System for exchanging cutting tools

A system for exchanging a cutting tool of a tool holder which includes a tool having a tool head which carries a cutting element and is provided with a bore. The tool head is removably connected to the tool holder. A spreading cylinder is provided for engaging the bore of the tool head to remove the tool head from the tool holder. The system further includes a magazine having a plurality of locations for receiving tool heads equipped with cutting tools.

BACKGROUND OF THE INVENTION 
The present invention relates to a system for exchanging the cutting tool 
of a work tool holder and in particular for exchanging cutting tools used 
for exterior and interior lathe work on machine tools. 
German Offenlegungsschrift (Application Published Without Examination) No. 
3,007,440 assigned to the assignee of the present application, discloses a 
tool for performing cutting work on the interior and exterior of metallic 
workpieces which includes a tool holder, a tool head and a cutting element 
wherein the tool holder and the tool head are connected together by means 
of a plurality of clamping pins which are locked and released by a 
clamping bolt movable within a cylindrical fitting. The clamping bolt can 
be moved manually or by machine. Tools of this type utilize different 
types of cutting elements, in particular, drills and reversible cutting 
plates, which are each mounted on a tool head. Tool heads are exchanged by 
the tool head being released by the machine, the tool head removed by 
means of an automatically controlled gripper and replaced by a different 
tool head having a further cutting tool. 
This tool arrangement however has the drawback that its use is restricted 
to tools where the tool heads are large compared to the tool bit itself 
since it is extremely difficult to exchange tool heads which are small 
compared to the tool bit by means of an automatically controlled gripper 
with the required degree of reliability and reproduceability. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a tool 
arrangement for working metallic and nonmetallic workpieces which includes 
tool heads (supports) whose size exceeds only slightly the size of the 
tool bits and in which can reliably be exchanged and accurately positioned 
in automatic operation. 
This is accomplished by the provision of a system which includes a 
magazine, a movable spreading cylinder, a tool holder having a clamping 
means mounted in a first recess, a tool head mounted in a second recess of 
the tool holder by means of the clamping element, and the tool head being 
provided with a bore intended to receive the spreading cylinder. A cutting 
element is fastened in a recess in the tool head by means of a clamping 
member. The magazine has several locations where tool heads, each equipped 
with a cutting element, can be accommodated. The system according to the 
invention permits reliable and very quick automatic exchange of cutting 
tools as well as the use of different cutting tools for different jobs. 
Due to the fact that the tool heads according to the invention are 
particularly small compared to the prior art tool heads, they can be 
accommodated on drilling rods for interior lathe work as well as on larger 
sized tool holders for exterior lathe work so that the system according to 
the invention becomes very versatile. By using particularly small tool 
heads, the entire tool is given optimal rigidity which positively 
influences the efficiency of the machine tool and considerably reduces the 
price of the system. The use of a spreading cylinder for the exchange of 
tool heads according to the invention makes possible a significant and 
unexpected reduction in the size of the tool head. 
In accordance with a further feature of the invention, an abutment plate is 
disposed in the recess of the tool head and an abutment piece is disposed 
in the second recess of the tool holder, on which the cutting element and 
the tool head, respectively, are supported. The abutment plate and the 
abutment piece can easily be exchanged when they are worn or damaged and 
thus impart almost unlimited service life to the tool holder and to the 
tool head. 
According to the invention, it is further provided that the clamping 
element for fastening the tool head in the tool holder engages the tool 
head in the bore intended to receive the spreading cylinder. This dual 
function of the bore, namely, receiving the spreading cylinder for the 
tool exchange of tool heads and receiving the clamping element for 
fastening the tool head to the tool holder permits a further reduction in 
the size of the tool head. 
The system according to the invention operates as follows. A plurality of 
tool heads are equipped with different types of cutting elements and are 
placed into pre-selected locations in the magazine. The movable spreading 
cylinder is automatically inserted into the bore of one tool head and 
moves the tool head from the magazine into the tool holder mounted in a 
machine tool. The tool head is firmly connected with the tool holder by 
means of a clamping element actuated by an automatically controlled 
clamping tool. After completion of the work, the connection between the 
tool head and the tool holder is released by the clamping tool, the 
movable spreading cylinder engages into the bore of the tool head and the 
tool head is returned to the magazine. Then the tool holder can be 
equipped with a further tool head. The various cutting elements are 
mounted on their respective tool heads such that when the tool heads are 
inserted in the tool holder and the tool holder positioned in the machine 
tool, the cutting points of the cutting elements are positioned at a 
common reference point. 
The spreading cylinder may be of the generally known type that has a 
cluster of fingers which, after their introduction into a bore of an 
article to be grasped and transported, are radially expanded to 
frictionally engage and thus clamp against the bore wall. The radially 
outward expansion and the radially inward retraction of the fingers may be 
effected by conventional mechanical and/or hydraulic means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The tool holder 1, shown in side perspective view at the lower portion of 
FIG. 1 and which may be a drilling rod or a head for reversible cutting 
plates, has a shaft 1a for mounting in a machine tool. In a recess 4 of 
the tool holder 1 there is disposed a flat tool head 6 which has a bore 7 
for engagement with a spreading cylinder 2. Tool head 6 which has a bottom 
face 6' and, parallel thereto, a top face 6" is firmly seated against a 
support surface 4' of the recess 4 of the tool holder 1 by means of a bell 
crank clamping element 5 (FIG. 3) or a straight, two-arm clamping element 
5' (FIG. 2). As a further alternative, the clamping element may be an 
eccentric bolt (not shown). The bore 7 whose axis is oriented 
perpendicularly to the bottom and top face 6', 6", may extend through tool 
head 6 into tool holder 1 to also accommodate the clamping element 5 or 5' 
as shown in FIGS. 3 and 2, respectively. The clamping element 5 or 5' is 
tightended or released by means of an automatically actuated clamping tool 
and such tightening may be effected via pressure piece 16. In FIG. 2, the 
clamping element 5 is secured in bore 7 by a plug 15 which seals the lower 
portion of the bore 7. 
As shown in FIGS. 1, 2 and 3, the cutting element 10 is fastened by the 
clamping member 9 in a recess 8 of the tool head 6. Recess 8 is in the 
form of a cut-out portion, the bottom (support surface) and side wall of 
which are designated 8', 8" respectively. The support surface 8' extends 
parallel to the bottom and top faces 6' and 6" of the tool head 6. The 
installation and exchange of the cutting elements 10 is effected manually 
and clamping member 9 may be a screw or a clamp. 
Reversible cutting plates of different shapes as well as tools for drilling 
and thread cutting may be used as cutting elements 10. The cutting 
elements 10 are preferably made of a hard metal composed of a binder metal 
and one or a plurality of hard metal carbides. 
As shown in FIG. 2, in order to protect the tool holder 1 against premature 
wear, the abutment piece 13 may be disposed in the recess 4 so as to 
support the tool head 6. The abutment piece 13 may be exchanged if worn 
out thus extending the service life of the tool holder 1. 
FIGS. 4a through 4c show for example the abutment piece 13 can 
advantageously be adapted to different shapes of the cutting elements so 
that optimum support of the tool heads 6 and of the cutting elements 10 
occurs during use of the tool. 
As shown in FIG. 2, wear on the tool head 6 can be reduced by use of an 
abutment plate 12 mounted in the recess 8 so as to support the cutting 
element 10. As in the case of abutment piece 13, abutment plate 12 can be 
exchanged when worn. 
The magazine 3, shown schematically in the center of FIG. 1, has several 
locations 11 for receiving in a side-by-side arrangement, tool heads 6 
equipped with different cutting elements 10. The magazine 3 is coded in a 
certain manner and can be rectangular or circular in shape. The spreading 
cylinder 2 can be moved in any direction to displace the tool heads 6 with 
the various cutting elements 10. The spreading cylinder 2 is controlled 
automatically and is actuated pneumatically or hydraulically. 
The operation of the apparatus is illustrated in FIG. 1. As shown in FIG. 
5, during operation of the apparatus according to the invention, the 
differently shaped cutting elements 10 disposed on the tool head 6 can be 
positioned in the cutting area in such a manner that all their cutting 
points are oriented toward the setting point 14. The setting point 14 is 
the reference point for programming the apparatus according to the 
invention, however, as also shown in FIG. 5, because of the various 
shapes, the reversible cutting plates are able to cover an operating range 
of 280.degree. in the cutting area. 
It will be understood that the above description of the present invention 
is susceptible to various modifications, changes and adaptations and the 
same are intended to be comprehended within the meaning and range of 
equivalents of the appended claims.