Note: Descriptions are shown in the official language in which they were submitted.
ZIVl
A DRILLING UNIT
Background of the invention
The invention relates to a drilling unit with a rotat-
ably driven bored tool spindle for exchangeably receiving a
drilling tool in a tool support, the support being slightly
tiltable about an axis perpendicular to the axis of the tool
spindle. The support is reinforced by a support arm resting
on a slightly inclined wedge surface of an adjustment member
axially shiftable in the tool spindle by means of a connecting
rod.
In a known drilling unit of the type (DE-OS 2,040,020),
the drilling tool is screwed and centered on the face of the
tool support which simultaneously serves as a tool mounting
means. For an exchange, the drilling tool must be unscrewed
from the tool support. A faster or even fully automatic tool
exchange is not possible with same.
In the known fully automatic tool exchange devices, the
tool is provided with a tapered sleeve which is tightened in
a conical mounting bore of a setbolt forming an extension
of the tapered sleeve. A set of balls movable, with a tighten-
ing cage, axially along an inclined surface located in thespindle bore, pulls the setbolt inwardly when the tightening
cage is pulled rearwards by the action of a tension spring.
In order to release this tightening of the setbolt, the
tightening cage is shifted forwards by means of a connecting
rod disposed in the bored spindle, until the balls release
the setbolt.
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In the known setbolt tightening, it is necessary to pro-
vide space in the spindle bore for the elements of the setbolt
tightening mechanism; in the known drilling unit referred to
at the outset, the spindle bore for receiving the support arm,
the axially slidable adjustment member and the connecting rod
integral with the member are all necessary to provide for the
desired tilting motion of the drilling tool. Furthermore, in
the known arrangement, only the face of the tool support is
available for exchangeably mounting the drilling tool on the
tool support.
Summary of the Invention
Thus, it is an object of the invention to provide a
drilling unit of the type mentioned at the outset wherein a
fully automatic tool exchange can be effected without impair-
lS ing the tilting motion of the drilling tool or necessitatingan engagement at the forward end of the spindle for loosening
or tightening,that is, for mounting the tool.
In general, the invention combines an arrangement where-
in the drilling tool is arranged for tightening in the tool
support by means of a setbolt pull utilizing a set of balls,
disposed in a cage and movable along an inclined surface, as
the cage is shifted axially in a bore provided in the support-
ing arm. At the end of its axial stroke tilting the adjusting
member and the tool support, the connecting rod is arranged
to enter into engagement, over stop shoulder, with the
tightening cage which is otherwise maintained in its tightened
position byCmpression springs. Thus, the engagement of the rod
with the shoulder results in axial shift of the cage releasing
the setbolt.
The integers of the setbolt tightening mechanism are thus
accommodated within the interior of the supporting arm. For
actuating the setbolt tightening, the connecting rod is so
arranged that it axially shifts the adjustment member provided
with the wedging surface or surfaces. At the end of its
adjustment stroke, the connecting rod can be brought into
engagemerlt with the tightening cage of the setbolt tightening,
in order to loosen the setbolt tightening. When such engage-
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ment is again released, the setbolt returns back to itstightened state. In this way, a fully automatic tool exchange
can be achieved even in a drilling unit with a sidewise or
radially tiltable drilling tool for radial adjustment of the
cutting edge, whereby a separate actuating device for the
release of the tool is not necessary. No complex and cumber-
some engagement at the forward face of the spindle is required
for the purpose of mounting the drilling tool. At the forward
spindle end is now inserted only the exchangeable drilling
tool.
Due to the very small space requirement of the parts re-
quired for the tool tightening according to the invention, it
is further conveniently possible in a structurally very simple
way to provide in the connecting rod and in further parts
attached to the drilling tool a central coolant conduit.
Brief Description of the Drawing
Further features and advantages of the invention will
become apparent from the following description of an exemplary
embodiment with reference to the accompanying drawing showing
a partial longitudinal section of a drilling unit.
Detailed Description of a Preferred Embodiment
A bored tool spindle 1 is rotatably mounted in a housing
3 by spindle bearings 2. A rotary drive engaged at the rear
end of the tool spindle 1 is not shown in the drawing.
At the forward end of the spindle is flanged a support
ring 4 connected with a tool support 6 by means of two
mutually opposite torsion springs 5 (in the drawing displaced
by 90 within the plane of the drawing). The support 6 is
provided with a conical tool mounting bore 7. In the tool
mounting bore 7 is seated a tapered sleeve 9 connected with a
drilling tool 8. The tool support 6 is integral with a sup-
port arm 10 which rests by its slide members 11 on two
mutually opposite wedge surfaces 12, 12', also referred to
as camming surfaces.
The surfaces 12, 12' are generally linear and are
slightly inclined with respect to the longitudinal axis of the
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spindle, in the shown embodiment at an angle of 1. They are
included in an axially shiftable fork-shaped adjustment member
13. The adjustment member 13 is provided with a tubular ex-
tension 14 connected with a tubular connecting rod 15 passing
through the spindle 1 and out of the rear end for connection
to an adjustment device 16 which is shown only in a diagram-
matic way in the drawing. The connecting rod 15 can be
positioned by the device 16 at different exactly predetermined
positions.
The axial shifting of the adjustment member 13 serves
the purpose of tilting the tool support 6 about the torsion
; springs 5,(i.e. about an axis perpendicular to the plane of
the drawing) to provide a radial displacement of the cutting
tip of the drilling tool 8, for instance as follows:
- 15 When the adjustment member 13ismoved backwards from its
starting position shown in the drawing, i.e. to the right of
-^ the drawing, the tool support 6 tilts about the torsion spring
` 5 counterclockwise so that the cutting tip of the drilling
tool 8 is brought into the radially outward position required
for the drilling process. When the drilling process is
finished, the adjustment member 13 is shifted back to the
starting position shown in the drawing, whereby the cutting
tip of the drilling tool 8 is retracted radially inwardly,
away from the machined surface ready for withdrawing of the
tool out of the machined bore.
Alternatively, the drilling tool 8 can also be so
arranged that in the position shown in the drawing it drills
- into the full material thus performing the rough machining
of the bore. At the end of this working process, the tool
support 6 is tilted by rearwards pull on the adjustment mem-
ber 13, whereby the cutting tip of the drilling tool is placed
to its radially outward position. In the latter position a
fine machining of the bore can be effected on the reversed
axial motion of the rotating tool.
The described tilting of the tool support 6 with the
drilling tool 8 usually follows at the end of the machining
of each bore, i.e. often in several sequences one after the
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other, without an exchange of the drilling tool at the end of
one complete machining cycle. The axial positioning of the
adjustment member 13 can also be predetermined such as to
provide merely a slight radial adjustment of the cutting edge
of the drilling tool to compensate for the wear of the edge
and thus to maintain a close tolerance of the drilled bore.
In a bore 17 of the support arm 10 is axially shiftable
a tightening cage 18 which houses an annular row of tightening
balls 19 which, in the tightened position shown in the drawing,
hold a setbolt 20 integral with the rear end of the tapered
sleeve 9. On axial movement of the tightening cage 18 forwards,
the balls 19 move along an annular beveled or inclined surface
21 and can reach so far radially outwardly that, eventually
they become disengaged from the setbolt 20.
The cage 18 is fixedly connected with an axial tie rod 22
haying at its rear end an annular snoulder 23 on which rests
one end of compression spring means of the type of a plate spring
set 24, the other end of which engages the rear axial end of
the support arm 10. Thus, the shoulder abutment 23 forms part
which is integral with the cage 18 and thus presents an em-
bodiment of what can be generally referred to as "a part of the
tightening cage means." The spring set 24 pulls the tie rod
22 (and therewith the tightening cage 18, the balls 19 and the
setbolt 20) rearwards and thus firmly holds the tapered sleeve
9 within the conical mounting bore 7.
When the drilling tool 8 is to be exchanged or replaced,
for instance due to the excessive wear of the tool after the
machining of a number of boresor when a different drilling
tool becomes due for application, the connecting rod 15 is
shifted forwards over its position shown in the drawing (i.e.
to the left of the drawing). The connecting rod 15 now enters
at its face 15' into engagement with a rear stop or abutment
surface 23' of the abutment 23 thus shifting the tie rod 22
against the force of the spring 24 forwardly to release the
setbolt 20.
- The wedge surface 12 merges at its rear end into an
axially parallel surface 12". At the point at which the
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surfaces 15', 23' enter into mutual engagement, the upper
slide member 11 of the support arm 10 is disposed in the
region of the parallel surface 12". Further axial movement
of the connecting rod 15 ~orwards therefore does not result in
further tllt of the supporting arm 11 of the drilling tool 8.
Such further axial movement of the connectlng rod 15 merely
serves the purpose of shifting the tightening cage 18 to the
left for release of the setbolt 20, so that the drilling tool 8
with its tapered sleeve 9 and with the setbolt 20 can be
gripped by a tool exchange device on a flange 9' and exchanged,
the tool exchange device per se being well known and therefore
not being shown in the drawing.
The tool exchange takes place on standstill with the
tool spindle 1 at a predetermined angular location wherein the
drilling tool can be inserted always at the same position of
: its cutting edge relative to the wedge surfaces 12, 12' and
to the torsion springs 5. At the face of the tool spindle 1
is provided a carrier block 25 engaging a recess 26 on the
flange 9'.
The connecting rod 15 contains, in a bore 27, a
coolant conducting pipe 28 connected at a telescopic coupling
29 with the bored tie rod 22. Through a further telescopic
coupling 30, the tie rod 22 is connected with the setbolt 20,
which~similarly to the tapered sleeve 9 and to the drilling
tool 8, is provided with a central longitudinal bore. In
this way, a continuous coolant conduit is formed which extends
up to the drilling tool.
.~ Those skilled in the art will readily appreciate that
the embodiment shown in the drawing can be modified without
departing from the scope of the present invention as set
forth in the accompanying claims.
