Abstract:
A disk magazine particularly useful as a tool holder for a universal drilling and milling machine comprises a disk having a plurality of tool holders disposed at fixed intervals on the outer perimeter and a drive means for rotating the disk in steps corresponding to the spacing between the tool holders. The disk comprises a connected pair of spaced apart flat plates. In a preferred embodiment, at least one of the plates is an annular plate having recessed regions on its inner periphery and the drive means comprises a Geneva drive mechanism for engaging the recessed regions. This disk magazine can be conveniently mounted on a universal drilling and milling machine with the disk horizontal above the headstock.

Description:
FIELD OF THE INVENTION 
     This invention relates to a disk magazine tool holder particularly useful as a tool holder for a universal drilling and milling machine. 
     BACKGROUND OF THE INVENTION 
     Disk magazines are particularly useful as tool holders for automatic machine tools. A plurality of tools can be placed in a plurality of tool holders at fixed intervals around the perimeter of a rotatably mounted disk. Selected tools can then be placed in position for feeding into the automatic machine by rotating the disk through an angle determined, for example, by a machine program. Typical disk magazine tool holders are shown in German Pat. No. 1,477,492 and European Patent Disclosure Document No. 000 1 218. 
     These disk magazine tool holders, however, possess a number of disadvantages. The disk magazines are typically quite heavy, and complex, powerful and costly drives are required to effectuate their movement. 
     Accordingly there exists a need for a relatively lightweight disk magazine tool holder which can be easily mounted, driven and controlled. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a disk magazine particularly useful as a tool holder for a universal drilling and milling machine comprises a disk having a plurality of tool holders disposed at fixed intervals on the outer perimeter and a drive means for rotating the disk in steps corresponding to the spacing between the tool holders. The disk comprises a connected pair of spaced apart flat plates. In a preferred embodiment, at least one of the plates is an annular disk having recessed regions on its inner periphery and the drive means comprises a Geneva drive mechanism for engaging the recessed regions. This disk magazine can be conveniently mounted on a universal drilling and milling machine with the disk horizontal above the headstock. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The nature, advantages and various features of the invention will appear more fully upon consideration of the illustrative embodiments now to be described in detail in connection with the accompanying drawing. 
     In the Drawing 
     FIG. 1 is a side elevation showing, mounted on the headstock of a universal drilling and milling machine, a disk magazine tool holder in accordance with the invention; 
     FIG. 2 is a top view of the lower disk plate and the Geneva drive; 
     FIG. 3 is a top view of a partially cut-away section of the disk magazine; 
     FIG. 4 is a partially cut-away side elevation of the disk magazine and the actuating drive. 
    
    
     For convenience of reference the same structural elements are designated by the same reference numerals throughout the drawing. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawing, FIG. 1 shows a disk magazine tool holder 5 and a tool changer 6 mounted on the horizontal headstock 1 of a universal milling and drilling machine. In this embodiment, tool changer 6 extends in the direction of a 45 degree axis 6a and is rotatable through at least 180 degrees about this axis 6a. The headstock 1 is horizontally displaceable on a column 2. A horizontal spindle 3 is disposed at one end of headstock 1, and a drive motor 4 is at the other end. 
     Disk magazine 5 is mounted horizontally for rotation about a vertical central axis 7, which is perpendicular to the horizontal axis of spindle 3. The magazine carries a plurality of tools 9 on its outer periphery and is moved in stepwise rotation by an actuating drive 8. 
     A preferred disk magazine 5, as shown in FIGS. 2-4, comprises two separate plates such as rings 10 and 11. These rings can advantageously be punched from sheet steel two to ten millimeters thick. The rings are permanently connected together by rivets 12 and spacers 13, with a fixed spacing a between them. Both sheet-metal rings 10 and 11 have a plurality of tool holders distributed about their circumferences at fixed intervals. These tool holders comprise semicircular recesses 14 and 15 together with the spring shackles 16 on the upper sheet-metal ring 11. The spring shackles 16, pivotable upward, likewise have semicircular recesses and are provided with downwardly-pointing pawls or claws 16a at their radial end areas. The lower surfaces of the pawls or claws are beveled in different directions for engaging the radial notches or grooves in the collar of a tool shaft (not shown) and thus locating the tool 9 in magazine disk 5. A radial internal bevel on the pawls 16a draws the tool shaft into recesses 14 and 15. 
     The assembly composed of the two sheet-metal rings 10 and 11 is rigidly connected by studs 17 through the inner edge of the upper sheet-metal ring 11 to the ends of arms 18 of a support cross 19. This support cross 19 is mounted rotatably on a bridge 22 which, in turn, is permanently mounted on horizontal headstock 2. The support cross mounting is effectuated by a central bearing, composed of ball bearings 20 and a bushing 21. A radial support arm 23, for supporting actuating drive 8 and an indexing device 28, is bolted laterally to bridge 22. 
     The actuating drive 8 preferably comprises an electric motor such as a commercial automobile windshield wiper motor 24, with a vertical drive shaft 25, an intermediate gear 26, and a drive gear 27 of an associated Geneva drive, non-rotatably connected directly with intermediate gear 26. Alternatively, the drive shaft of the motor can be elastically coupled to the drive gear 27. 
     The indexing device 28, bolted to the support arm 23, preferably comprises actuating pins 29 for cooperating with nipples 30 projecting from the underside of the lower sheet-metal ring 10. This indexing device serves to control the positioning of the disk magazine, whereby a counter (not shown) determines the position of the disk magazine at any point in time by simply counting the nipples 30 which are arranged in circles. Nipples 30a, located on additional circles at larger angular spacings, of example 90°, can serve to monitor positioning and counting. 
     FIG. 2 illustrates the Geneva drive mechanism and its interaction with the lower plate of the disk. In substance, the Geneva drive comprises a rotatable drive gear or disk 27 including thereon an accentrically mounted drive pin 34 and a concentric annular guiding and locking segment 35. 
     As shown in FIG. 2, the inner edge of the lower sheet metal ring 10 is adapted for engaging this drive mechanism. Specifically, semicircular recesses 32 and radial blind slots 33, staggered at fixed angular intervals, are machined into the inner edge of the lower sheet-metal ring 10, in proportion with the spacing of the tool holders 14. Advantageously the radial slots are staggered at half the angular division between the tool holders. Pin 34 engages one of radial slots 33 during one complete revolution of drive gear 27 and thereby turns lower sheet-metal ring 10 of disk magazine 5 one step forward. 
     Annular segment 35 serves as a locking element to prevent undesirable rotation of the disk magazine. This annular segment 35 remains in a resting or sliding contact with the inner edge of semicircular recess 32 until drive pin 34 enters one of the radial blind slots 33 as drive disk 27 executes a rotary movement, and turns sheet-metal ring 10, i.e., disk magazine 5, around the rotational axis at the central bearing. The arrangement and shape of annular segment 35 and drive pin 34 are matched so that the relative position between drive gear 27 and sheet-metal ring 10 is determined b annular segment 35 in all positions in which drive pin 34 engages none of the radial slots 33. Hence, no special locking means such as socket pins or the like is required. 
     The invention is not limited to the embodiments shown. Thus, for example, in order to improve the rigidity of the complete disk, radial or circumferential stiffening ribs can be provided between the two sheet-metal rings 10 and 11. Furthermore, the upper sheet-metal ring can be made in the form of a solid circular disk, bolted directly to the central bearing. This eliminates the supporting cross. Honeycomb-shaped or corrugated stiffening elements can be located between the solid disk or the upper sheet-metal ring 11 shown and the lower sheet-metal ring 10. Such stiffening elements lead a high degree of structural rigidity to magazine disk 5 at the price of only a slight weight gain. 
     The advantage of the invention is to improve a disk magazine as a tool holder for universal drilling and milling machines in such manner that its manufacture is simplified, its weight is reduced, and the associated drives are reduced in size, without, however, having a disadvantageous effect upon the positioning accuracy. 
     The division of the disk into two separate sheet-metal plates, which can be made, for example in the form of simple punched or nibbled blanks of white metal, in addition to a substantial reduction in weight, offers the advantage of a considerable saving of material over conventional magazine disks, which are made as one-piece castings. Since each sheet-metal plate is provided at its periphery with a separate tong-shaped recess for each tool, and the two sheet-metal plates are permanently connected together with a space between them, the result is a high degree of rigidity of the disk and a sufficient axial length for reliable retention of each tool. The considerably reduced weight of the magazine disk means that a relatively small electric motor can be used as the drive assembly (a windshield wiper motor for example), whose drive shaft can be coupled directly to the drive gear of the Geneva drive without a reducing gear. The absence of a reducing gear results in further space savings. 
     Further weight savings are achieved by making the disks in the form of separate sheet-metal rings, one of which is rigidly connected to the central bearing by a support cross. 
     The use of a Geneva drive located on the inner edge of the sheet-metal ring 10 at a relatively large radial distance from the central axis permits yet a further reduction of the required torque. 
     In addition, the low weight of the magazine and the use of a bridge permit the magazine to be mounted on the headstock so that the magazine travels with it. 
     While the invention has been described in connection with a small number of specific embodiments, it is to be understood that these are merely illustrative of many other specific embodiments which can also utilize the principles of the invention. Thus, numerous and varied devices can be made by those skilled in the art without departing from the spirit and scope of the present invention.