GB1566823A

GB1566823A - Machine tool with automatic tool exchanger

Info

Publication number: GB1566823A
Application number: GB1761577A
Authority: GB
Original assignee: Toyoda Koki KK
Current assignee: Toyoda Koki KK
Priority date: 1977-04-27
Filing date: 1977-04-27
Publication date: 1980-05-08

Description

(54) MACHINE TOOL WITH AUTOMATIC TOOL EXCHANGER (71) We, TOYODA-KOKI KABUSHIKI KAISHA, a Japanese Company, of 1-1, Asahi- machi, Kariya-shi, Aichi-ken, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates generally to machine tools and, more particularly, to a machine tool with an automatic tool exchanger for exchanging a tool received in a tool spindle with another tool selected out of a tool magazine.

In a known machine tool of this kind, a drive key and a key-way complemental thereto are provided respectively on a tool spindle and each of the tools to transmit the driving force of the tool spindle to the tool received therein, and the tool spindle is arranged to be indexed to a predetermined angular position prior to a tool exchange operation. At tool holding portions of a tool magazine, there are provided detent members with which the key-ways of the tools are respectively snugly engaged, so as to prevent the tools from angularly moving even a little in the stored state. Furthermore, the drive key and the key-way are machined to almost the same width, such as, for example, the former being 25,4 mm. wide, the latter being 25.7 mm. wide, and thus, when engaged, to establish little clearance or play therebetween so as not to permit relative rotation between the tool spindle and the tool received by the same.

In the prior art machine tool, therefore, when the tool is presented to the tool spindle with its key-way not exactly aligned with the drive key, it is impossible to complete the automatic tool exchange operation since, in such an event, the drive key necessarily interferes with a flange portion of the tool. This trouble occurs, though rarely, due to the fact that there are many technical difficulties in holding all of the tools stored within the tool magazine at exactly the same angular position and also in presenting the tool to the tool spindle with its key-way exactly aligned with the drive key.

It is a primary object of the present invention to provide a machine tool with an improved tool exchanger having high reliability in operation.

According to the present invention, in one aspect, there is provided a machine tool as set forth in claim 1 of the appended claims.

According to the present invention, in another aspect, there is provided a machine tod as set forth in claim 11 of the appended claims.

According to the present invention, in yet another aspect, there is provided a machine too as set forth in claim 16 of the appended claims.

Other desirable features of the machine tool are set forth in the subordinate claims.

The present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like or corresponding parts throughout the several views, and wherein: Figure 1 is a schematic diagram illustrative of the basic tool exchange operation of the present invention; Figure 2 is a front elevation view of a machine tool constructed in accordance with the present invention Figure 3 is a longitudinal sectional view of part of the machine tool taken along the line III-III of FIGURE 2; Figure 4 is a cross-sectional view of part of the machine tool taken along the line IV-IV of Figure 3; Figure 5 shows a development diagram of the can drum shown in Figure 4; Figure 6 is a longitudinal sectional view of part of the machine tool taken along the line VI-VI of Figure 2, showing particularly one of the storage sockets mounted upon the tool magazine.

Figure 7 is a cross-sectional view of part of the machine tool taken along the line VII-VII of Figure 6; Figure 8 shows a portion of an electric control circuit employed to accomplish the tool exchange operation; Figure 9 shows a modification of the fine indexing device shown in Figure 4; and Figure 10 shows development diagram of the cam drum shown in Figure 9.

Referring now to the drawings, and more particularly to Figure 1 thereof, illustrative of the basic tool exchange operation of the invention, there is provided a tool spindle 10, from one end of which a drive key lOa protrudes to be engageable, with play, with a keyway 1 la cut out on a flange of a tool or a tool holder 11. In the state indicated by the solid line, clearances, each corresponding to an angle a; are established between the drive key 1 0a and both side walls of the key-way 1 la. and the tool spindle 10 and the tool 11 are thus relatively rotatable within an angular extent 2a, Generally, the tool or the tool holder 11 which is extensively used in this field has a tapered shank No. 50 taper, to British Standard 1660, Part 3, 1953, and the key-way Ila of the tool 11 is machined to be 25.7 mm wide.

The width of the drive-key lOa is made narrower, within the range of 5 to 70%, than that of the key-way 1 la. In this instance, the clearance between the drive key 1 0a and the key-way 1 la increases by an angle of 0.9 degrees each time the width of the drive key is reduced lmm. However, it should be noted that if the width of the drive key 1 0a is made narrower, within a range less than 5% of that of the key-way 1 la, the advantage resulting from such is scarcely obtained, and that if the width of the drive key 1 ova is made narrower, by more than 70% relative to that of the key-way 1 la, a problem may occur with the strength of the drive key lOu.

The tool 11 stored in a tool holding portion, which is in a tool removal station of a tool magazine 24, is removed therefrom and presented onto the tool spindle 10 by a tool exchange arm 13 which operates, in order, through an extension movement, a rotational movement of an angle of 180 degrees, and a withdrawal movement. A detent pin 14 protrudes at the tool holding portion of the tool magazine 24 and is engaged with the keyway 1 la of the tool 11 with a play of an angular extent 2a, within which the tool 11 is therefore rotatable. Although, in Figure 1, only one tool holding portion is shown, which has been indexed to the tool removal station, it will be understood that a detent pin 14 is provided at each of the several tool holding portions and in a similar angular relationship, that is, at the three o'clock position of each tool holding portion, as shown in Figure 1.

As the exchange arm 13 is such that it is rotated through an angle of 180 degrees, the tool spindle 10, prior to a tool transfer operation, is so stopped as to position the drive key lOa at a predetermined angular position corresponding to the detent pin 14 in the tool removal station, namely at the nine o'clock position, as shown in Figure 1, and in this condition, the tool transfer operation is performed.

Thus, even when the key-way 1 la of the tool 11 presented by the tool exchange arm 13 onto the tool spindle 10 is deviated within an angular extent of + a from the nine o'clock position, it is possible for the key-way 1 la of the tool 11 to be engaged with the drive key lOa, owing to the provision of the clearance 2a.

Accordingly, the problem of the tool exchange operation being interrupted because of nonengagement of the drive key 1 Oa with the keyway 1 la is avoided, whereby reliability in the exchange operation is enhanced. Moreover, the clearance a, which appears between rear surfaces of the drive key 1 0a and the key-way 1 la, is eliminated before a machining operation by rotating the tool spindle 10 and, therefore, there can also be realized a tool drive superior to those of known apparatus with respect to its reliability.

Referring to Figures 2 to 7, a preferred embodiment will now be described. A machine tool illustrated in Figure 2 has a column 20, on which a spindle head 21, rotatably supporting a tool spindle 10, is guided to be slidable in a vertical direction. On a work table 22, which is slidable in longitudinal and transverse directions relative to the column 20, there is indexably mounted a rotary table 23, onto which a workpiece W is attachable. A tool magazine 24 for storing a plurality of diverse tools 11 is indexably mounted on the top of the column 20.

Between the tool magazine 24 and the tool spindle 10, there is provided an automatic tool exchanger 15, having an exchange arm 13, which is provided with a pair of grippers 13a, 13b, at both ends thereof. Tools stored within the tool magazine 24 and received in the tool spindle 10 are gripped by the grippers 13a, 13b, removed therefrom, mutually replaced through the rotation of an angle of 180 degrees, and inserted thereinto and, in such a manner, a tool exchange operation is carried out.

As best shown in Figure 3, the tool spindle 10 is formed at one end thereof with a tapered bore 12 for receiving the tool 11 and is provided with a drive key 1 0a protruding from the end face. The tool 11, when inserted into the tapered bore 12, is firmly clamped upon the tool spindle 10 as a pull stud 16, protruding from its rear end, is drawn by a snap member 32, connected with one end of a drawing rod 31, which a set of washer springs 30 are always drawing in a rearward direction. In face to face relation with the rear end of the drawing rod 31, there is disposed an unclamping cylinder .33, a piston 34 of which, when advanced, compresses the washer springs 30, so as to advance the drawing rod 31 and to thereby release the pull stud 16 from the snap member 32, so that removal of the tool 11 becomes possible.

A gear member 35 is keyed on the tool spindle 10 substantially intermediate the length of the same. On the gear member 35, there are formed, in spaced relation, a large gear 35a and a small gear 35b, with both of which a shiftable gear member 36 is selectively engageable. The shiftable gear member 36 is held upon and spline-engaged with a spline shaft 38, which is in tam connected with an output shaft 37a of an electrical motor 37. A coupling 39 is provided with a disc 39a, to which a brake unit 40 is disposed to press its brake pads. A dog 42 is secured upon the forward end of the tool spindle 10 at a predetermined angular disposition. When electrical conduction to the motor 37 is stopped after a machining operation, but rotation of the tool spindle 10 still continues because of its inertia, a proximity switch PRS 1 secured upon the spindle head 21 is activated by the dog 42, to energize the brake unit 40, so that the tool spindle 10 can be stopped within a predetermined angular extent (course index).

At the rear end of the tool spindle 10, there is secured an index plate 41 having a protrusion 41a. After being positioned by the brake unit 40, the dog 42 and the proximity switch PRS 1, within such a predetermined angular extent 2c as to be engageable with a pair of index claws 43a, 43b, as shown in Figure 4, the protrusion 41a of the index plate 41 gets sandwiched between the index claws 43a, 43b, as they approach each other, and is thus indexed to a predetermined angular position.

This constitutes a fine indexing device generally indicated by the reference numeral 48, the detail of which will now be described. A pair of pilot bars 44, only one being shown, are fixed on the spindle head 21 to be extended tangentially in the index plate 41, and the index claws 43a, 43b are mounted on and slidable along the pilot bars 44. Follower pins 49a, 49b, embedded in the rear ends of the index claws 43a, 43b, are engaged, respectively, at spherical head portions thereof with two closed cam slots 45a, 45b formed on the circumferential surface of a cam drum 45, which is supported on the spindle head 21 to be rotated about its axis parallel with the bars 44. The cam drum 45 is drivingly connected at its one end with an index motor 46 mounted on the spindle head 21 so as to be rotated thereby in one direction, the motor 46 containing a speed reduction mechanism.

As shown in the development plan of Figure 5, at an angular position 81 the cam slots 45a, 45b are formed parallel along the upper and lower verges respectively of the cam drum 45 and, thus, the index claws 43a, 43b, guided thereby, are both maintained withdrawn from the rotational locus of the protrusion 41a to the most open condition, as indicated by the phantom lines in Figure 4, so as to permit the rotation of the tool spindle 10. When a limit switch LS1 is activated by a dog 47a, it is detected that the index claws 43a, 43b are at the angular position 81 of the cam drum 45. A first cam segment CS1 extends from the angular position 81 to another angular position 82', within the extent of which the cam slots 45a, 45b gradually approach each other to sandwich the protrusion 41a between the index claws 43a,43b, whereby the protrusion 41a, having been positioned within the angular range or extent 2P, is indexed to the three o'clock position, as shown in Figure 4. Another limit switch LS2 is provided to detect another angular position 82 of the cam drum 45, when activated by a dog 47b. Furthermore, a second cam segment CS2 is defined between the position 82' and another angular position 83, within the extent of which the cam slots 45a, 45b are inclined upwardly with a parallel relation to each other. Accordingly, within this extent, the index claws 43a, 43b are upwardly moved together with the protrusion 41a sandwiched thereby, which thus rotates the index plate 41 and the tool spindle 10 a little in a counter clockwise direction, as viewed in Figure 4. A third cam segment CS3 extends from the position 83 to the position 81, between which the cam slots 45a, 45b are gradually separated from each other so as to remove the index claws 43a, 43b from the rotational locus of the protrusion 41a.

An exchange arm 13, as shown in Figure 6, is fixed on one end of a hollow shaft 50 which is able to both rotate about its own axis and move in a straight axial line. Within a support housing 51 for operably supporting the hollow shaft 50, there are formed cylinders 54 and 56, the former of which slidably contains therein a piston rack 53 movable perpendicularly of the hollow shaft 50, and the latter of which slidably contains a piston 55 movable parallel to the hollow shaft 50. The piston rack 53 is meshed at its rack tooth portion 53a with a spur gear 50a cut upon the outer periphery of the hollow shaft 50 and is allowed to move in its axial direction in such meshed condition, thus causing rotation of the hollow shaft 50.

A piston rod 57 of the piston 55 is connected with a hydraulic distributor 58, which, at the rear end of the hollow shaft 50, is so arranged as to be rotatable relatively thereto, that is, to permit rotation of the hollow shaft 50 therewithin, but to move integrally therewith in the axial direction, and thus, the reciprocation movement of the piston 55 can cause the hollow shaft 50 to move forwardly and rearwardly therewith.

At both the ends of the exchange arm 13, a pair of grippers 13a, 13b are provided being pivotably supported about pivot pins 60, 61, on which pinions 62, 63 are keyed, which are in turn meshed through idle pinions 64, 65 with rack bars 66, 67 slidable radially of the hollow shaft 50, respectively, as best shown in Figure 7. The inner ends of the rack bars 66, 67 are pivotably connected, respectively, to one end of links 68, 69, of which the other ends are mutually overlapped and pivotably connected with one end of a floating link 70.

The other end of the floating link 70 is pivotably connected to a slider 71 inserted into the hollow shaft 50, and the slider 71 is further connected through a rod 74 to a piston 73 inserted into a gripping cylinder 72 which is formed at the rear end of the hollow shaft 50, within the hydraulic distributor 58. Therefore, when the piston 73 is forwardly moved, pushing the floating link 70 to radially extend the links 68, 69, the rack bars 66, 67 are moved away from each other, so that each pair of grippers 13a, 13b are closed to grip the tools 11. To the contrary, the rearward movement of the piston 73 causes the links 68, 69 to be folded, moving the rack bars 66, 67 toward each other and consequently, the grippers 13a, 13b are opened to release the tools 11.

From each of the tool holding portions of the tool magazine 24, as shown in Figures 2 and 7, there protrudes, at the three-o'clock position, a detent pin 14, by which the key-way 1 la of the stored tool 11 is prevented from deviating from the three o'clock position more than the angular extent + a. The aforementioned drive key 1 Oa has substantially the same width as those of the detent pins 14 in its rotational direction.

The operation of the machine tool constructed as above will now be described.

When a machining operation is completed, the spindle head 21 is moved upwardly to be positioned at the uppermost travelling end, as shown in Figure 2, and at the same time, the rotation of the tool spindle 10 is topped in the following manner. That is, as the motor 37 is first de-energized and then, the brake unit 40 is energized at the time when the proximity switch PRS1 detects that the tool spindle 10 reaches a predetermined angular position, the tool spindle 10 is stopped to place the protrusion 41a of the index plate 41 within the predetermined angular extent, as shown in Figure 4 (coarse index). Upon the completion of the coarse indexing operation, the index motor 46 is energized until the cam drum 45 is angularly moved from the position 81 to the position 82, whereby the index claws 43a, 43b are moved toward each other to be closed.

Accordingly, the protrusion 41a is angularly adjusted and positioned at the nine o'clock position accurately corresponding to the detent pin 14 (fine index).

The tool magazine 24 has beforehand been rotationally indexed to present a fresh tool 11, to be next used, to the tool removal station or tool exchange station. As soon as the fine indexing operation is completed, the grippers 13a, 13b of the exchange arm 13 are closed to simultaneously grip a previously used tool 11, received within the tool spindle 10, and the fresh tool 11 indexed to the exchange station.

The unclamp cylinder 33 provided at the rear end of the tool spindle 10, is operated to advance the piston 34, pushing the drawing rod 31 against the washer springs 30, so that the used tool 11 is unclamped. Following this, the exchange arm 13 is advanced by the forward movement of the piston 55, and accordingly of the hollow shaft 50, to remove the tools 11 from the tool spindle 10 and the tool holding portion, and subsequently, the piston rack 53 is operated to rotate the hollow shaft 50 and the exchange arm 13 therewith through an angle of 180 degrees. Accordingly, the tool 11 removed from the spindle 10 is aligned with the tool holding portion, and the tool 11 from the same with the spindle 10.

The rearward movement of the piston 55 is then effected to rearwardly move the hollow shaft 50 and to retract the exchange arm 13 therewith and, as a result, the used tool 11 and the fresh tool are inserted respecitvely into the tool holding portion and the tool spindle 10.

In this tool insertion, since the key-way 1 la of the fresh tool 11 is held within the angular extent i a with the nine o'clock position as the central figure, the tools 11, 11 are inserted respectively without interferring with the drive key 1 Oa of the tool spindle 10 and the detent pin 14 of the tool holding portion. In this event, between the drive key lOa and the key-way 1 la of the fresh tool 11, there appears a clearance which reaches 2a at its maximum, but nevertheless positive drive of the tool 11 by the drive key lOa is achieved in the following manner.

That is, when the tool insertion operation is completed, the index motor 46 is energized to rotate the cam drum 45 from the angular position 82 to 81 and thus, both The index claws 43a, 43b are upwardly moved by an amount Al, as indicated in Figure 5, on the way up to the angular position 83. Accordingly, the index plate 41, along with the tool spindle 10, is rotated a little in the counter-clockwise direction, so that no clearance is formed between the drive key lOa and one of the key-way walls drivingly urged thereby.

The piston 34 of the unclamping cylinder 33 is thereafter moved in the rearward direction to clamp the fresh tool 11 upon the tool spindle 10 by means of the force of the washer springs 30, and then, the grippers 13a, 13b are opened to release the tools 11, 11. The spindle head 21 is immediately moved toward the machining position and, at the same time, the spindle drive motor 37 is operated to rotate the tool spindle 10 in the counterclockwise direction.

Accordingly, another machining operation is initiated in such a condition that the fresh tool 11 is positively and certainly driven by the drive key lOu.

Figure 8 shows a portion of an electric control circuit employed to accomplish the above-described operation. When a normally open contact cr100 is closed, upon the completion of the coarse indexing operation, a magnetic relay CRl lO is energized and selfheld, since a normally open contact crM06 for instructing the tool exchange operation has already been closed. The energization of the relay CR110 operates the index motor 46 to rotate the cam drum 45. When a normally open contact ls2 of the limit switch LS2 is closed, a magnetic relay CR1 11 is energized and deenergizes the relay CRl l O by opening its normally closed contact crl 11 x. The cam drum 45 is angularly moved from the position 81 to the position 82, so that the tool spindle 10 is indexed to the predetermined angular position.

The relay CR111, when energized, causes a well-known tool exchange control circuit TECC to operate the exchange arm 13 because its normally open contact curl 11 is provided therein as a start instruction. Therefore, the exchange arm 13, as previously mentioned, simultaneously grips the fresh and used tools 11, 11, removes the tools 11, 11 from the tool magazine 24 and the tool spindle 10 after the tool unclamping operation is carried out with the tool spindle 10, rotates through an angle of 180 degrees, and inserts the tools 11, 11 respecitvely, into the tool magazine 24 and the tool spindle 10. Upon the completion of the tool insertion operation, the tools are still being gripped by the grippers 13a, 13b, whose gripping force is, however, temporarily weakened, and in this connection, a magnetic relay CR135 is then energized through normally open contacts crl 11, crl 12 and cr128 and a normally closed contact cr136x. The energization of the relay CR135 operates the index motor 46 again so as to further rotate the cam drum 45, whereby positive engagement is brought about between the drive key 1 Oa and the key-way 1 la of the fresh tool 11.

When a normally open contact lsl of the limit switch LS1 is closed, a magnetic relay CR136 is energized to de-energize a magnetic relay CR113 and the relay CR135 by opening its normally closed contacts cr 136x. Thus, the fresh tool 11 is clamped upon the tool spindle 11, and the index motor 46 is de-energized so as to cause the clamping claws 43a, 43b to remain opened and thereby to allow the rotation of the tool spindle 10. When the tool clamping operation is completed, a limit switch LS5 is activated, a normally open contact ls5 of which is therefore closed, to energize a magnetic relay CR137. A normally closed contact cr137x of the relay CR137 is thus opened to deenergize the relay CR112, whereby the tools 11, 11 are released from the exchange arm 13. As the completion of the tool release operation results in closing a limit switch contact ls6, a magnetic relay CRFM06 is energized to deenergize the relays CR111 and CR136 by opening its normally closed contacts crFM06x and crFM06x. The energization of the relay CRFM06 is regarded as a complete instruction of the auxiliary function M06, so that, as mentioned above, another machining operation is initiated from this stage.

Figure 9 shows another fine indexing mechanism modified from that shown in Figure 4. In this modification, a cam drum 45, disposed with its axis extending tangentially of the tool spindle 10, is provided with a cam way, along which the index protrusion 41a is directly guided. As shown in the development plan of Figure 10, the cam way is defined by one cam slot 45c, which effects upon the index protrusion 41a the same indexing movement as the cam slots 45a, 45b, shown in Figure 4, do through the index claws 43a, 43b. Accordingly, it is noticed that the dimension of the cam slot 45c exactly corresponds to that of a land portion 45c' defined, as shown in Figure 4, by the cam slots 45a, 45b.

Obviously, other modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein.

WHAT WE CLAIM IS: 1. In a machine tool with an automatic tool exchanger having a tool spindle supported for rotation about a longitudinal axis and capable of receiving a tool at one end thereof, a tool magazine for removably storing a plurality of tools, and exchange means for exchanging tools between the tool spindle and the tool magazine, the improvement comprising: a drive key protruding from one end of the tool spindle and engageable, with a predetermined rotational play, with a key-way formed on each of the tools; a plurality of detents on the tool magazine respecitvely engageable with and disposed in position to orientate the key-ways of the tools in the same angular direction as one another when engaged respectively with the key-ways of the tools, each of the detents having substantially the same width as that of the drive key in the rotational direction; coarse indexing means for indexing the tool spindle within a predetermined angular extent after a machining operation; and fine indexing means comprising a movable cam member operably

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

30, and then, the grippers 13a, 13b are opened to release the tools 11, 11. The spindle head 21 is immediately moved toward the machining position and, at the same time, the spindle drive motor 37 is operated to rotate the tool spindle 10 in the counterclockwise direction.

Accordingly, another machining operation is initiated in such a condition that the fresh tool 11 is positively and certainly driven by the drive key lOu.

Figure 8 shows a portion of an electric control circuit employed to accomplish the above-described operation. When a normally open contact cr100 is closed, upon the completion of the coarse indexing operation, a magnetic relay CRl lO is energized and selfheld, since a normally open contact crM06 for instructing the tool exchange operation has already been closed. The energization of the relay CR110 operates the index motor 46 to rotate the cam drum 45. When a normally open contact ls2 of the limit switch LS2 is closed, a magnetic relay CR1 11 is energized and deenergizes the relay CRl l O by opening its normally closed contact crl 11 x. The cam drum 45 is angularly moved from the position 81 to the position 82, so that the tool spindle 10 is indexed to the predetermined angular position.

The relay CR111, when energized, causes a well-known tool exchange control circuit TECC to operate the exchange arm 13 because its normally open contact curl 11 is provided therein as a start instruction. Therefore, the exchange arm 13, as previously mentioned, simultaneously grips the fresh and used tools 11, 11, removes the tools 11, 11 from the tool magazine 24 and the tool spindle 10 after the tool unclamping operation is carried out with the tool spindle 10, rotates through an angle of

180 degrees, and inserts the tools 11, 11 respecitvely, into the tool magazine 24 and the tool spindle 10. Upon the completion of the tool insertion operation, the tools are still being gripped by the grippers 13a, 13b, whose gripping force is, however, temporarily weakened, and in this connection, a magnetic relay CR135 is then energized through normally open contacts crl 11, crl 12 and cr128 and a normally closed contact cr136x. The energization of the relay CR135 operates the index motor 46 again so as to further rotate the cam drum 45, whereby positive engagement is brought about between the drive key 1 Oa and the key-way 1 la of the fresh tool 11.

When a normally open contact lsl of the limit switch LS1 is closed, a magnetic relay CR136 is energized to de-energize a magnetic relay CR113 and the relay CR135 by opening its normally closed contacts cr 136x. Thus, the fresh tool 11 is clamped upon the tool spindle 11, and the index motor 46 is de-energized so as to cause the clamping claws 43a, 43b to remain opened and thereby to allow the rotation of the tool spindle 10. When the tool clamping operation is completed, a limit switch LS5 is activated, a normally open contact ls5 of which is therefore closed, to energize a magnetic relay CR137. A normally closed contact cr137x of the relay CR137 is thus opened to deenergize the relay CR112, whereby the tools 11, 11 are released from the exchange arm 13. As the completion of the tool release operation results in closing a limit switch contact ls6, a magnetic relay CRFM06 is energized to deenergize the relays CR111 and CR136 by opening its normally closed contacts crFM06x and crFM06x. The energization of the relay CRFM06 is regarded as a complete instruction of the auxiliary function M06, so that, as mentioned above, another machining operation is initiated from this stage.

Figure 9 shows another fine indexing mechanism modified from that shown in Figure 4. In this modification, a cam drum 45, disposed with its axis extending tangentially of the tool spindle 10, is provided with a cam way, along which the index protrusion 41a is directly guided. As shown in the development plan of Figure 10, the cam way is defined by one cam slot 45c, which effects upon the index protrusion 41a the same indexing movement as the cam slots 45a, 45b, shown in Figure 4, do through the index claws 43a, 43b. Accordingly, it is noticed that the dimension of the cam slot 45c exactly corresponds to that of a land portion 45c' defined, as shown in Figure 4, by the cam slots 45a, 45b.

Obviously, other modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practised otherwise than as specifically described herein.

WHAT WE CLAIM IS: 1. In a machine tool with an automatic tool exchanger having a tool spindle supported for rotation about a longitudinal axis and capable of receiving a tool at one end thereof, a tool magazine for removably storing a plurality of tools, and exchange means for exchanging tools between the tool spindle and the tool magazine, the improvement comprising: a drive key protruding from one end of the tool spindle and engageable, with a predetermined rotational play, with a key-way formed on each of the tools; a plurality of detents on the tool magazine respecitvely engageable with and disposed in position to orientate the key-ways of the tools in the same angular direction as one another when engaged respectively with the key-ways of the tools, each of the detents having substantially the same width as that of the drive key in the rotational direction; coarse indexing means for indexing the tool spindle within a predetermined angular extent after a machining operation; and fine indexing means comprising a movable cam member operably

supported and provided with a first cam segment for indexing the tool spindle to a predetermined angular position in a first movement of the cam member and a second cam segment for rotating the tool spindle a predetermined angular distance from the predetermined angular position in a second movement of the cam member, so as to bring about a positive drive engagement between the key and the key-way provided respectively on the tool spindle and a fresh tool, and cam drive means connected to the cam member for generating the first movement of the cam member after the tool spindle is indexed by the coarse indexing means and for generating the second movement of the cam member after the fresh tool is inserted into the tool spindle by the exchange means.
2. A machine tool as set forth in Claim 1, wherein the cam member is a cam drum disposed to be rotatable about an axis extending tangentially of a circle centred on the axis of the tool spindle, and wherein the cam drive means comprises a drive motor for rotating the cam drum selectively through the first and second movements.
3. A machine tool as set forth in Claim 2, wherein the first and second cam segments are formed upon the circumferential surface of the cam drum and communicated with each other.
4. A machine tool as set forth in Claim 2 or 3, wherein the fine indexing means further comprises an index protrusion provided upon the tool spindle to be protruded radially thereof, the cam drum being drivingly connectable to the index protrusion so as to adjust the angular position thereof in accordance with the first and second cam segments.
5. A machine tool as set forth in Claim 4, wherein the first cam segment is formed to gradually narrow the rotatable angular extent of the index protrusion as the angular position of the cam drum advances, so as thereby to index the tool spindle to the predetermined angular position, and wherein the second cam segment is extended helically of the cam drum.
6. A machine tool as set forth in any one of Claims 2 to 5, wherein the cam drum is further provided with a third cam segment communicating from the second cam segment to the first cam segment and formed to gradually release the index protrusion from the restraint by the cam drum.
7. A machine tool as set forth in Claim 2 or 3, wherein the cam drum is provided with two closed cam slots on each of which the first and second cam segment are defined, and wherein the fine indexing means further comprises guide means extended in parallel relation with the axis of the cam drum, an index protrusion provided upon the tool spindle to be protruded radially of the same, and a pair of indexing claws slidably guided on the guide means and respectively engaged with the closed cam slots so as to be selectively opened and closed, the indexing claws being connectable with the index protrusion to index the tool spindle to the predetermined angular position when closed and to permit the rotation of the tool spindle when opened.
8. A machine tool as set forth in Claim 7, wherein the first cam segments defined on both of the cam slots gradually approach each other as the angular position of the cam drum advances, so as to move the indexing claws from an open condition to a closed condition, and wherein the second cam segments defined on both of the cam slots are extended helically of the cam drum with a parallel relation, so as to allow the indexing claws to integrally move along the guide means as the indexing claws remain in the closed condition.
9. A machine tool as set forth in Claim 7 or 8, wherein the cam slots respectively define thereon third cam segments communicating from the second cam segments to the first cam segments and gradually separating from each other so as to release the index protrusion from the restraint by the indexing claws.
10. A machine tool as set forth in any one of the preceding claims, wherein the fine indexing means further comprises control means for controlling the operation of the drive motor, the control means comprising: first and second detectors for respectively detecting the open and closed condition of the indexing claws, a first control circuit for energizing the drive motor until the second detector is activated, after the tool spindle has been indexed within the predetermined angular extent by the coarse indexing means, and a second control circuit for energizing the drive motor until the first detector is activated, after the fresh tool has been inserted into the tool spindle by the exchange means.
11. In a machine tool with an automatic tool exchanger having a tool spindle supported for rotation about a longitudial axis and capable of receiving a tool at one end thereof, a tool magazine for removably storing a plurality of tools, and exchange means for exchanging tools between the tool spindle and the tool magazine, the improvement comprising: a key provided on one of the tool spindle and each of the tools for drive engagement with a key-way provided on the other of the tool spindle and each of the tools, the key and the key-way being so sized as to establish a predetermined rotational play permitting a substantial relative rotation therebetween when engaged with each other; a plurality of means on the tool magazine each engageable with one of the key and the key-way provided on each of the tools and disposed in position to orientate the keys or the key-ways provided on the tools when engaged respectively with the keys or the keyways provided on the tools, each of the means having substantially the same width as that of one of the key and the key-way provided on the tool spindle in the rotational direction; coarse indexing means for indexing the tool spindle within a predetermined angular extent after a machining operation; and fine indexing means provided with a movable cam member for indexing the tool spindle to a predetermined angular position upon completion of indexing the tool spindle by the coarse indexing means within the predetermined angular extent and further for indexing the tool spindle from the predetermined angular position through at least an angular distance after a fresh tool selected from the tools is inserted by the exchange means into the tool spindle, so as to bring about a positive drive engagement between the key and the key-way provided on the tool spindle and the fresh tool.
12. A machine tool as set forth in Claim 11, wherein the fine indexing means comprises means provided on the tool spindle for integral rotation therewith, the movable cam member drivingly engage able with the means on the tool spindle only when the tool spindle is within the predetermined angular extent, and drive means connected to the movable cam member for effecting a first rotational movement of the movable cam member so as to index the tool spindle to the predetermined angular position and further for effecting a second rotational movement of the movable cam member so as to index the tool spindle from the predetermined angular position through at least the angular distance.
13. A machine tool as set forth in Claim 12, wherein the drive means comprises a drive motor connected to the movable cam member, a first control circuit for controlling the drive motor to effect the first rotational movement of the movable cam member upon completion of indexing the tool spindle by the coarse indexing means within the predetermined angular extent, and a second control circuit for controlling the drive motor to effect the second rotational movement of the movable cam member after the fresh tool is inserted into the tool spindle by the exchange means.
14. A machine tool as set forth in Claim 11, 12 or 13, wherein the key and the key-way are provided respectively on the tool spindle and each of the tools, and wherein the plurality of means provided on the tool magazine are detent members engageable respectively with the key-ways of the tools so as to hold the same in a corresponding angular relation to the predetermined angular position.
15. A machine tool as set forth in Claim 14, wherein the fine indexing means includes only one drive motor for positively driving the movable cam member, and wherein the coarse indexing means is free from any drive motor, but includes brake means for stopping within the predetermined angular extent the tool spindle which continues rotation under the action of its inertia.
16. A machine tool with an automatic tool exchanger having a tool spindle supported for rotation about a longitudinal axis for receiving and driving a tool, a tool magazine for removably storing a plurality of tools and an exchange arm for exchanging tools between the tool spindle and the tool magazine, the tool spindle on the one hand and each of the tools on the other hand having respectively first and second components of keying means, interengage able with a predetermined rotational play, for providing positive drive engagement between the tool spindle and the tool received by the tool spindle, the tool magazine having at each of its tool storage positions locating means co-operating with the tool's component of the keying means so that the tools all enter and leave the tool magazine with substantially the same angular orientation corresponding to a predetermined angular position of the tool spindle for tool changing, the machine tool including a coarse indexing device for stopping the tool spindle, after a machining operation, within a predetermined angular extent within which the tool changing position lies, and a fine indexing device comprising a movable cam member provided with drive means for indexing the tool spindle to the predetermined angular position, when it has been stopped within said range, and also for indexing the tool spindle through an angular distance from the predetermined angular position, upon insertion of a fresh tool, so as to bring the two components of the keying means into positive drive engagement.
17. A machine tool as set forth in Claim 16.

wherein the first and second components of the keying means comprise, respectively, a drive key protruding from the tool spindle and a key-way formed on each of the tools, the key and key-way being dimensioned to allow for said rotational play.
18. A machine tool as set forth in Claim 17, wherein each of the locating means comprises a detent pin of substantially the same width as the drive key.
19. A machine tool as set forth in Claim 17 or 18, including any of the features or combinations of features set forth in any of Claims 12 to 15.
20. A machine tool as set forth in Claim 16, 17 or 18, wherein the cam member has a first cam segment for the indexing to the predetermined angular position in a first movement of the cam member and a second cam segment for the indexing into positive drive engagement in a second movement of the cam member.
21. A machine tool as set forth in Claim 20, including any of the features or combinations of features set forth in any of Claims 2 to 10.
22. A machine tool, substantially as described with reference to the accompanying drawings.