Arrangement for mounting a power-operated clamping device on a machine-tool spindle

An arrangement for mounting a power-operated clamping device for workpieces or tools on a hollow machine-tool spindle in which is disposed a securing rod that is adapted to be coupled with a drive member of the respectively mounted clamping device, and that is adapted to be actuated by a hydraulic or pressurized cylinder secured to the rear end of the spindle. Secured to a flange on the front end of the spindle is an intermediate ring to which the body of the clamping device is adapted to be secured via at least two securing pins. To provide a structurally straightforward design that requires no additional pressure medium cylinder, the securing pins are secured to the clamping device body and are axially oriented, with each securing pin being provided with a notch that has a tightening surface. Key rods are displaceably guided in the intermediate ring, with each key rod having a key that is introducible into a respective notch of the securing pins. A bayonet ring is rotatably yet axially non-shiftably mounted on a front end of the securing rod and is adapted to cooperate with a bayonet flange formed on the drive member of the clamping device, with the bayonet ring being provided with an external tooth construction that meshes with a tooth construction on at least one of the key rods.

BACKGROUND OF THE INVENTION 
The present invention relates to an arrangement for fixing or mounting a 
power-operated clamping device for workpieces or tools on a hollow 
machinetool arbor or spindle in which is disposed a spreader or securing 
rod that is adapted to be coupled with a drive member of the respectively 
mounted clamping device, and that is adapted to be actuated by a hydraulic 
or pressurized cylinder secured to a rear end of the spindle, with a front 
end of the spindle being provided with a flange to which is secured an 
intermediate ring to which a body of the clamping device is adapted to be 
secured via at least two securing bolts or pins, with the clamping device 
being centered on the intermediate ring via central conical surface means. 
An arrangement of this general type for mounting a power-operated clamping 
device on the front end of a hollow machine-tool spindle is disclosed, for 
example, in German Patent No. 33 28 291. With this known arrangement, 
radially oriented securing pins are mounted in the intermediate ring that 
is secured to the flange of the spindle. Draw-in or tightening surfaces of 
the securing pins engage in an annular groove that is formed in a flange 
ring, which in turn is secured to the body of the clamping device. To 
center this flange ring relative to the intermediate ring that is secured 
to the flange of the spindle, central conical surfaces are formed both on 
the flange ring and on the intermediate ring. Actuation of the securing 
pins is effected by pistons that are connected to the securing pins, with 
pressure medium being supplied to the pistons via lines that extend in the 
spindle. 
Furthermore, in order to provide for an automatic rapid exchange of 
clamping devices on machine-tool spindles it is necessary to be able to 
rapidly detachably couple the drive member of the respectively mounted 
clamping device with the securing rod that is disposed in the hollow 
machine-tool spindle, so that the respectively mounted clamping device can 
be actuated by the pressure medium cylinder that is secured to the rear 
end of the spindle. With the embodiment known from the aforementioned 
German Patent No. 33 28 291, this coupling is effected via a coupling head 
that is disposed on the securing rod and that has distributed over the 
periphery radially outwardly directed coupling cams that cooperate with 
radially inwardly projecting coupling projections of a coupling adapter 
that is in turn disposed on the drive member of the respectfully mounted 
clamping device. In a rotational position of the securing rod that 
corresponds to the uncoupled state, the coupling head, with its coupling 
cams, can be introduced axially into the coupling adapter between the 
coupling projections. By rotating the securing rod the coupling cams pass 
behind the coupling projections, so that in this position the drive member 
of the clamping device is positively connected with the securing rod that 
can be actuated by the pressure medium cylinder. In order to rotate the 
securing rod between the two end positions, namely the uncoupling position 
on the one hand and the coupling stage on the other hand, in addition to 
the axial piston cylinder that actuates the drive member of the mounted 
clamping device, the heretofore known arrangement is provided with a 
rotary piston cylinder that is disposed at the rear end of the 
machine-tool spindle. 
The known arrangement of the aforementioned German Patent No. 33 28 291 has 
various drawbacks. On the one hand, the rotary piston cylinder that is 
necessary for the coupling process between the securing rod and the drive 
member of the clamping device is technically complicated and represents an 
additional loading of the machine-tool spindle. In addition, this rotary 
piston cylinder precludes an overall hollow configuration for the securing 
rod, so that no rod-like workpieces can be supplied through the 
machine-tool spindle to the respectively mounted clamping device. 
Furthermore, due to the radial orientation of the securing pins, a large 
bulky arrangement that extends out quite far radially results not only for 
the intermediate ring but also in particular for the flange ring that 
provides the annular groove for the securing pins, so that this heretofore 
known construction is very heavy and has a high flywheel mass. 
A further clamping arrangement disclosed in German Offenlegungsschrift 30 
45 536 has similar drawbacks. This arrangement also has radially oriented 
securing pins for securing the body of the clamping device on the spindle 
flange. However, with this arrangement the interlocking between the drive 
member of the clamping device and the securing rod that extends in the 
spindle is effected via balls that are held in recesses of the securing 
rod and that can be actuated via an additional actuation rod that is 
guided in the hollow securing rod in such a way that they enter in 
corresponding, spherical segment-like recesses of a coupling member that 
is connected with the drive member. 
With the arrangement disclosed in the aforementioned German 
Offenlegungsschrift 30 45 536, not only for the actuation of the radial 
securing pins via wedge surfaces, but also for the axial coupling movement 
of the actuating rods, in each case an additional adjusting cylinder is 
provided at the rear end of the machine-tool spindle, so that altogether 
three such axial piston cylinders must be used, the tubular actuating rods 
of which must collectively be disposed in the hollow machine-tool spindle. 
If there is a disruption in the pressure medium system, the danger exists 
that the clamping device will come loose from the spindle flange, so that 
despite a high structural expense, an only inadequate operational 
reliability is provided. A very similar construction, which has the same 
drawbacks, is disclosed in German Offenlegungsschrift 30 45 537. 
Finally, German Offenlegungsschrift 34 10 670 discloses a further 
construction where a clamping device body, which is again provided with a 
flange ring, is fixedly connected via a self-centering radial tooth 
construction with an intermediate ring that is secured to the machine-tool 
spindle. The securing of the flange ring on the intermediate ring is 
effected via a plurality of clamping segments that couple a collar of the 
intermediate ring in a clamp-like manner with a connecting sleeve, which 
in turn is connected with the piston rod of one of the axial piston 
cylinders. An appropriate coupling between segments is effected between 
the front end of the securing rod and the drive member of the respectively 
mounted clamping device. In addition to a high expense for construction 
and the impossibility of providing a continuous bore for the supply of 
rod-like workpieces, this heretofore known construction has the drawback 
that both interlocking operations are a function of the position of the 
respective piston, so that if problems occur in the pressure medium 
system, not only a loosening but even a detachment of connections can 
occur. 
Starting with the previously described arrangement of German Patent 33 28 
291, it is an object of the present invention to embody such a mounting 
arrangement in such a way that via a straightforward construction and with 
small overall size, a reliable coupling is effected not only between the 
body of the clamping device and the spindle flange but also between the 
drive member and the securing rod, with this being accomplished without 
the need for an additional actuating cylinder at the rear end of the 
machine-tool spindle, whereby the possibility should be provided for being 
able to supply rod-like workpieces to a mounted clamping device through 
the machine-tool spindle.

SUMMARY OF THE INVENTION 
The mounting arrangement of the present invention is characterized 
primarily in that: the securing pins are secured to the clamping device 
and are axially oriented, i.e. are parallel to the orientation of the 
securing rod, with each securing pin being provided with notch means that 
has draw-in or tightening surface means; key rods, the number of which 
corresponds to the number of securing pins, are displaceably guided in the 
intermediate ring, with each key rod being provided with a wedge or key 
that is introducible in a respective one of the notch means of the 
securing pins; and a bayonet ring is rotatably yet axially non-shiftably 
mounted on a front end of the securing rod, and is adapted to cooperate 
with a bayonet flange formed on the drive member of the clamping device to 
effect the coupling of the securing rod to the drive member, with the 
bayonet ring being provided with an external tooth construction, and with 
at least one of the key rods being provided with a tooth construction that 
meshes with the tooth construction of the bayonet ring. 
The inventive construction has the advantage that no additional pressure 
medium cylinder is required on the rear end of the machine-tool spindle 
for mounting the clamping device body on the flange of the machine-tool 
spindle, and for coupling the clamping device drive member with the 
securing rod that is disposed in the hollow machine-tool spindle. Whereas 
the rotational movement of the inventive bayonet ring, which rotational 
movement effects the coupling between the drive member and the securing 
rod, is derived from the longitudinal displacement of at least one of the 
key rods, the longitudinal displacement of the key rods, which could be 
interconnected via the bayonet ring, is effected either by a spindle drive 
mechanism or by a pressure medium actuation. Both drive mechanisms are 
disposed in the intermediate ring that is secured to the spindle flange, 
so that where a pressure medium actuation is provided, it is merely 
necessary to provide appropriate pressure medium supply lines in the 
machine-tool spindle. Since for the inventive construction it is therefore 
necessary to provide only a single axial piston cylinder at the rear end 
of the machine-tool spindle, it is possible to embody the securing rod as 
a take-up tube having a central passage for the supply of rod-like 
workpieces to the clamping device. The axial orientation of the securing 
pins avoids a large bulky construction that extends out relatively far in 
a radial direction, so that the inventive construction is lightweight and 
hence has a low flywheel mass. 
Although the possibility exists for disposing the inventive key rods in the 
intermediate ring in such a way that they are displaceable in a radial 
direction, it is proposed pursuant to a further feature of the present 
invention to guide the key rods in the intermediate ring in such a way 
that they are displaceable in an approximately tangential direction, so 
that on the whole the intermediate ring has a small size and in particular 
has a smaller outer diameter. 
Pursuant to a further feature of the present invention, at least one of the 
key rods is adapted to be driven by a spindle drive mechanism that can 
preferably be actuated by a power drive that can be provided on the 
intermediate ring. Pursuant to an alternative embodiment of the present 
invention, at least one of the key rods is provided with at least one 
piston surface for a pressure medium drive mechanism. This pressure medium 
drive mechanism can operate, for example, against a built-in tensioning 
spring in a detachment direction, so that after the supply of pressure 
medium has been discontinued, the clamping position is assured by spring 
force. It is, of course, also possible to connect a double-acting piston 
with the key rod, so that in both directions of displacement the key rod 
can be shifted by pressure medium. In the event that all of the key rods 
mesh via teeth in the external thread of the bayonet ring, so that the key 
rods are interconnected with one another via the bayonet ring, it is 
sufficient that only one key rod be driven, either by a spindle drive 
mechanism or by a pressure medium drive mechanism. 
In the most straightforward design, the securing pins are secured to the 
body of the clamping device. However, pursuant to one preferred embodiment 
of the present invention, the securing pins can also be secured on a 
support ring that in turn is disposed on the rear end face of the 
respective clamping device. In this way, it is possible to equip 
conventional clamping devices with the securing pins, so that they can be 
used for an automatic rapid exchange. In order to increase the reliability 
of such a rapid exchange process, it is finally proposed pursuant to the 
present invention to provide the bayonet ring and the bayonet flange with 
inclined centering surfaces that cooperate with one another when the 
respective clamping device is mounted on the intermediate ring. 
Pursuant to an alternative embodiment, the notch that is provided with the 
tightening surface can be embodied as an annular groove. In such a case, 
the securing pins can be introduced into a keyhole-like opening in the key 
rod, the edge of which is embodied as a wedge surface for the tightening 
surface of the securing pin. 
In summary, the present invention provides an arrangement for mounting a 
power-operated clamping device on the front end of a hollow machine-tool 
spindle, with this being accomplished at a low cost for construction, 
while the resulting arrangement has a high operational reliability in a 
lightweight construction that provides the possibility for a central 
supply of rod-like workpieces, all without the need for having to use an 
additional pressure medium cylinder at the rear end of the spindle. 
Examples of clamping devices that can hold not only workpieces but also 
tools, include, in particular, chucks, mandrels, collets, gripping plates, 
or similar clamping devices for workpieces or tools. 
Further specific features of the present invention will be described in 
detail subsequently. 
DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, the longitudinal cross-sectional 
views of FIGS. 1 to 3 show the front end of a hollow machine-tool arbor or 
spindle 1 that is provided with a flange 1a; the spindle 1 is part of a 
machine tool, the remainder of which is not illustrated. A power operated 
clamping device 2 is secured to the flange 1a in such a way that it can be 
automatically exchanged for a different clamping device 2 within a very 
short period of time. The clamping device 2 illustrated in FIGS. 1 to 3 is 
embodied as a known multi-jaw chuck. In the drawings, a single clamping 
jaw 2a is shown that, just as the other, non-illustrated clamping jaws, is 
radially displaceably guided in the body 2b of the clamping device 2, and 
is actuated by a drive member 2c that in a known manner, which is not 
shown in the drawing, cooperates with all of the clamping jaws 2a and is 
moved in an axial direction by a spreader or securing rod 3. 
The rod 3 is disposed in the hollow machine-tool spindle 1, and is in turn 
actuated by a non-illustrated axial piston cylinder that is secured to the 
other end of the spindle 1. In the illustrated embodiment, the spreader or 
securing rod 3 is embodied as a tube having a central passage for the 
supply of rod-like workpieces to the clamping device 2. The central bore 
of the body 2b of the clamping device 2 is lined with a sleeve or bushing 
2d and is provided at the front end with a cover ring 2e. 
A support ring 4 is secured to the back side of the body 2b of the clamping 
device 2 via screws 4a. Secured to the back side of the support ring 4, 
using a spacer 5a and a screw 5b, is an axially oriented securing bolt or 
pin 5. Each of the securing pins 5 (a total of three pins are provided in 
the illustrated embodiment) is provided on its radially inwardly disposed 
surface with a notch 5c that forms a radially directed draw-in or 
tightening surface 5d. This can best be seen in FIG. 1. 
Secured at the forward flange 1a of the machine-tool spindle 1, via screws 
1b, is an intermediate ring 6 that is provided with receiving bores 6a for 
the securing pins 5. Projecting into each of these receiving bores 6a is a 
wedge or key 7a that is formed on a rod 7; the angled draw-in or 
tightening surfaces 7b of the keys 7a cooperate with the tightening 
surface 5d of the respective securing pin 5. In the illustrated 
embodiments, the key rods 7 have a circular cross-sectional configuration 
and are displaceably guided in the intermediate ring 6 in an approximately 
tangential direction; this can be seen in particular in FIGS. 4 to 7. 
Four different embodiments for the drive mechanism of the key rods 7 are 
shown in the respective cross-sectional views of FIGS. 4 to 7, which are 
taken along the line IV--IV in FIG. 3. 
With the first embodiment of FIG. 4, each key rod 7, which can be shifted 
in a longitudinal direction yet is guided in a non-rotatable manner in the 
intermediate ring 6, is provided with a spindle drive mechanism 8. In this 
embodiment, the drive mechanism 8 includes a spindle rod 8a, the external 
thread of which meshes with an internal thread of the key rod 7, with the 
spindle rod 8a being rotatably yet axially nonshiftably mounted in the 
intermediate ring 6 via a support ring 8b. The support ring 8b is held by 
a support cover 8c through which extends the spindle head 8d, which is 
provided with a hexagonal recess. Thus, rotation of the spindle rod 8a via 
drive applied to the spindle head 8d effects a longitudinal movement of 
the key rod 7 within the intermediate ring 6. 
An alternative embodiment of the key rod drive mechanism is illustrated in 
FIG. 6. With this embodiment, each key rod 7 is provided with a hydraulic 
or pressurized drive mechanism 9 that in this embodiment is double acting, 
with both ends of each key rod 7 being embodied as a piston surface 9a. By 
acting upon one of the two piston surfaces 9a of each key rod 7, the 
latter can be shifted in the desired direction within the intermediate 
ring 6. To facilitate illustration, the pressure medium lines or bores 
that are needed for supplying the pressure medium have not been 
illustrated. FIG. 6 shows merely that in the intermediate ring 6, each 
cylinder bore 6b, which receives a respective key rod 7, is closed off by 
a sealing cover 9b. 
In order during pressure loss to be able to hold the key rods 7 in the 
arresting or interlocking position, in the embodiment of FIG. 6 
compression springs 12 are provided that hold the key rods 7 in the 
arresting position, and the spring force of which must be overcome if the 
key rods 7 are to be transferred into the release position. 
Since not only the bodies 2b of the respective clamping device 2 must be 
connected with the flange 1a of the machine-tool spindle 1, but also a 
connection must be established between the drive member 2c of the 
respective clamping device 2 and the securing rod 3, the drive member 2c 
of each clamping device 2 is provided with a coupling piece 10 that is 
secured to the drive member 2c via screws 10a. The free end of this 
coupling piece 10 is provided with a bayonet flange 10b that in turn is 
provided with an inclined centering surface 10c (see FIG. 1). This bayonet 
flange 10b cooperates with a bayonet ring 11 that is similarly provided 
with an inclined centering surface 11a. The bayonet ring 11 and the 
bayonet flange 10b are provided with cams and recesses that extend in the 
radial direction, so that in a particular position these two parts 10b and 
11 can be pushed over one another in the axial direction, yet after 
rotation by the width of one cam or recess rest tightly against one 
another in the axial direction. In this manner, a coupling and uncoupling 
between the bayonet ring 11 and the bayonet flange 10b is possible. 
Whereas the coupling piece 10 that is provided with the bayonet flange 10b 
is non-rotatably secured on the drive member 2c, which is similarly 
nonrotatably guided in the body 2b of the clamping device 2, the bayonet 
ring 11 cannot be shifted axially yet is rotatably mounted on the front 
end of the securing rod 3, which for this purpose is provided with a tube 
flange 3a and a snap ring 3b (see FIG. 1). Rotation of the bayonet ring 11 
for the purpose of coupling or uncoupling is derived from the respective 
key rod drive mechanism, as can be best seen in FIGS. 4 to 7. 
FIG. 4 shows that one of the key rods 7, which is movable by a spindle 
drive mechanism 8, is provided with a rack-like tooth construction 7c that 
engages with a tooth construction 11b on the periphery of the bayonet ring 
11. Thus, shifting of the key rod 7 effects rotation of the bayonet ring 
11. By suitably coordinating the bayonet configuration and the tooth 
constructions 7c and 11b, a coupling between the bayonet ring 11 and the 
bayonet flange 10b is effected simultaneously with an interlocking or 
arresting of the securing pins 5 via the key rods 7. In the embodiment 
illustrated in FIG. 4, the two other key rods 7, instead of being provided 
with teeth 7c are provided with a recessed portion 7d, so that no 
connection between the three key rods 7 is effected via the bayonet ring 
11. 
The embodiment illustrated in FIG. 5 differs from that of FIG. 4 merely in 
that each of the key rods 7 is provided with a toothed construction 7c 
that meshes with the teeth 11b of the bayonet ring 11. In this way, a 
connection of the three key rods 7 is effected via the bayonet ring 11, so 
that it can be sufficient to activate merely the spindle drive mechanism 8 
of one of the key rods 7 in order to interlock the securing pins 5 and to 
couple the securing rod 3 with the drive member 2c. 
Also where a hydraulic or pressurized drive mechanism 9 is used for the key 
rods 7 as in the embodiment of FIG. 6, at least one of the key rods 7 is 
provided with a toothed construction 7c. In the embodiment of FIG. 6, the 
two other key rods 7 are again provided with recessed portions 7d. The 
embodiment illustrated in FIG. 7 again differs from that of FIG. 6 in that 
all three of the key rods 7 are respectively provided with teeth 7c, so 
that a connection of the three key rods 7 is effected via the bayonet ring 
11. 
In order to fix or mount a clamping device 2 on the intermediate ring 6 
that is secured to the flange 1a, the key rods are shifted via the 
respective drive mechanism 8 or 9 in such a way that the keys 7a are 
disposed beyond the receiving bores 6a for the securing pins 5. In so 
doing, the bayonet ring 11 is simultaneously rotated in such a way that 
the radially outwardly directed cams of the bayonet flange 10b can pass 
through corresponding recesses of the bayonet ring 11 during an axial 
mounting of the clamping device 2 on the intermediate ring 6. Via the 
inclined centering surfaces 10c and 11a that can be seen from FIG. 1, a 
guidance of the coupling piece 10 relative to the bayonet ring 11 is 
effected when the clamping device 2 has transferred from the starting 
position illustrated in FIG. 1 into the intermediate position illustrated 
in FIG. 2. At the same time, the securing pins 5 enter the receiving bores 
6a of the intermediate ring 6. During the further mounting movement of the 
clamping device 2, a final centering of the support ring 4 relative to the 
intermediate ring 6 is effected via central conical surfaces 4b and 6c 
that are provided on the support ring 4 and the intermediate ring 6 
respectively (see FIGS. 1 and 2). 
As soon as the clamping device 2 has attained the end position illustrated 
in FIG. 3, the key rods 7 are shifted with the aid of their spindle drive 
mechanism 8 or hydraulic or pressurized drive mechanism 9 in such a way 
that the angled tightening surfaces 7b of the keys 7a rest against the 
tightening surfaces 5d of the pertaining securing pins 5, which in this 
manner are positively held in position against the intermediate ring 6. At 
the same time that the key rods 7 are activated, a rotation of the bayonet 
ring 11 is effected, so that a coupling between this bayonet ring 11 and 
the bayonet flange 10b of the coupling piece 10, and hence a positive 
connection between the securing rod 3 and the drive member 2c of the 
clamping device 2, is effected. The clamping device 2 is then secured to 
the machine-tool spindle 1 and can be actuated by the securing rod 3 via 
the axial piston cylinder that is not illustrated in the drawings. 
The release and removal of the clamping device 2 is effected in the reverse 
order, whereby again the uncoupling movement for the release of the drive 
member 2c from the securing rod 3 is derived from the shifting movement of 
the key rods 7 that is necessary for releasing or disengaging the securing 
pins 5. 
The embodiment illustrated in FIGS. 8 and 9 shows a different type of 
arresting or interlocking for the securing pins 5, which are provided with 
a notch 5c in the form of an annular groove. The tightening surface 5d is 
formed on that annular surface that is closest to the free end of the 
securing pin 5. Securement of the securing pin 5 to the support ring 4 is 
effected by a nut 5e that is screwed onto a corresponding thread. 
Formed in each key rod 7 is a keyhole-like opening 13, through the greatest 
diameter portion of which the front end of the securing pin 5 can pass, 
and with the width of the elongated hole portion of the opening 13 
corresponding to the smaller diameter of the securing pin 5 in the region 
of the annular groove thereof. The edge of the key rod 7 in this region is 
embodied as a wedge surface 7e that cooperates with the tightening surface 
5d. 
When the securing pin 5 has entered the opening 13 and the key rod 7 is 
shifted, the wedge surface 7e, via the tightening surface 5d, pulls the 
securing pin 5 into the arresting position. Also in this case, the key rod 
7 is provided with a tooth construction 7c in order to drive the bayonet 
ring 11. 
The present invention is, of course, in no way restricted to the specific 
disclosure of the specification and drawings, but also encompasses any 
modifications within the scope of the appended claims.