Coupling adapter

A coupling adapter (1) for positioning a tool (90) in a particular given position with high repetitive precision on a chuck (80) that can be activated by a medium for a machine tool. The chuck (80) is equipped with elements (52, 54, 82, 55, 57, 58) of a first holding system and the tool (90) with elements of a second holding system, with a pressure-medium source that is controlled by a central control device and connected to the chuck (80) through a first medium channel (81) provided in the machine tool. The coupling adapter (1) is provided on a first end face with counter-elements (52, 54, 55, 56, 57, 58) of the first holding system and on a second end face (29) with counter-elements of the second holding system and has a device on the chuck (80) for clamping depending on the medium pressure and a holding device for the tool (90). The holding device for the tool (60, 75, 76) is connected to the pressure-medium source through a second medium channel (72, 85), which extends through the coupling adapter (1) and the chuck (80).

The invention concerns a coupling adapter for positioning a tool in a 
particular given position with high repetitive precision on a chuck that 
can be activated by a medium for a machine tool, whereby the chuck is 
equipped with elements of a first holding system and the tool with 
elements of a second holding system, with a pressure-medium source that is 
controlled by a central control device and connected to the chuck through 
a first medium channel provided in the machine tool. The coupling adapter 
is provided, on a first end face, with counter-elements of the first 
holding system and on a second end face with counter-elements of the 
second holding system and has a clamping device on the chuck depending on 
the medium pressure and a holding device for the tool, whereby the holding 
device for the tool is connected to the pressure-medium source through a 
second medium channel, which extends through the coupling adapter and the 
chuck. 
Various holding systems are known, which are described in detail in 
documents DE 26 46 951 C3 and EP 255,042 B1 (U.S. Pat. No. 4,855,558), 
incorporated by reference herein. With a holding system of this type, a 
work-piece to be processed can be coupled or held, possibly by means of a 
work-piece carrier, to the chuck of a machine tool, especially an 
electrical-discharge machine, with extraordinarily high precision. Since 
the work-piece, for example an electrode, can be used as a tool after it 
has been processed, the concept of tool used to described the present 
invention also covers the work-piece. 
Selection of the holding system to be used in each case depends on, among 
other things, the type of processing or even on the weight of the tools. 
On the other hand, the machine tool is provided with a pre-determined 
holding or coupling system, so that a desire arises for a transition piece 
called an adapter, which permits the transition from the holding system on 
the machine side to the holding system adjusted to the work-piece without 
loss of precision in positioning. The operation of modern machine tools is 
controlled numerically by means of a central control device that makes 
automatic attachment and release of an adapter to the chuck of the tool 
machine possible by means of a tension bolt. The tension bolt can have on 
the side a profile adapted to the gripper of an automatic exchange device, 
by means of which the tension bolt can be manipulated. 
The invention is therefore based on simplifying the task of providing the 
coupling adapter mentioned above. For this, according to the invention, it 
is provided that the holding device is connected to the pressure-medium 
source through a second medium channel, which extends through the coupling 
adapter and the chuck. The coupling adapter according to the invention 
thereby becomes accessible to numerical control by the central control 
unit, so that attachment of a tool to the coupling adapter coupled to the 
chuck, and also its release, can be accomplished automatically. The 
invention expands the possibilities for controlling the machine tool by 
referring to a second reference plane, which differs from the reference 
plane used up to now only by a constant that is determined by the 
pre-determined measurement of the adapter in the z-direction. 
In a preferred embodiment of the invention, it is recommended that the 
transition from the second medium channel of the coupling adapter to the 
chuck be fed through an element/counter-element pair of the first holding 
system. This element/counter-element pair can be any pair that positions 
the coupling adapter unambiguously with respect to the chuck in the axial 
direction (z-direction). If, in a further development of the invention, 
the tool is coupled to a tension anchor that can be inserted into the tool 
holding device, it is recommended that the second medium channel open into 
a pressure chamber of the coupling adapter, in which an elastically 
applied piston can be moved, whereby the piston controls the radial 
meshing of arresting elements, for example balls, in radial recesses in 
the tension anchor. 
In another preferred embodiment of the invention, it is provided that an 
external contour, the size of which is conveniently equal to that of the 
profile of the tension bolt, is formed on the tool that can be coupled to 
the tension anchor. With this, the tool becomes capable of being 
manipulated by grippers, advantageously, in particular, by grippers with 
the same geometry. 
To the extent that the first and/or the second holding system has/have 
spring elements, another development of the invention, of the type where 
these spring elements are formed on the upper side and/or the lower side 
of the coupling adapter is recommended. 
Other advantageous embodiments of the objects of the invention are within 
the scope of the claims and sub-claims.

The coupling adapter designated as a whole by 1 has a lower casing part 2, 
with essentially the shape of a pot, the top opening of which is closed by 
a lid 3 that is screwed on, with the exception of a central channel 32 in 
the lid 3. On the free upper side of the lid 3 an extension 4 is screwed 
on by means of several screws 41, 42, 43, 44. The square-shaped extension 
4 has on its upper side four radially arranged grooves 45, 46, 47, 48, 
which open into a stepped circular central passage hole 51 drilled in the 
extension 4. Between every pair of grooves 45, 47, 46, 48, four angled 
surface segments 57, 56, 58, 55, ground flat and lying in a plane, are 
defined, which serve together as z-reference surfaces. Each of the grooves 
has, at its transition to the next surface segment, opposing lips formed 
by back-cuts as elements of a first holding system, which are denoted by 
52 and 54 at groove 46. The first holding system is formed in the manner 
described in detail in document EP 255,042 B1 (U.S. Pat. No. 4,855,558), 
mentioned above. Correspondingly, the chuck, shown only schematically in 
FIG. 3 and denoted by 80, has strips protruding from its lower side, which 
are arranged to fit into the grooves 45, 46, 47, 48 cross-wise, and when, 
for example, the strips 82 penetrate between the axially elastic lips 52, 
54 as the coupling adapter 1 is attached to the chuck 80, they thereby 
position the coupling adapter 1 unambiguously in the x- and y-directions, 
perpendicular to the vertical z-direction. In addition, on the lower side 
of the chuck 80, there are four tabs (or posts), each of which sits on one 
of the surface segments 55, 56, 57, 58 to define the spanning or holding 
path in the z-direction as a z-reference, as is shown in FIG. 3 for tabs 
84 and 86 with reference to surface segment 56, 58. 
In a manner known from the above-mentioned European document, a tension 
bolt 7 is inserted into the passage hole 51 in the extension 4, which bolt 
is placed in a corresponding recess in the chuck 80 and can be pulled in 
by means of compressed air to attach the coupling adapter 1 to the chuck 
80. 
From the lower side of the lid 3, which lies at its edge on the lower part 
2 of the casing an extension 31 in the shape of a single tube extends to 
the middle, which has a stepped hole 39 aligned with the central channel 
32, and extends through the interior of the casing 2 as far as a central 
opening 23 in the lower end segment 21 of the casing part 2. The interior 
space enclosed by the wall 22 of the casing part 2 and the extension 31 
thus forms a ring-shaped cylinder chamber 24, in which a piston 60 can be 
moved axially. The piston 60 is sealed by ring seals 61 or 62 against a 
cylindrical segment of the inner surface of the wall 22 or the opposite 
outer wall of the extension 31; between the upper side of the piston 60 
and the lower side of the lid 3 there remains a chamber 25, into which a 
pressure-medium channel, or a second medium channel, opens. The 
pressure-medium channel 72 passes through the lid 3 and the extension 4 
and opens onto the upper surface segment 57 at a point at which the tabs 
of the chuck 80 come to placed when the coupling adapter 1 is attached. As 
is known from document EP 255,042 B1, a pressure-medium channel, connected 
to a pressure-medium source, not shown, penetrates through each of the 
tabs. Release of the pressure medium from the pressure-medium source is 
shown in FIG. 3 by the arrow 85. It is in contact with the pressure-medium 
channel 72 when the coupling adapter 1 is thus attached to the chuck 80. 
If a pressure medium, for example compressed air, is fed into the 
pressure-medium channel 72, the piston 60 can yield to the pressure that 
has built up in the chamber 25 against the effect of a spring 26 that is 
braced on the inner side 27 of the wall 22, in a downward direction, 
specifically at most until the lower side 63 of the piston 60 comes to 
rest on an inner level 28 of the wall 22. When the piston 60 is resting on 
the level 28, a ring-shaped recess 64 in the piston 60 comes to radial 
openings 34, 35 in the extension 31, in which openings balls 36, 37 can 
move radially as arresting elements. The balls 34, 37 can then yield in 
the radial direction in the recess 64 and release the path directed 
outward of a tension anchor 75 down from the hole 39 and the opening 23. 
If pressure is released from the pressure-medium channel 72, the piston 60 
travels upward due to the action of the spring 26, so that the balls 36, 
37 are pushed radially inward by the piston 60 in the openings 34, 35, and 
they protrude in the hole 39 in such a way that they can support a collar 
76 on the tension anchor 75. Therefore, when an impulse of compressed air 
is applied through the medium channel 72 to the chamber 25, the tension 
anchor 75 can be pulled away, downward from the coupling adapter 1, for 
example by an automatic gripper. On the other side, the tension anchor 75 
is held in the coupling adapter 1 by the pressure spring 26 when there is 
no pressure in the chamber 25. It will be understood that giving a 
compressed-air impulse to the chamber 25 can be controlled by the central 
control of the machine tool, not shown, to the spindle sleeves of which 
the chuck is attached in this way. Moreover, in a practical 
implementation, several pressure springs 26 can be provided in the 
circumferential direction. 
The tension anchor 75 carries a tool 90, of which the part of the upper 
surface next to the tension bolt 75 is provided with elements of a second 
holding system. Correspondingly, at the free end 29 of the coupling 
adapter 1, counter-elements of the second holding system are formed, which 
work together or cooperate with the elements on the tool 90 when the 
tension bolt 75 is attached. This second holding system can be either the 
one described in document DE 26 46 951 C3, or else be shaped in the way 
shown in FIG. 4. At the free end 29, three spring blades 71, 73, 75, 
equally spaced in the circumferential direction, are formed by 
corresponding cuts, which are elastic in the direction of the axis 2. Each 
of the spring blades 71, 73, 75 ends at a given distance before a fixed 
stop 74, 76, 77, where the stops 74, 76, 77 are likewise spaced equally in 
the circumferential direction. Thus between each spring blade 74, 76, 77 
and its associated opposite stop 74, 76, 77 there remains a gap, into 
which one each of three cone-shaped radial tongues 95, 97, 99, equally 
spaced in the circumferential direction, of the tool 90 can penetrate. The 
tongues 95, 97, 99 have a ridge width when viewed in the circumferential 
direction that is smaller that the width of the gap mentioned between each 
pair of spring blade and stop and a base width that is larger than the 
width of the gap mentioned. Therefore, if the tool 90 is attached to the 
coupling adapter (1) in the manner described by means of the tension 
anchor 75, which is anchored in a manner not shown in a central hole 70 of 
the work-piece 90, each of the tongues 95, 97, 99 presses into the gap 
between one of the spring blades 71, 73, 75 and the corresponding opposite 
stop 74, 76, 77. The penetration depth in the direction of the axis 92 is 
limited by the fact that the stop surfaces 87, 88, 89 formed on the upper 
side of the tool 90, which lie in a plane, come to rest on the free end 
surface 29. As shown, the stop surfaces 87, 88, 89 are at equal distances 
in the circumferential direction, and between every two neighboring 
tongues 95, 97, 99 a stop surface 87, 88, 89 is formed on the work-piece 
90. 
It can be seen from FIG. 1 that the tension anchor 75 can be inserted into 
the coupling adapter 1 in alignment with the middle axis 92 of the latter 
and that it is therefore likewise in alignment with the tension bolt 7. 
The free end surface 29 lying perpendicular to the middle line 92 forms a 
z-reference for attachment of the work-piece 90. Through the end section 
21, a compressed-air channel 33 is drilled, which communicates with the 
chamber 24. Another compressed-air channel 30 opens into the chamber 24, 
which channel is made through the upper part of the wall 22 and continues 
in a compressed-air channel 74 in the lid 3. At the end of compressed-air 
channel 74, a nipple 78 is screwed on, which communicates with a 
counter-piece 79 on the chuck 80 when the coupling adapter 1 is attached 
to the chuck 80. From the counter-piece 79, a compressed-air channel 
extends through the chuck 80 to the connection at the compressed-air 
source at arrow 83. As arrow 83 indicates, the compressed-air channel 74 
is then supplied with compressed air under control of the central control 
unit when the tension anchor 75 is attached to the work-piece 90 against 
the coupling adapter 1 in the manner described. The compressed air that 
consequently flows out of the coupling adapter 1 through the chamber 24 
and the compressed-air channel 33 cleans the counter-reference surface 
with respect to the reference surface 29 at the time of the attachment. 
Arrow 81 shows the connection of the pressure-medium source to a 
compressed-air channel in the interior of the chuck 80, which is applied 
to release the coupling of the coupling adapter 1 to the chuck 80 and is 
called the first medium channel. 
The tension bolt 7 has, like the tension bolt known from EP 255,042 B1, a 
section 91 which remains free after the tension bolt 7 is coupled to the 
coupling adapter 1 and the tension bolt 7 is inserted into the chuck 
between the chuck 80 and the upper side of the extension 4. At section 91, 
a profile 93 is formed, which is intended to work together with a 
counter-profile at the gripper of a manipulator, not shown, for example an 
automatic tool replacer. In the embodiment example shown, the profile 93 
has two shoulders extending radially inward, opposite each other with 
respect to the middle line 92, which can support the gripper. 
The tool 90, the upper side of which, located radially outside the tension 
anchor 75, is provided with the elements mentioned of the second holding 
system, has an outer contour 94 on the upper side lying opposite the 
coupling adapter 1, which contour consists, for example, of two shoulders 
96 extending radially inward, symmetric with respect to the axis 92. The 
sizes and also the geometric shape of the profile 93 are the same as those 
of the outer contour 94. Therefore, the gripper mentioned can also grip 
the work-piece 90 on its outer contour 94 according to an offset 
corresponding to the extension of the coupling adapter 1 in the 
z-direction, and, after the chamber 25 is supplied with compressed air 
through the pressure-medium channel 72, pull the tension anchor 75 out of 
the hole 39. The offset mentioned is a constant machine parameter, which 
can be stored in the control unit, not shown. The control device can 
therefore either release the tension bolt 7 or the tension anchor 75 with 
the workpiece 90, in correspondence with the given control program, from 
the machine tool or attach it to the machine tool.