Abstract:
A machine tool having a head with a rotatable spindle including an extensible bar for holding a tool and which is axially movable between fully retracted and fully extended positions with several intermediate additional machining positions established by selectively operable stops. Large diameter tools with a flange and mounting taper (as may be provided by a tool adapter which mounts the tool) may be used with complete fit of the mounting taper with a spindle taper, and backup support of the tool at the flange thereof. The machine tool includes a rotatable but axially fixed bar carrier engageable with the tool flange for holding of the flange in fixed position. Axially outward movement of the spindle bar brings the tapers into complete fit while the tool flange is held in fixed position against the bar carrier, and this avoids the need for precision tolerances between the taper gauge line and the back of the flange.

Description:
BACKGROUND OF THE INVENTION 
     This invention pertains to a machine tool having structure for backing up a tool on a reasonably large diameter for better operation while, at the same time, assuring a firm and complete fit between the taper of the tool and the spindle and a fit between the tool flange and the backup support for the tool. Additionally, the invention pertains to structure in a bar type machine wherein the bar can be extended to various operating positions for machining with small tools as well as having a retracted machining position where backup support for the large or extended length tool is provided. 
     Many machine tools have a spindle with a universally accepted taper, commonly known as an NMTBA (National Machine Tool Builders Association) taper, to receive a matching taper on a tool or tool adapter for locking the tool to the spindle in concentric relation therewith. When the machine tool is to use large cutters or extended length cutters, these tools can become much stiffer, effectively, if backed up on a reasonably large diameter. There is then the requirement that the tapers achieve a close fitting relation and, additionally, that a flange on a large tool, or a tool adapter carrying such tool, engage against a backup support to provide the stiffening of the tool. One way of accomplishing this is shown in Swanson et al U.S. Pat. No. 3,136,217 wherein a flanged tool adapter has parts carried on the shank of the tool adapter which can closely engage the spindle taper and with the tool adapter flange engaged against a relatively large diameter support on the spindle. The structure disclosed in the aforementioned patent results in some sacrifice in rigidity of the tool adapter, a relatively expensive special structure associated with the adapter, and a large flange on the spindle which may not be extended into relatively small cavities. 
     SUMMARY 
     A primary feature of the invention disclosed herein is to provide a machine tool which provides a complete fit between the tapers of the spindle and the tool as well as fit of the backup support and the flange of the tool without any modified or additional structure associated with the tool, and without a requirement of extremely close precision tolerances in the geometric relationship of the tool flange to the taper, and without a requirement of extremely close tolerances in the machine. This facilitates interchangeability of tools in machines. 
     Another feature of the invention is to provide a machine tool having a spindle with an axially movable bar positionable at various positions for machining and having a taper to receive the matching taper of a tool or tool adapter and a rotatable bar carrier axially fixed in position but rotatable with the bar and provided with a surface for support of a flange of a tool or tool adapter whereby in loading of a tool or tool adapter into the spindle the flange first engages the bar carrier prior to the tapers being in closely fitting relation and then there is axial outward movement of the bar to fully seat the tapers while the tool is held in fixed position by the flange engaging the bar carrier. 
     An object of the invention is to provide a machine tool with means to obtain a backup relation between a flange of a tool or tool adapter as well as a close fit of a spindle taper and a matching taper associated with the tool by axial movement of the spindle resulting from reaction forces between the flange and its backup support. 
     Another object of the invention is to provide a machine tool of the bar type wherein the bar has axial movement to different extended positions for machining with small tools and has a retracted machining position for using a variety of tools, including large diameter or extended length tools with there being a backup support of such tools on a reasonably large diameter. The bar has a taper to receive a matching taper associated with the tool and a rotatable bar carrier surrounding the bar and fixed against axial movement but rotatable with the bar has a surface providing a backup support for a flange associated with the tool. Means interengaging between a tool and the bar provide for axially moving the bar in a direction to closely fit the tapers of the bar and the tool while the flange of the tool is held in fixed position against the surface of the bar carrier. 
     An additional object of the invention is to provide a machine tool of the bar type wherein releasable locking means hold the bar in a desired axial position and are released during mounting of a tool into the bar and means including both fixed stops and selectively movable stops control the axial location of the bar. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a central, vertical fragmentary section of a machine tool with a head and spindle structure; 
     FIG. 1B is a view, similar to FIG. 1A and showing the right-hand portion of the spindle and associated structure and at the left-hand side having a broken vertical line for matching with a similar vertical broken line at the right-hand side of FIG. 1A; 
     FIG. 2 is a fragmentary plan section taken generally along the line 2--2 in FIG. 1B; 
     FIG. 3 is a vertical section taken generally along the line 3--3 in FIG. 1A; 
     FIG. 4 is a section through the spindle and a tool taken generally along the line 4--4 in FIG. 3, with parts broken away, showing a tool and tool adapter in initially-inserted position within the spindle; 
     FIG. 5 is a view, similar to FIG. 4, showing final positioning of the spindle parts with the tool and tool adapter; and 
     FIG. 6 is an elevational view with parts broken away of the spindle bar in extended position and carrying a small diameter tool. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The machine tool is shown generally in FIGS. 1A and 1B, with a head, indicated generally at 11, which mounts a spindle including an axially movable and rotatable bar 15 which is surrounded for part of its length by a rotatable bar carrier 16. The drive for the spindle is from a motor 20 which drives a shaft 21 supported by bearings 22 and having a pair of gears 23 and 24 for engagement with a movable gear 25 carried on an intermediate shaft 26 rotatably mounted by bearings 27 at opposite ends thereof. Two different speed ranges are provided, with one speed range obtained by mesh of the gear 25 with a gear 28 fixed to the bar carrier 16. The other speed range is provided by shift of the gear 25 to the left, as viewed in FIG. 1A, whereby a gear 29 fixed to the gear 25 for rotation therewith meshes with a larger diameter gear 30 fixed to the bar carrier 16 and with the intermediate gear 25 meshed with the gear 23 on the shaft 21. 
     The bar carrier 16 is rotatably mounted by bearings 31 at its right-hand end and by tapered roller bearings 32 adjacent its outer end and as shown at the left in FIG. 1A. Rotation of the bar carrier 16 by either of the gears 28 or 30 results in rotation of the bar 15 through a drive connection including a drive key 33 extending inwardly from the interior of the bar carrier into drive relation with an elongate drive slot 34 on the exterior of the bar 15. The drive connection causes simultaneous rotation of the bar and bar carrier while permitting axial movement of the bar 15 relative to the bar carrier 16. 
     The bar 15 is comprised of two parts 15a and 15b, with the parts being interconnected by a block 35 (FIG. 1B) secured to the left-hand end of the bar part 15b by attachment means 36 and carrying a series of bearings 37 with their inner races attached to the bar part 15a whereby the bar parts 15a and 15b are rigidly interconnected for axial movement together while permitting rotational movement of the bar part 15a while the bar part 15b is held against rotational movement. 
     The bar 15 is moved axially by a motor in the form of a cylinder 40 fixed to a stationary part 41 of the machine tool and having a rod 42 connected to an arm 43 which is secured to the right-hand end of the spindle part 15b, as shown in FIG. 1B. 
     The bar 15 has several axial positions relative to the head 11 with a pair of spaced stops 44 and 45 fixed to the frame of the head 11 for coaction with parts 35 and 46 connected to the bar 15. The part 46 has an abutment member 47 in engagement with the stop 45 when the bar 15 is in fully retracted position. When an abutment member 48 on the bar part 35 engages the stop 44, the bar is in fully extended position. There can be a series of intermediate machining positions of extension of the bar 15 provided by the selectively operable stops 49, 50 and 51. Each of these stops includes a movable plunger which can be moved to the position shown for the stop 51 to be in line with the abutment member 48 and, thus, limit the extension of the bar outwardly of the head 11. Each of the movable stops 49-51 has an actuating member 52, such as a solenoid or cylinder, associated therewith for movement of the stop between the extended position, as shown for stop 51, and the retracted position of stops 49 and 50. 
     The machine tool has means for locking the bar 15 in the retracted position or a desired position of extension controlled by any of the stops 44, 49-51 including a clamp bushing 55 mounted in a fixed frame part 56 and surrounding the bar part 15b. This bushing is known as a Speith clamp bushing wherein delivery of fluid under pressure through a line 57 causes deforming forces on the bushing elements to tightly engage the bar part 15b and lock the bar including the part 15a against axial movement. Release of the hydraulic forces releases the deformable bushing elements to free the bar for axial movement. 
     Referring to FIGS. 1A, 4 and 5, the outer end of the bar 15 is provided with a tapered opening 60, commonly referred to as an NMTBA taper to receive a matching taper on a tool to hold the tool for rotation with the bar and provide a concentric relation therebetween. This matching taper can be provided directly on the tool or, as shown in the drawings, on a tool adapter, indicated generally at 64, having a taper on a part 65 thereof. The adapter 64 has a cylindrical flange 66 with a peripheral groove 67 for handling in an automatic tool changer, as known in the art. The flange 66 provides backup support for a tool, such as a relatively large diameter cutter 68, fixed to the adapter 64. The features of the invention disclosed herein are usable with a tool having the taper and a flange or with a tool adapter having this structure and reference herein to a tool is intended to broadly cover either type of structure. 
     The inner end of the adapter 64 has a button 70 for coaction with structure mounted within the bar 15 to effect seating of the tapers. A structure of this general type to be described is generally of the type disclosed in Erikson U.S. Pat. No. 3,242,819, owned by the assignee of this application. A collet 71 with a plurality of spring fingers 72 at an end thereof is mounted within the bar 15 for movement axially thereof. A sleeve 73 fixed to the bar 15 surrounds the collet fingers 72 and has a cam surface 74 at an end thereof which coacts with cam surfaces 75 on the outer faces of said fingers to move the collet fingers 72 from a retracted position, shown in FIG. 4, to an active position, shown in FIG. 5, wherein the collet fingers engage behind the button 70. This camming movement results from movement of the collet 71 toward the right, as viewed in FIGs. 4 and 5, with there being relative movement between the collet and the bar 15. The collet 71 is normally urged to the position shown in FIG. 5 by a series of Belleville springs 80 which act between a plug 81 on the fixed sleeve 73 within the bar 15, as shown in FIG. 1B, and an annular spring seat 82 on an actuating rod 71a for the collet 71 engaging an annular member 83 fastened to the actuating rod. The rod 71a and collet fingers 72 are moved to the position of FIG. 4 against the action of the Belleville springs 80 by hydraulic means including a hollow piston 85 contained in bar part 15b and slidably mounted on rod 71a. The piston is stroke limited by an integral collar 86, whereby delivery of fluid under pressure against the right-hand surface of the piston 85 shifts the piston 85 to the left where it contacts annular member 83 with resulting leftward movement of the rod 71a and collet 71 and compression of the Belleville springs 80. 
     In mounting a tool or tool adapter with a matching taper and a flange to the spindle, the bar 15 is in fully-retracted position, with the abutment member 47 against the fixed stop 45 and the locking means 55 are released. A tool is then moved into the position shown in FIG. 4, either manually or by means of an automatic tool changer, to bring the flange 66 into abutting and supporting relation with a relatively large diameter outer face 90 of the rotatable bar carrier 16 and to make a driving engagement therebetween by fitting of drive keys 91 on the bar carrier with drive slots 92 in the adapter flange 66. This is the position shown in FIG. 4 with the collet 71 shifted to the left by force applied to the piston 85 to have the collet fingers 72 retracted. The force is then removed from the piston 85, with the result that the Belleville springs 80 are relieved from the compressive forces and urge the collet 71 toward the right, as viewed in FIGS. 4 and 5, to cause inward movement of the collet fingers 72 to engage behind the button 70 and act in a direction to move the tool toward the right, as viewed in FIGS. 4 and 5. This movement of the tool is prevented by engagement of the adapter flange 66 with the backup surface 90 of the bar carrier 16, with the result that the bar 15 moves toward the left, as viewed in FIG. 5, to bring the spindle taper 60 into close fitting relation with the matching taper 65 of the tool adapter. This action is caused by the interengaging means between the bar 15 and the tool adapter including the collet 71 and the interconnecting Belleville springs 80 and the freedom of the bar 15 to move axially. After the slight axial movement outwardly of the bar 15 to bring the tapers into close fit, the clamp bushing 55 is activated by fluid pressure through line 57 to lock the bar part 15b against axial movement which also locks the bar part 15a against such movement, but which still permits rotation of the bar part 15a  with the bar carrier 16 for machining of a part by the tool 68. During such machining, added support is provided for the tool 68 by the engagement of the adapter flange 66 with the supporting surface 90 of the bar carrier 16. 
     The outer end of the bar carrier 16 has two slots (FIGS. 4 and 5) milled into the face thereof to receive a pair of drive keys 91 (FIGS. 3, 4 and 5). The drive keys 91 are fastened by cap screws 93 and extend outwardly beyond the face 90. 
     The bar section 15a has a pair of slots (FIGS. 4 and 5) milled in its outer end to receive a pair of drive keys 100 (fastened by cap screws 100a as shown in FIGS. 3, 4 and 5) for driving relation with a flange 101 of a small tool adapter, indicated generally at 105 and as shown in FIG. 6. 
     Operation of the machine tool with the bar extended for machining with a small tool is shown in FIG. 6. 
     The tool adapter flange 66 has drive slots 92 with a radial depth sufficient to span both sets of drive keys 91 and 100, as shown in FIGS. 4 and 5. The bar drive keys 100 have a width less than the bar carrier drive keys 91 (see FIG. 3) whereby the drive keys 100 are inoperative when the bar carrier 16 is driving a large tool adapter with the flange 66. 
     The drive slots 92 in the adapter flange are of differing radial depths (see FIG. 3) and the inner ends of the drive keys 100 are at different distances from the rotational axis of the spindle whereby the tool adapter may only align with the drive keys 100 in one rotative position of the adapter. The small tool adapter 105, shown in FIG. 6, has its drive slots similarly constructed to coact with the radially offset drive keys 100 and, thus, assure mounting in only one rotative position. 
     As shown in FIGS. 3-5, the large diameter tool 68 is interconnected with the flange 66 of the adapter by pins having a round section 110 fitted in the flange and a square head 111 fitted in key slots in the tool 68.