Machine tools abstract
A spindle unit for machine tools, with a working spindle that is
provided to accommodate a tool and is mounted so it can rotate in
a housing and is driven by a motor, and with a chucking unit with
an operating device and an internal coolant supply to the tool.
A short and compact spindle unit is created according to this invention
by the fact that the internal coolant supply is integrated into
the chucking unit and has a rotary transmission lead-through mounted
inside the operating device to convey the coolant from a stationary
supply line into the chucking unit.
Machine tools claims
What is claimed is:
1. A spindle unit for machine tools comprising:
a housing;
a motor in said housing;
a working spindle mounted for rotation in said housing, said working
spindle being driven by said motor to accommodate a tool;
a chucking unit with an operating mechanism in said housing and
coupled to said working spindle; and
supply channels in said spindle unit for providing internal coolant
to the tool;
wherein said internal coolant channels are integrated into said
chucking unit and have a rotary transmission lead-through arranged
inside said operating mechanism to convey the coolant from a stationary
supply channel into said chucking unit.
2. The spindle unit recited in claim 1 wherein said operating
mechanism is configured as a cylinder-piston unit with a cylindrical
piston arranged in an annular space between a housing part and a
cylindrical inside part, where said rotary transmission lead-through
is build into said cylindrical inside part.
3. The spindle unit recited in claim 1 or 2 wherein said rotary
transmission lead-through has a connection and a sleeve that is
pressed by coolant pressure against said connection so it is sealed.
4. The spindle unit recited in claim 3 wherein said sleeve has
a cylindrical part that opens into said supply channel and whose
end face is acted on by the coolant pressure.
5. The spindle unit recited in claim 3 wherein a wear-resistant
face seal ring and packing ring are provided on the adjacent faces
of said sleeve and said connection, respectively.
6. The spindle unit recited in claim 4 wherein a wear-resistant
face seal ring and packing ring are provided on the adjacent faces
of said sleeve and said connection, respectively.
7. The spindle unit recited in claim 3 wherein a spring for pushing
said sleeve away from said connection is provided on said sleeve.
8. The spindle unit recited in claim 4 wherein a spring for pushing
said sleeve away from said connection is provided on said sleeve.
9. The spindle unit recited in claim 3 wherein said connection
is inserted with a seal into a hollow intermediate bushing that
is screwed into the rear end of said working spindle.
10. The spindle unit recited in claim 2 wherein said piston acts
on a tie rod of said chucking unit via a thrust ring that is provided
with cylinder pins.
11. The spindle unit recited in claim 10 wherein said cylinder
pins are guided so they can move axially in matching boreholes in
an intermediate bushing.
12. The spindle unit recited in claim 10 wherein said thrust ring
is guided axially with its inside bore on a rear cylindrical shoulder
on an intermediate bushing and is secured axially by a spring ring.
13. The spindle unit recited in claim 1 wherein said motor surrounds
said working spindle concentrically and its rotor is connected to
said working spindle in a rotationally rigid mount.
Machine tools description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention generally concerns machine tools, and more particularly
relates to a spindle unit for machine tools having an internal coolant
supply to the tool integrated into the chucking unit.
2. Description of the Related Art
With traditional spindle units having an internal coolant supply,
the components to supply the coolant from stationary pipelines into
the parts of the chucking unit that rotate in machining are arranged
as a separate unit connected to the operating device. This causes
the entire spindle unit to have a considerable structural length,
which causes restrictions in the working space of the machine tool,
especially with a spindle unit that can be pivoted.
SUMMARY OF THE INVENTION
A primary purpose of this invention is to create a short and compact
spindle unit with an internal coolant supply. This purpose is achieved
according to this invention due to the fact that the internal coolant
supply is integrated into the chucking unit and has a rotary transmission
lead-through in the operating device. Because the coolant supply
is integrated into the chucking unit, an extremely compact design
of the operating mechanism and the rotary transmission lead-through
is achieved, so the structural length of the spindle unit is not
increased. Therefore, such a spindle unit is also especially suitable
for use as a swiveling spindle because the space required for swiveling
in the working space of the machine tool is normally limited.
An expedient embodiment of this invention is characterized in that
the operating mechanism is designed as a cylinder/piston unit with
a ring piston arranged in an annular space between one part of the
housing and a cylindrical inside part. The rotary transmission lead-piston.
Therefore, both the operating mechanism as well as the rotary lead-through
are arranged in an especially space-saving manner.
For a sealed transfer of cooling liquid from the stationary feed
line to the parts of the chucking unit that rotate in machining,
the rotary lead-through preferably has a connection to the rotating
parts and a sleeve that is pressed tightly by the coolant pressure
against the connections opening into the feed line. Preferably a
face seal ring and a packing ring made of a wear-resistant material
are provided on the adjacent faces of the sleeve and the connection.
The coolant pressure acts on the rear face of the sleeve facing
the feed line when machining with an internal supply of coolant,
pressing the sleeve against the connection. This yields an advantageous
seal between the sleeve and the connection. In machining without
a coolant, no pressure acts on the rear face of the sleeve so it
is pressed away from the connection by a spring when no coolant
pressure acts on the sleeve in an appropriate embodiment. As a result,
the rings of the axial face seal provided on the adjacent faces
of the connection and the sleeve rub against each other only when
an internal coolant supply is needed and therefore a sealing connection
is required. This prevents excessive wear between the two rings.
The force is transmitted from the piston to the tie rod of the
chucking unit in an advantageous manner via an axially displaceable
thrust ring to which cylinder pins that act on the chucking unit
are attached. The cylinder pins are guided in the corresponding
boreholes in an intermediate bushing that is screwed into the rear
end of the working spindle.
An especially compact design of the spindle unit is achieved by
the fact that it is designed as a motor-driven spindle. The spindle
is surrounded concentrically by the motor whose rotor is rotationally
connected to the working spindle.
BRIEF DESCRIPTION OF THE DRAWING
The objects, advantages and features of the invention will be more
readily understood from the following detailed description, when
read in conjunction with the accompanying drawing, wherein:
FIG. 1 is a longitudinal section through a preferred embodiment
of a spindle unit constructed according to this invention; and
FIG. 2 is an enlarged sectional diagram of the operating mechanism
of FIG. 1 for the chucking unit with an integrated coolant supply.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In both figures, the chucking unit integrated into the spindle
unit is shown in the released position in the left half of the figure
and in the chucked position in the right half of the figure.
Spindle unit 1 illustrated in FIG. 1 is part of a universal machine
tool and includes working spindle 2 that is designed as a hollow
shaft and is mounted so it can rotate in two bearing caps 5 6 of
spindle housing 7 by means of bearing arrangement 3 4. Working
spindle 2 is driven by drive motor 8 that is mounted in spindle
housing 7 between bearing caps 5 6 and whose rotor 9 surrounds
the working spindle concentrically and is rotationally connected
to it.
Spindle unit 1 contains chucking unit 11 with operating mechanism
12. Chucking unit 11 includes hollow work-holding bushing 13 that
is mounted on the front end of tie rod 16 that is provided with
through hole 14 and is prestressed by disk spring package 15. Grippers
17 that can pivot laterally are provided on the front end of work-holding
bushing 13 and are pressed inward in the chucked position by projection
18 on the inside wall of working spindle 2 to engage in a matching
groove in a tool or a tool receptacle. Disk spring package 15 is
supported on one side on ring shoulder 19 in the working spindle
and on the other side on a collar 20 on the rear area of tie rod
16.
As shown especially in FIG. 2 operating device 12 is designed
as a hydraulic cylinder-piston unit that is accommodated in housing
part 21 mounted on rear bearing cap 6. The end of housing part 21
that is open to the rear is closed by sealing cap 22 that has connecting
flange 23 which is in contact with the rear face of housing part
21 and has cylindrical inside part 24 that projects into housing
part 21. The cylindrical surface of cylindrical inside part 24 borders
with the inside wall of housing part 21 annular space 25 in which
cylindrical piston 26 is mounted so it can be displaced axially.
Piston 26 has front area 27 that faces working spindle 2 and has
a smaller outside diameter plus rear area 28 that has a larger outside
diameter. Annular end face 29 at the transition between these areas
serves as a piston face for pressure acting on piston 26 in the
direction of insertion. Housing part 21 has fluid channel 30 leading
to annular end face 29. Rear end face 31 of area 28 forms the piston
face for pressure to act on the piston in the direction of extraction.
Fluid channel 32 in connecting flange 23 leads to end face 31. The
inside wall of housing part 21 has ring shoulder 33 against which
ring-shaped end face 29 comes to rest in the completely extracted
position of piston 26. In rear area 28 of piston 26 there are sealing
elements 34 to seal piston 26 with respect to housing part 21 and
cylindrical inside part 24. Gasket 35 provided in housing part 21
rests against the outside of front area 27 of piston 26.
When extracted, piston 26 presses against axially displaceable
thrust ring 36 to which are attached cylinder pins 37 that act on
tie rod 16. Cylinder pins 37 are screwed into matching threaded
boreholes in thrust ring 36 by threaded pins 38 on the rear and
their front faces 39 are in contact with rear ring collar 40 on
tie rod 16. On the outside circumference, cylinder pins 37 are inserted
into boreholes 41 in intermediate bushing 42 that is in turn screwed
into the rear end of working spindle 2. Thrust ring 36 with its
inside bore 44 is guided axially on rear cylinder shoulder 43 of
intermediate bushing 42 and is axially secured by a spring ring
arranged on the end of cylinder shoulder 43. Intermediate bushing
42 has stepped through-hole 46 in whose front area, which has a
larger inside diameter, cylindrical end piece 47 of tie rod 16 is
guided axially so it provides a seal. Hollow connection 48 of rotary
transmission lead-through 49 is pressed into the rear area of through-hole
46 with the smaller inside diameter.
Rotary transmission lead-through 49 serves to conduct a coolant
under pressure from stationary supply line 50 into chucking unit
11 which rotates when machining with working spindle 2 and allows
the coolant to flow to a coolant channel running through the tool.
Supply line 50 for the coolant is also arranged in connecting flange
23 and leads to an inlet to rotary transmission lead-through 49.
To supply coolant in a sealed system, rotary transmission lead-through
49 has packing ring 51 that is secured on the rear face of connection
48 and is in contact with face seal ring 52 on the front face of
enlarged disk-shaped part 53 of axially movable sleeve 54. Packing
ring 51 and face seal ring 52 are preferably made of ceramics. Sleeve
54 with its rear cylindrical part 55 is guided axially in a matching
borehole in receptacle bushing 56 and sealed by ring gasket 57.
Part 53 which is enlarged in the form of a disk of sleeve 54 is
accommodated in enlarged section 58 and is acted on by spring 59
in the direction of separating the face seal ring and the packing
ring. To center sleeve 54 and prevent it from turning, centering
pins 60 are secured in receptacle bushing 56 on which disk-shaped
enlarged part 53 is guided displaceably through appropriate boreholes
61.
Receptacle bushing 56 is mounted by screws 62 in matching recess
63 and is sealed by ring gasket 64 on the inside of sealing cover
22. Sealing ring 65 with gasket 66 is provided on the face of sealing
cover 22 facing working spindle 2.
The coolant is introduced into spindle unit 1 through supply line
50 and enters the inlet of rotary transmission lead-through 49.
The coolant pressure acts on rear face 67 of sleeve 54 and thus
presses face seal ring 52 on the front end of sleeve 54 against
packing ring 51. This yields a tight connection between sleeve 54
which is prevented from turning and connection 48 of rotary transmission
lead-through 49 which rotates with working spindle 2 in machining.
Coolant enters hollow tie rod 16 through hollow connection 48 and
the through-hole inside of intermediate bushing 42 and goes from
there to the tool through work-holding bushing 13. If no coolant
is supplied, no coolant pressure acts on rear face 67 of sleeve
54 so the sleeve is moved away from connection 48 by spring 59
and face seal ring 52 is moved away from packing ring 51. The result
is that the packing ring and the face seal ring rub against each
other only when an internal coolant supply is needed and therefore
a sealed connection is required. This minimizes the wear on the
face seal ring and the packing ring.
External teeth 68 are provided on the outside circumference of
intermediate bushing 42 so a rotary transducer engages with these
teeth to detect the position of the working spindle. Furthermore,
position switch 69 for detecting the position of the tool clamping
device is provided on the outside of housing part 21 so it faces
the cylindrical surface of thrust ring 36.
To release the tool, piston 26 is acted on by a hydraulic fluid
through fluid channel 32 causing it to move out of the chucked
position illustrated in the right half of FIG. 2 into the released
position illustrated in the left half of the figures. Piston 26
pushes tie rod 16 forward over thrust ring 36 and cylinder pins
37 in other words, it pushes down in FIG. 2 thus compressing disk
spring package 15. Thus the work-holding bushing 13 is moved downward,
and grippers 17 enter an enlarged area where they are spread outwardly
over the springs and release the tool.
To chuck the tool, fluid channel 30 is put under pressure, where
piston 26 moves out of the released position into the chucked position
and tie rod 16 with work-holding bushing 13 is pulled into working
spindle 2 under the influence of disk spring package 15. Grippers
17 are also pressed inward and engage in the ring groove on a tool
(not shown) inserted into working spindle 2. Piston 26 travels inward
to the extent that its front face is a distance away from thrust
ring 36 in the chucked position. This prevents the thrust ring,
which rotates together with working spindle 2 in machining, from
rubbing against piston 26 and thus causing wear.
In view of the above description, it is likely that modifications
and improvements will occur to those skilled in this technical field
which are within the scope of the invention. Accordingly, this invention
is to be limited only by the spirit and scope of the appended claims
and equivalents thereto. |