line I511 to the left-hand end of chamber 91, the
opposite end at this time exhausting through line
I41, by-pass I48, to sump connection H19. If
70 the direction valve I35 is shifted, then the pres
sure would be in the reverse direction, in cham
ber 91, entering through line I52, passage I48
and line I41 to the right hand end of chamber
91 and exhaust would pass from the left hand
75 end of the chamber 91 through line I50, by-pass
15
tion through port I55 to line I55, while still main
taining pressure connection to line I45 but con
necting line I53 to reservoir.
change in direction of table movement, pressure
in branch 3I3 will act on the end of plunger 322
to lift the same and interconnect line I55 with
I45. Thus, the back-lash eliminator is e?ective
in both directions of feed and in the manner
previously explained. Clockwise rotation of valve
3I5 a predetermined amount will maintain con
65
nectlon between line I31 and branch 3I8, but
will disconnect branch an from line BIG and
connect it to return line 324, thus making the
back-lash eliminator effective only in the direc
tion of feed determined by line I31.
70
counterclockwise rotation of valve M5 the same
amount will reverse the connections so that back
lash eliminator is only effective during the direc
tion of feed determinedvby line I35.
If the valve 3I5 is rotated still further beyond 75
5
aovaeov
the positions described, both branches ‘tit and
3M are disconnected from their respective cen
tral lines 3 l t and 3 l ‘l and the back-lash eliminator
is not e?ective at all.
The valves I35, HM and M2 may be operated
by means of the following mechanism:
An oscillatable and longitudinally reciprocable
sleeve M9 is provided for actuation by the manu
ally operable lever 2i. This sleeve is connected
by means of the double bell crank N33 to plungers
i355 and Ni, and in such a manner that when the
valve 035 moves in one direction the valve plung
in opposite directions and means to apply pres
sure axially of the shiftable driving member to
limit the advanced engaging relation of the said '
feed, element.
.
,
-
.3. In combination a pair of relatively movable
members, feed means to e?ect movement of one
of the members relative to the other, and com
prising a single feed element on one member and
a pair of feed elements on the other member en
gaging the feed-element on the ?rst mentioned 10
member; and anti-back lash mechanism compris
ing helical gears of opposite and unequal tooth
er Ml moves in an opposite direction. Rotary inclination respectively on said pair of feed ele
oscillation of sleeve I69 actuates through the ments, a longitudinally shiftable power actuated
pivoted lever IN the control valve plunger M2.‘ rotary spool having at'its opposite ends teeth 15
Besides being manually operated by the lever meshing respectively with the teeth of said heli
M, the sleeve “it may be automatically actuated ‘cal gears and means to exert an axially directed ,
»
by the axially movable and rotatable trip plunger pressure to said spool.
~ 4. The -combination with a-pair of relatively
ltd. An auxiliary ‘stop plunger 11% may be pro
to vided in addition to the trip plunger me for movable members, of a feed mechanism for ef 20
automatically shifting the same to a stop position. fecting relative movement between said members
This plunger may be provided‘ with a pawl ld'i and comprising a pair of rotary driven elements
pivotally mounted within a slot formed in the
carried by one of the members and a member on
plunger and urged outward by a spring pressed
pin ltd; The end of this pawl is thus held in the
the other movable member cooperating with said
pair of rotary elements, a rotating and longi 25
tudinally shiftable. spool, gear teeth at opposite
path of a shoulder 20d of a pivoted arm 285 which
carries near its free end a lug 202 which engages
in a groove 203 formed in plunger i188. Since the
form of the automatic trip mechanism for actu
ating these valves forms no part of the present
invention, further description thereof is not be
lieved to be necessary.
'
There has thus been provided an improved
mechanism for eliminating backlash from a ma
'- chine tool transmission and which may be selec
tively rendered operative or inoperative and
either automatically or manually in accordance
with the cycle of operation of the machine.
What is claimed is:
420
.
'
1. In combination with a hydraulically con
trolled machine‘tool having a movable work feed
table and hydraulically controlled power means
for effecting selected movements of said table at
selected speeds in opposite directions, of back
:l lash eliminator mechanism operative on the table
moving means at certain speeds and comprising
constantly engaging drive means including a pair
of driving helical gears of opposite and unequal
tooth angularity rotating as a unit, hydraulical
means to exert axially directed pressure to shift
said unit and a pair of independent helical gears
meshing respectively with the gears, of said unit
and driven at uniform speed thereby, the longi
tudinal shifting of the unit effecting a limited
at diii'erential rotational adjustment of said inde
pendent gears, independent feed means operable
respectively by said independent helical gears and
a feed element engaging with said pair of in
dependent feed means.
2. In combination with a pair of relatively
movable members, of a pair of rotary feed ele
ments on one of said members, a complementary
feed element on the ‘other of said members en
ends of the spool, the teeth at one end being in
clined in one direction, the teeth at the opposite
end being oppositely inclined and at a di?erent
angle of inclination from the ?rst mentioned
teeth, companion gears meshing with the teeth at
‘opposite ends of the spool, said gears effecting
movement of the respective driven rotary ele
ments, and means to exert axially directed pres
sure on the spool against the thrust of the mesh
35.
ing gears of greater teeth angularity.
5. The combination with a pair of relatively
movable members, of a feedmechanism for ef
fecting relative movement between said members
and comprising a pair of rotary driven elements
carried by one of said members and a member
on the other of said members cooperating with
said pair of rotary elements, a spool member
shiftable longitudinally and rotatable in oppo
site directions, gear teeth at opposite ends of the 45
spool, the teeth at one end being inclined in one
direction, the teeth at the opposite end being‘
oppositely inclined and disposed at a greater
angle to the spool than the ?rst mentioned teeth,
companion gears in driving relation with the re-' 50
spective rotary driven elements and with the re
spective teeth at opposite ends of the spool, the
respective series of teeth ‘at opposite ends of
the spool and their respective companion gears
exerting unequal end thrust pressure in opposite 55
directions, and means to exert axial pressure on
the spool in opposition to the greater end thrust
of the gears.
_
»
6. In a back lash eliminator the combination
with a pair of rotary driven elements, a cooperat-V
ing element engaging both said rotary driven ele
ments, means to drive the rotary driven elements
at uniform speed, said means including gears for
the respective rotary driven elements and hav
gaging with said pair of feed elements‘and back
lash eliminating mechanism whereby one'oi said ing oppositely and unequally inclined teeth and
pair of feed elements may be retained in advanced a spool member meshing at its opposite ends with C
engaging relation to the complementary feed ele-’ the respective gears provided with a means to
ment tooppose back lash between said relatively ‘exert axial pressure on said spool whereby a pre-'
determined relative movement of one ofvv said ro
movable members, and comprising a pair of hell
70
ya cal gears of opposite and unequal tooth angularity tary driven elements is e?‘ected.
7. In combination with an hydraulically con-‘ '
attached respectively to 'said pair vof feed ele
trolled machine tool having ‘relatively movable
ments, an axially shiftable driving member hav
ing gear teeth complementary to those of said work and tool supports, and power means for ef
pair of helical gears and meshing therewith, fecting said'relative movement at feed and quick
' means to selectively rotate the driving member traverse rates in opposite directions, of mecha
' 6
I 3,070,807
nism for connecting said power means with the
moving support without lost motion comprising
a pair of driving helical gears of opposite and
unequal tooth angularity rotating as a unit, hy
draulic means to exert axially directed pressure
to shift said unit, a pair of independent helical
gears meshing respectively with ‘the gears of said
unit; a lead screw connected with the support, a
pair of nut members cooperating with said lead
10 screw and respectively rotated by said independent gears whereby upon longitudinal shifting of
movement comprising a lead screw and a pair of
cooperating nut members,‘ a ?rst pair of inter
meshing helical gears for rotating one of said nut
members, a second pair of intermeshing helical
gears of opposite angularity to the ?rst pair for
rotating the second nut member, the driving
members of the gear pairs being connected to
gether‘ for rotation as a unit, means to impart
an axial thrust to said unit to effect a differential
rotational adjustment of the nut members, said 10
means operating to maintain said adjustment
said unit said independent gears will be given a ‘during rotation of the nut members by said
power mechanism, and control devices for
inate lost motion between the nut members and rendering said means ineffective during rotation
of said nut members at a predetermined one of 15
15 the lead screw, and means to render said hy
draulic means ineffective when said power means said rates of said power mechanism.
11. ‘In a machine tool having relatively mov
is adjusted to yield a quick traverse rate. ,
able work and tool supports and a power oper
8. In a machine tool having relatively mov
able mechanism for effecting said relative move
able work and tool supports, and a power oper
20 able mechanism for_ effecting relative movement ment including a feed train and a rapid traverse 20
therebetween at di?erent rates, the combination train, the combination of a ?nal drive mecha
nism including a lead screw connected to the
of means for coupling said mechanism for effect
ing said relative movement without lost motion movable support and a pair of‘cooperating nut
therebetween, comprising a lead screw connected members, one of said nut members having sur 25
faces thereon which lie in a plane which an
tothe moving support, a pair of relatively rotat
able nut members threaded on the screw and gularly intersects the axis of the nut members,
the other nut member having surfaces thereon
having integral‘ helical gears therewith, inter
but of opposite angularity, means movable par
meshing helical gears of opposite angularity re
allel to the axis of said nut members and simul
spectively movable as a unit, a ?uid operable pis
30 ton for applying an axial thrust to said‘ helical taneously engageable with said surfaces for ef 30
gear unit ‘to eliminate. back lash between said fecting a limited differential rotational adjust
cooperating nut members .and the lead screw, ment of said nut members to eliminate back lash
and means operablewhen said power mechanism in their connection with the lead screw, and
is adjusted for yieldingbne oi’ said rates to admit control devices for rendering said means effective 35
when the feed train is connected for movement
?uid pressure to said piston.
of the support and for rendering said means in
9. In a machine tool having relatively mov
able work and tool supports and a power operable effective when said rapid traverse train is con- "
mechanism for eifecting said relative movement nected for movement of the support.
12. In a machine tool having relatively mov
‘at diiferent rates, the combination of means for
40 coupling said mechanism for eifecting said move
able work and tool supports, and a reversible
power mechanism for effecting relative move
ment comprising a lead screw and a pair of co
operating nut members, a ?rst pair of intermesh .ment therebetween, the combination of means
ing helical ‘gears for rotating one of said nut for coupling ‘said mechanism for e?ecting said
members, a second pair oi.’ intermeshing helical movement including a lead screw and a pair of
45 gears of opposite angularity to the ?rst pair for ‘ cooperating nut members, said nut members hav
limited differential rotational adjustment to elim-g
2'5
t
_ rotating the second nut member, the driving ',ing inclined driving surfaces thereon of opposite
angularity, driving members for each nut mem
members of the gear pairs being connected to
‘gether with rotation as a unit, means to impart ber having cooperating angular surfaces whereby
an axial thrust to said'unit to e?ect a'di?eren _ during one direction of rotation of said nut mem
50 tial rotational adjustment of the nut members, bers a resultant thrust in one direction will be 50
produced in said driving members and upon ro
said means operating to maintain said adjust
ment during rotation of the nut members by said tation the thrust resultant will be reversed, by
power mechanism.
’
10. In a machine tool having relatively mov
55 able work and tool supports and a power opera
ble mechanism for e?ecting said relative move- .
drauiic means for opposing said resultants, and ‘
means to change the direction of pressure of said
hydraulic means simultaneously with a reversal
of said power means. -
-
ment at different rates, the combination of means
ERWlN G. ROEHM.
for coupling said in
WALTER D. ARCHEA.
- cm. for effecting said
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