Abstract:
Herein disclosed is an automatic tool exchanging system for an NC machining tool, in which a tool column stored with tools to be fed to the spindle head of the NC machining tool is adapted to move in accordance with the movement of the spindle head. The tools are transferred between a tool magazine and the tool column while the spindle head continues its machining operation.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a tool exchanging system for an NC machining tool and, more particularly, contemplates to improve the efficiency of the tool exchange thereby to shorten the standby time of the machining tool. 
     2. Description of the Prior Art 
     Before entering into the detailed description of the present invention, cursory review of the prior art will be made with reference to FIG. 1 in the accompanying drawings. 
     A machining tool 1 to which the present invention is to be applied is of the type, in which a workpiece W placed on a table 2 is machined by means of a tool T clamped by a spindle head S and in which the spindle head S is moved in various direction in accordance with the movement of the tool T. Machining tools provided with a tool storage magazine are disclosed in U.S. Pat. Nos. 3,998,338 and 4,238,034. On the other hand, the NC machining tool 1 has its body 3 equipped with a tool column 4, which is stored in advance with tools to be exchanged, so that the tools are exchanged between the column 4 and the spindle head S by the action of a tool exchanging robot 5 attached to the body 3. As a result, the column 4 has its tool exchanging position 6 fixed relative to the body 3. Therefore, the column 4 is moved in accordance with the movement of the spindle head S. On the other hand, the feed of that column 4 with the tools is conducted by carrying a tool magazine M, which is set in advance with a plurality of tools, on a transfer truck to the back of the machining tool 1. If the column 4 is moved during the machining operation, as has been described in the above, the tool exchange between the fixed tool magazine M and the column 4 is impossible. According to the prior art, therefore, the tool exchange is carried out by selecting the timing, at which the spindle head is stopped, such as the workpiece exchanging operation. In recent years, however, the workpiece exchange is advanced in automation so that the time therefore is remarkably shortened, whereas it takes much time to exchange many tools. As a result, the spindle head cannot be moved exclusively for the tool exchange to invite a disadvantage that the machining efficiency is deteriorated. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to eliminate the aforementioned disadvantage. 
     Another but major object of the object of the present invention is to provide a system for transferring tools between a tool magazine and a tool column during the machining operation of a spindle head. 
     According to a feature of the present invention, there is provided an automatic tool exchanging system for use in a tool exchanging system for an NC machining tool, in which a tool column stored with tools to be fed to the spindle head of said NC machining tool is adapted to move in accordance with the movement of said spindle head, said automatic tool exchanging system being characterized in that the tools are transferred between a tool magazine and said tool column while said spindle head continues its machining operation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will become apparent from the following description taken in conjunction with embodiments with reference to the accompanying drawings, in which: 
     FIGS. 1 to 3 are side elevations showing machining tools to be used in tool exchanging systems according to first to third embodiments of the present invention; 
     FIG. 4 is a perspective view showing an automatic exchanger which can be used with a system for exchanging tools at the most proper time selected during the machining process; 
     FIG. 5 is a side elevation showing the same automatic exchanger; 
     FIG. 6 is a top plan view of a tool magazine or the like and shows the switchback of a transfer truck; 
     FIG. 7 is a block diagram showing the summary of the program of another system; 
     FIG. 8 is a block diagram showing the construction arrangement of the corresponding system; and 
     FIG. 9 is a flow chart showing a series of the aforementioned program. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the present invention shown in FIG. 1 corresponds to the case in which the column 4 has such a slack portion 8 having a length l as is tensiled by an idler pulley 7. The column 4 is constructed to have its roller chain 9 carrying a plurality of tool boxes 10 at an equal pitch so that it can be freely slackened by means of a suitable pulley or sprocket. In the case as shown, the tool column 4 is made to run under tension upon pulleys 12, 13, 14 and 15 while being formed with the slack portion 8 by the idler pulley 7 which is elastically biased at all times in the direction of arrow 11. The rearmost pulley 13 supporting the tool column 4 is made rotatable on a pivot pin which is anchored at the floor, and a tool box 10a having come to the leading end portion of the rearmost pulley 13 is located at a tool exchanging position, in which the tools are exchanged between the tool magazine M on the ground and the column 4 and which is fixed relative to the ground. Reference numeral 16 indicates a tool exchanging robot which is placed on the ground for exchanging the tools between the column 4 and the tool magazine M. In this case, the tool exchanging robot 16 is anchored at the ground. 
     As a result, if the body 3 is moved together with the spindle head S in the directions of arrows X for the machining operations while the tools are being exchanged between the column 4 and the tool magazine M, i.e., when the tool box 10a is fixed, the tension of the column 4 is to fluctuate, but the idler pulley 7 is moved in the directions of arrows 17 in accordance with those fluctuations so that the column 4 is prevented from being slackened or tensiled to be broken. 
     In a second embodiment shown in FIG. 2, a tool exchanging robot 16a is attached to the tool magazine M so that it is carried on an unmanned transfer truck 18 together with the tool magazine M. In this case, the positions of the tool magazine M and the tool exchanging robot 16a are precisely predetermined so that the centering operation when a platform 19 is to be loaded with the magazine M or vice versa is facilitated. 
     In a third embodiment shown in FIG. 3, the tool magazine M set with a tool exchanging robot 16b is transferred from the platform 19 to a unit loading station 20 at the side of the machining tool body 3 so that it is carried on the station 20 together with the body 3. Thus, the third embodiment does not require the idler pulley or the like for tensiling the column, as is different from the foregoing first and second embodiments, and is enabled to effect the tool exchange between the magazine and the column while the body is being moved in any direction. In the third embodiment being described, the tool exchanging robot 16b may be disposed at the side of the body. 
     In all of the foregoing embodiments, after the tool magazine M has been placed on the platform 19, the unmanned transfer truck 18 can be engaged in transfer of another magazine or workpiece so that it can take care of a plurality of machining tools. The tool exchanging robot set on the ground or the tool magazine is made coactive with the NC machining tool upon reception and delivery of signals from and to a computer so that it exchanges tools as desired. It is quite natural that the tool exchange be effected upon or before a product lot switching operation, and the worn or troubled tools are exchanged by the system of the present invention. 
     In the embodiments thus far described, the constructions of the tool column and the tool magazine are deviced to achieve an efficient automatic exchange of tools. However, this purpose can also be achieved by sharing the time for the machining process. 
     In this case, as shown in FIG. 4, a tool exchanging robot 16c may be disposed at the side of the tool column 4 of the machining tool 1 so that the tools T fitted in the tool magazine M may be transferred to the column 4. Likewise the cases of the foregoing first to third embodiments, the positioning of the unmanned transfer truck 18 relative to the floor is effected by forcing the pistons 24, which are anchored at the transfer truck 18 and which are formed with conical holes 23, into engagement with the conical projections 22 which are anchored in position at a floor 21, and the positioning of the tool magazine M relative to the transfer truck 18 is effected by forcing the conical projections 27, which are formed on the upper surface of a lift 26 of the transfer truck 18, into engagement with the conical holes 25 which are formed in the bottom surface of the tool magazine M. Likewise, the positioning between the platform 19 and the tool magazine M is effected by forcing the conical projections 29, which are formed on the receiving surface 30 of the platform 19, into engagement with the conical holes 28 which are formed in the bottom surface of the tool magazine M. In any case, the state out of position is corrected by the wedge actions of the conical projections relative to the conical holes. The tools in the magazine are arranged at the righthand side A and lefthand side B with respect to a center line 31, and the exchanging robot 16c is allowed to extract the tools only at either side. Therefore, the magazine M is switched back by means of the transfer truck 18 so that its position is changed. Specifically, the transfer truck at a vacant state is first guided along an arrow 32 by a guide line 33 to go to below the platform 19 thereby to lift the tool magazine M. Then, the transfer truck is moved back in the direction of arrow 34 together while carrying the tool magazine thereon. After that, the transfer truck is guided forward in the direction of arrow 35 and backward in the direction of arrow 36. Thus, the transfer truck turns to go to below the platform 19 thereby to unload the tool magazine M onto the platform. In these ways, the magazine M is set in a reversed direction. 
     The time sharing operation of the machining process is conducted by the following procedures. FIG. 7 shows the outline of the program of the automatic tool exchanging system. FIG. 8 is a block diagram showing the construction arrangement of the corresponding devices. FIG. 9 is a flow chart showing a series of the aforementioned program. 
     The automatic tool exchanging system is controlled by a machining schedule managing subsystem, which is the main program, and is made coactive with a machining capacity managing subsystem controlling the operation of the NC machine and with an automatic workpiece transfer control subsystem relating to the operations of an automatic warehouse, an unmanned truck for effecting the warehousing and delivering operations of the warehouse and transfer devices. As to the transfer of the machining tools, that automatic tool exchanging system has relationship with a tool managing subsystem which in turn is made coactive with such an automatic tool transfer control subsystem as to provide programs for controlling the automatic warehouse for transfer and storage of the tools, the unmanned truck, the tool exchanging robot and the NC machine. Next, the system under consideration will be described in detail with reference to the flow chart of FIG. 9. The computer judges in accordance with the machining schedule managing system and the tool managing subsystem whether or not it is necessary to switch the lots at the present time. In case it is necessary to switch the lots, the tools especially for the lots are delivered from the automatic warehouse in accordance with the lot number designated. If it is unnecessary to switch the lots, it is judged whether the tool being used is broken or used up. This judgement is made in accordance with the lighting of a red lamp which is disposed in the NC machine. In case the tool is broken, a permanent tool is delivered from the automatic warehouse. The tool thus delivered is carried on the unmanned (i.e., transfer) truck so that it is transferred to the machining tool. This machining tool is driven in accordance with an NC cutting tape, which is stored with signals concerning whether it is possible or not to exchange the tool in accordance with the cutting information. In the case of the exchanging system of FIG. 4, the tool exchange is based upon the condition under which the tool column is stopped. The NC cutting tape is stored with the information concerning the capability of the tool exchange, accompanying the workpiece exchange command step or the tool exchange step between the column and the spindle center. This is handled as a set or reset signal of a predetermined flag in the computer. If the capable state of the tool exchange is confirmed, a tool exchanging command for demanding the operations of the tool exchanging robot, the tool column and so on is produced to repeat the exchanging operations until all the tools designated are exchanged. After all the tools have been exchanged, the unmanned truck starts to carry and transfer the tool magazine to the automatic warehouse. In addition to the aforementioned steps, the place to which the tool exchange information is added corresponds to all the steps, at which an inequality of the cutting time for one tool (or step) is greater than the time necessary for the tool exchange is satisfied. As a result, generally speaking, the tool exchange is effected in the spare time during the machining operation so that the tool exchanging robot exchanges the tools during the machining operation of the NC machine while being interlocked with the automatic tool exchanger. 
     As has been described hereinbefore, the present invention makes it possible to exchange the tools with the tool magazine during the machining operation of the NC machine. As a result, it is unnecessary to stop the machining operation for the tool exchange so that the machining efficiency can be remarkably improved.