This invention relates generally to the area of automated, production
line machining stations, and has to do particularly with a design for a precision
depth boring spindle for use in such machining stations.
In certain operations involving automated machines for drilling, boring
and other operations, it is desirable to be able to control and predetermine the
depth of a cut or bore hole in the workpiece, independently of the position of
the control machine which advances the cutting tool.
Conventionally, this type of boring operation has been accomplished
through the use of servo motor feed packs and gaging stations with feedback controls.
Typical of the prior art is U.S. patent 4,530,625 issued July 23,
1985 to Corley et al., and U.S. patent 4,273,481, issued June 16, 1981, also to
Corley et al. Both of these prior patents utilize a spindle stop arrangement which
is axially slidable with reset to the cutting bit, and which is such as to relieve
hydraulic pressure utilized to drive the cutting tool into the workpiece, when
the cutting bit has reached a given, predetermined depth. This is accomplished
by uncovering a hydraulic passageway, or by unseating the ball of a check valve.
Unfortunately, constructions of this type are not capable of depth tolerances as
small as 0.001 inches.
Another patent of peripheral interest is U.S. 3,516,327, issued June
23, 1970 to Wilson.
In view of the comments above, it is the object of one aspect of this
invention to provide a precision depth spindle arrangement capable of achieving
greater precision than conventional apparatus due to the fact that the spindle
stop remains at a fixed axial location relative to the cutting tool, while being
restrained against rotating therewith.
It is an object of a further aspect of this invention to provide a
precision depth spindle which does not require feedback circuitry to gage the depth
of the machined hole. More specifically, the precision depth spindle herein disclosed
can be readjusted manually and reset with hand-held gages.
More particularly, this invention provides, a precision depth spindle
a housing adapted to be moved rectilinearly in a given direction
toward a workpiece, the housing defining a first elongate, interior recess, an
elongate cartridge within said first recess, the cartridge defining a second elongate,
an elongate spindle within said second recess,
first means within the first recess mounting said cartridge
for limited axial sliding movement with respect to said housing parallel to said
second means restraining the cartridge from rotating with respect
to the housing,
third means within said second recess mounting said spindle
for rotation with respect to said cartridge about a rotary axis parallel with said
fourth means restraining axial displacement of the spindle
with respect to the cartridge,
a tool chuck fixed to one end of said spindle for movement
fifth means on the tool chuck for receiving and
supporting a cutting tool for movement with the tool chuck, such that spindle advancement
and rotation causes advancement and rotation of the cutting tool about said rotary
a spindle stop mounted to said tool chuck for rotation with
respect thereto about said rotary axis, the spindle stop having portions adapted
to contact a workpiece,
sixth means for adjusting the axial position of the spindle
stop with respect to the tool chuck,
seventh means for restraining rotation of the spindle stop
with respect to the cartridge, and
eighth means for urging the spindle and the tool chuck toward
the workpiece with respect to the housing.
One embodiment of this invention is illustrated in the accompanying
drawings, in which like numerals denote like parts throughout the several views,
and in which:
- Figure 1a shows a typical tapered tool or spot face tool;
- Figure 1b shows a portion of a workpiece and a tapering bore made by the tool
of Figure 1a;
- Figure 2a is an axial sectional view through a precision depth spindle constructed
in accordance with this invention and various parts cooperating therewith;
- Figure 2b is an end elevation of the structure shown in Figure 2a;
- Figure 3a is a schematic side elevational view of an apparatus utilizing the
precision depth spindle of this invention;
- Figure 3b is a plan view of the apparatus shown in Figure 3a;
- Figure 4a is an axial sectional view through a precision depth spindle similar
to that shown in Figure 2a, except for the drive means;
- Figure 4b is an end elevational view of the apparatus shown in Figure 4a; and
- Figure 5 is a schematic drawing of the main parts of the air pressure control
system of this invention.
Attention is first directed to Figure 1a which shows a tapered tool
generally at 10, having a cylindrical shank 12 and a frustoconical tool portion
Figure 1b shows a portion of a workpiece 16 having a tapered bore
18 of the kind that the tool shown in Figure 1a is adapted to cut.
Attention is now directed to Figure 2a which shows a precision depth
spindle apparatus generally at the numeral 20. The apparatus 20 includes a housing
22 which is elongated in the left-right direction in Figure 2a. The housing 22
may be simply a portion of a larger housing containing a number of spindles and
corresponding tools, or it may be a stand-alone housing for those applications
requiring only a single cutting tool.
The housing 22 defines a first elongate, interior recess 24 which
is preferably, though not necessarily, cylindrical. As shown, the interior cylindrical
surface of the recess 24 is outwardly stepped at 26 at the rearward (leftward)
end, and has an annular recess 28 at the forward (rightward) end. The step configuration
26 at the leftward end of the housing 22 receives a bronze liner (bushing) 30,
while the annular 28 at the rightward end receives a further bronze liner (bushing)
As seen in Figure 2a, an elongate cartridge 34 is disposed within
the recess 24 of the housing 22. The cartridge 34, in the embodiment illustrated,
has a cylindrical outer surface 36 which, at its leftward end, bears against the
bushing 30. Seals are provided at 38 for a purpose which will become apparent
At the rightward end of the cartridge 34, there is an outwardly stepped
cylindrical portion 42 which rests against the bushing 32. The portion 42 contains
two annular galleries 44 containing suitable seals 46.
The cartridge 34 is permitted a small amount of axial play with respect
to the housing 22, this play being preferably no greater than 0.125 inches. However,
the cartridge 34 is restrained against rotation with respect to the housing 22
by virtue of a recess 50 at a localized position on the outer surface 36 of the
cartridge 34, together with an anti-rotation pin 52 which extends substantially
radially through a substantially radial bore 54 through the wall of the housing
22. The pin 52 has an end 55 adapted to be received within the recess 50. The recess
50 is axially elongated to a dimension somewhat greater than the axial dimension
through the pin 52, but has a transverse dimension (i.e. perpendicular to the
drawing paper) which is only slightly greater than the equivalent dimension of the
end 55 of the pin 52, thereby to restrain the cartridge 34 against rotation with
respect to the housing 22. The pin 52 is sealed by an O-ring 53 with respect to
the bore 54.
Figure 2a further shows a spindle 56 which, in the embodiment illustrated,
has a central cylindrical exterior wall 60, which transitions to an outwardly
multiple-stepped configuration 62 at the rightward end that receives a threaded
lock nut 64 and an angular contact bearing 66. As can be seen, the hearing 66 is
trapped between the lock nut 64 and a further rightward portion 68 of the spindle.
At the rearward (leftward) end of the spindle 56, the exterior wall
60 of the spindle undergoes a plurality of inward steps such that it can receive
a radial hearing 70, locked in place by a further threaded lock nut 72.
The bearings 66 and 70 thus constitute means for mounting the spindle
56 for rotation with respect to the cartridge 34, while at the same time constraining
the spindle 56 from moving axially with respect to the cartridge 34. In other
words, the cartridge 34 and spindle 56 always remain in the same relative axial
position, and both of them are adapted to shift together (to a small degree) axially
with respect to the housing 22. Hence, the spindle 56 can rotate with respect to
the housing, and can undergo the same degree of axial movement with respect to
the housing as is permitted to the cartridge 34 by the interaction between the
pin 52 and the recess 50.
At its rightward end, the spindle 56 has a flat end face 75, an axial
leftward bore 76, and a threaded bore continuation 78 the latter being threaded
and having a smaller diameter than the bore 76.
A tool chuck 80 has a leftward, threaded cylindrical portion 82 adapted
to be tightly threaded into the threaded bore 78, and an adjacent cylindrical portion
84 adapted to achieve a snug but sliding fit in the bore 76 of the spindle 56.
Rightwardly adjacent the portion 84, the tool chuck 80 has an outwardly
annular flange 86, contiguous with a forwardly projecting, externally threaded
cylindrical portion 88. The latter then steps down to a forwardly projecting cylindrical
portion 90 with a smooth external wall.
Mounted on the threads of the portion 88 of the tool chuck 80 is a
stop adjustment collar 92.
The tool chuck 80 further has an axial cylindrical bore 94 for receiving
the shank 12 of the cutting tool 10, the latter also having a tool portion 14 as
described with respect to Figure 1a.
The shank 12 has, at its leftward end, an axial, threaded bore for
receiving an adjustment bolt 100 which threadably engages the shank 12, and is
locked there- against by a lock nut 102. The head 104 of the bolt 100 abuts the
leftward end of the bore 94. To restrain the tool 10 from rotating with respect
to the tool chuck 80, a flat 106 is provided toward the rear of the shank 12, and
a set screw 108 is threaded through a suitably threaded bore in the flange 86,
so as to abut the flat 106 and retain the cutting tool 10 in position with respect
to the tool chuck 80, and with respect to the spindle 56.
Mounted forwardly of the tool chuck 80 is a spindle stop 112 having
a generally conical configuration which includes a rearward flange 114 which encloses
an axial thrust hearing 116 that contacts the collar 92 and permits rotation of
the collar 92 with respect to the spindle stop 112.
The spindle stop 112 also defines an annular cavity 118 for receiving
a radial thrust hearing 120, the latter achieving a sliding fit over the forward
cylindrical portion 90 of the tool chuck 80.
The extreme rightward portion of the spindle stop 112 is cut or machined
away to leave two (or three) rightward projections 122, these being the projections
adapted to contact the workpiece and thus prevent the tool from further entering
Still at the rightward portion of Figure 2a, there can be seen an
annular ring 125 which has provision for three machine bolts 126 to lock the ring
125 against the forward end of the cartridge 34.
A stop retainer ring 128 is held in place by small springs under the
heads of bolts 134, and retains the spindle stop 112 with tabs 130 shown in Figure
2b as localized extensions. The flats 131 on the extensions restrain the spindle
stop from rotating. The tabs 130 also hold the stop against the thrust hearing
116. The use of springs enables adjustment of the stop's position without unbolting
the stop retainer ring 128.
It will thus be appreciated that adjustment of the collar 92 with
respect to the tool chuck 80 (by rotating the collar 92) allows an adjustment and
a pre-setting of the position of the spindle stop 112 with respect to the cutting
As seen at bottom right in Figure 2a, a further set screw 135 allows
the collar 92 to be locked into position, once the desired position has been reached.
In a preferred embodiment, each of the projections 122 has a small
axial bore 141 positioned such as to provide an orifice that will be closed by
the workpiece surface when the projections 122 come into contact with that surface.
By providing a source of pressurized air to the bores 141, and a means for monitoring
the pressure in the bores 141, a signal can be generated to indicate that the spindle
stop 112 has come into contact with the workpiece, implying that full depth of
cut has been achieved by all of the spindle arrangements being utilized.
Referring now to the leftward end of Figure 2a, it will be seen that
the spindle 56 has a cylindrical tail portion 160 on which is press-fitted a conical
member 161. A key 163 ensures that the member 161 and the spindle 56 always rotate
together. Mounted on the member 161 is a pulley 165 around which a drive belt 168
is entrained, in order to provide rotary power to the spindle 56.
Again at the leftward end of Figure 2a, a housing cap 170 is provided,
having an outer wall substantially matching that of the housing 22. The cap also
has a leftward closure end 172. The cap 170 is secured by bolts 174 to an intermediate
end cap 176 which is secured to the housing 22 by a plurality of bolts 178 at uniform
intervals around the periphery.
The spindle 56 supports an axial thrust bearing 181 against which
the rightward end of a coil compression spring 182 rests. The leftward end of the
spring 182 rests against an adjustment member 184 which slides axially in a bore
186 in the end wall 172. Adjustment of the position of the member 184 is accomplished
by rotating a threaded member 188, and locking the member 188 in position with
a lock nut 190. It will be understood that the compression coil spring 182 urges
continuously against the leftward end of the spindle 56, thus constantly urging
it to the right, which is the position in which it is shown in Figure 2a. Note
that the leftward wall of the pin 52 is in contact with the leftward end of the
recess 50 in the cartridge 34.
At the upper middle of Figure 2a, the housing 22 has a partly threaded
bore 200 through which pressurized oil or air (typical pressure of 80 psi) can
be admitted into the annular space between the housing 22 and the cartridge 34,
which will have the effect of constantly urging the cartridge 34 and spindle 56
rightwardly with respect to the housing 22. The bore 200 thus provides an alternative
to the use of the compression spring 182, for applying rightward pressure against
the spindle 56. The annular seals 38 and 46 act to seal the annular space (between
housing 22 and cartridge 34) when pressurized fluid is utilized. It is to be understood
that this apparatus would utilize either the spring 182 or pressurized fluid through
the bore 200, but not both. They are both illustrated in Figure 2a to indicate
that the user could select either one without having to alter the basic design.
The housing 22 further has a drain bore 202 communicating with the
interior of the bronze bushing 30, and a further bore 204 communicating with the
internal surface of the bronze bushing 32.
Returning to the upper portion of Figure 2a, it will be noted that
the pin 52 has a lateral slot in which a plate 206 is inserted. The plate 206 is
held against the top of the housing 22 by a machine screw 208, thereby keeping
the pin 52 in registry within the slot 50 on the exterior of the cartridge 34.
In view of the above-described construction, it will be seen that
the present design offers three alternative methods for urging the spindle 56 rightwardly
with respect to the housing 22, these being a compression coil spring, pressurized
oil, and pressurized air.
Figure 3a is a side elevational view of an assembly utilizing four
precision depth spindles as described with reference to Figure 2a. A main framework
220 supports a base 222 on which a slide unit 224 is adapted to reciprocate under
the control of a mechanical feed pack 126. Mounted on a slide unit 224 are four
housings 22, each supporting a cutting tool at the rightward end.
Figure 4a shows an apparatus which is substantially identical to that
shown in Figure 2a, with the exception that rotation of the spindle 56 is accomplished
by providing a pinion gear 230 which is keyed to the leftward end of the spindle
56, and whose teeth engage in idler gear 232 in turn driven from a drive pinion
(not illustrated), thus permitting the use of this spindle design in a multiple
spindle geared head.
Figure 4b shows, in end elevation looking axially, two precision depth
spindles in side-by-side alignment. The rightward end in Figure 4b has been broken
away, and it will be understood that the housing 22a in Figure 4b can be extended
rightwardly to receive any reasonable number of precision depth spindles.
Attention is now directed to Figure 5, which illustrates a schematic
arrangement by which the apparatus of this invention can be controlled. In Figure
5, air enters along conduit 240, arriving at a pressure regulator 242 from which
the air, now at a controlled pressure, passes through a pressure switch 244 along
a further conduit 246. The pressure switch detects changes in backpressure, and
feeds this information along an electrical conduit 248 to a programmable controller
From the pressure switch 244, air passes along a conduit 252, then
through a connector 254 which connects to the bores 141 provided in the spindle
In operation, preferably the spindle is allowed to "float" by only
about 0.125 inches.
In use, the first operation would be to clamp the workpiece (part
to be machined) in a stationary fixture at the machining station. A slide unit,
such as that illustrated schematically at 224 in Figure 3a, is mounted to travel
in a straight line in order to advance the rotating tools toward and into the workpiece
to produce the holes. The motion of the slide unit 224 is accomplished with a "feed
pack", driven by either a hydraulic cylinder, a mechanical drive unit or a servo
motor drive unit. In the case of the mechanical unit, the slide bumps into a "positive
stop" at the end of its stroke, ensuring that the slide does not overtravel and
damage the work fixture or tooling.
With the unit described herein, the design of the station will be
such that all individual spindle stops, mounted directly on the spindles (and cartridges)
will reach the workpiece when the cutting tools have reached full depth, and before
the slide unit reaches the positive stop. This arrangement has the distinct advantage
that the part print tolerance of the machined flat face, locating surface or gage
point upon which the spindle stop rests, can be large (of the order of 0.100 inches),
while all spindles have the capability of machining to within 0.001 inches depth
to achieve the accuracy required, particularly for tapered holes. This is achieved,
as mentioned above, through the use of the floating spindle (a float of 0.125 inches)
as it allows each tool to stop against the individual part surface. The importance
of this provision is due to the fact that the surface of a typical individual part
will not necessarily be perfectly planar, due to part surface tolerances.
The spindle design disclosed herein presents several advantages over
conventional machining systems, and these are as follows:
- 1. More than one spindle can be mounted to the same slide unit while maintaining
precision tooling depth (within 0.001 inches) with relation to a locating surface
on the workpiece(s). These locating surfaces may have tolerances as large as 0.100
inches to a process dimension.
- 2. The same principle design is also adaptable to a multi-spindle head, meaning
that the capability stated in point 1 above also is obtainable with a multi-spindle
head using floating spindles.
- 3. The floating spindle allows the tooling to reach full depth before the slide
unit reaches its stop.
- 4. The spindle stop is fixed to the rotating tool chuck but the stop does not
rotate, hence will not scour the workpiece.
- 5. It is not necessary to remove the tool chuck for tool change purposes.
- 6. The tool chuck incorporates a micro-adjusting collar to set the stop depth
to the tool cutting edge.
- 7. Mechanical feed packs can be used with the spindles.
- 8. Servo motor feed packs, with related gaging and feedback controls, are not
required. Hence the manufacturing cost is of the same order as a normal precision
- 9. The air/oil cartridge option offers two qualities that cannot be achieved
through use of the spring loaded cartridge. First of all, the force created by
the air/oil pressure against the cartridge is always constant, since the pressure
can be regulated to remain constant, even when the spindle is pushed back to full
depth. Secondly, the even pressure distribution around the cartridge holds the
spindle concentric to the spindle housing bores. This permits more consistent location
of machined holes.
- 10. The cartridge design permits easy removal in the event of a station rebuild.
If interior components of the cartridge become damaged with use (bearings and seals),
a spare cartridge can be substituted quickly, without disturbing the station set-up.
- 11. The spindle stop can be optionally fitted with an air detect circuit to
indicate when the tool has reached full depth. This circuit consists of small
holes drilled into the stop contact surfaces, through which pressurized air flows.
When the stop touches the part surface, the air flow is blocked, and a pressure
switch on the air line de-activates the oil/air pressure in the spindle cartridge,
to remove the thrust load on the tool. This feature will prolong tool life considerably.
While one embodiment of this invention has been illustrated in the
accompanying drawings and described hereinabove, it will be evident to those skilled
in the art that changes and modifications may be made therein, without departing
from the essence of this invention, as set forth in the appended claims.