Abstract:
A coolant nozzle is used on a machine tool having a rotating bit of convoluted longitudinal profile for cutting a number of slots in a disk. The nozzle includes at least one coolant inlet and at least one coolant outlet. The coolant outlet has a convoluted section and is positioned to direct a coolant stream tangentially at the bit in a direction of rotation of the bit. Internal surface portions of the nozzle define one or more passageways between the inlet and the outlet(s).

Description:
BACKGROUND OF THE INVENTION 
   (1) Field of the Invention 
   The invention relates to machining. More particularly, the invention relates to the machining of blade attachment slots in turbomachine disks. 
   (2) Description of the Related Art 
   In turbomachines such as gas turbine engines, the blades of fan, compressor, and turbine sections may be secured to separate disks. One attachment means involves providing blade roots having a convoluted section complementary to a convoluted section of slots in the disk periphery. An exemplary configuration involving a convoluted profile that generally increases in transverse dimension from the slot base toward its opening is called a fir tree configuration. A number of methods have been used or proposed for forming the slots. Exemplary methods are discussed in S. L. Soo et al., “Point Grinding of Nickel-Base Superalloys”, Industrial Diamond Review, February 2002, pages 109–116. In such a system, the introduction of coolant/lubricant is extremely important. 
   SUMMARY OF THE INVENTION 
   Accordingly, one aspect of the invention involves a coolant nozzle for use on a machine tool having a rotating bit of convoluted longitudinal profile for cutting a number of slots in a disk. The nozzle includes at least one coolant inlet and at least one coolant outlet. The coolant outlet has a convoluted section and is positioned to direct a coolant stream tangentially at the bit in a direction of rotation of the bit. Internal surface portions of the nozzle define one or more passageways between the inlet(s) and outlet(s). 
   In various implementations, the internal surface portions may be formed in a laser sintered ceramic body. The nozzle may have a guide surface positioned to direct the coolant stream toward the slots so that with the bit aside the slot between the disk and the outlet, the coolant stream passes laterally between the bit and the guide surface. There may be first and second outlets on first and second sides of a disk-receiving space. The nozzle may be shiftably mounted to permit the nozzle to be shifted between an operative condition wherein the nozzle blocks longitudinal extraction of the disk from the machine and a clear condition wherein the nozzle does not block such extraction. 
   Another aspect of the invention involves a coolant nozzle for use in a machine tool having a rotating bit for shaping a slot in a workpiece. The nozzle includes a gap for accommodating the workpiece in an operative position. The nozzle includes at least one coolant inlet. The nozzle includes first and second coolant outlets positioned to direct first and second coolant streams toward the workpiece from first and second sides of the workpiece. The nozzle includes first and second guide surfaces positioned to direct the first and second coolant streams toward the slot. 
   In various implementations, the guide surfaces may face in substantially opposite directions. The guide surfaces may have convoluted sections corresponding to convoluted sides portions of the slot as shaped by the bit. The outlets may have convoluted sections corresponding to the side portions of the slot. First and second guide surfaces and first and second outlets may be on respective first and second arms of a single sintered ceramic element. 
   The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a view of a coolant nozzle in accordance with principles of the present invention in an operative position relative to a blade disk and a machine tool spindle. 
       FIG. 2  is a first view of the nozzle of  FIG. 1 . 
       FIG. 3  is a second view of the nozzle of  FIG. 1 . 
       FIG. 4  is an end-view of a first outlet end surface of the nozzle of  FIG. 1 . 
       FIG. 5  is an end-view of a second outlet end surface of the nozzle of  FIG. 1 . 
       FIG. 6  is a sectional view of the nozzle of  FIG. 1  taken along line  6 — 6  of  FIG. 1  showing a machine tool bit in a first subsequent stage. 
       FIG. 7  is a sectional view of the nozzle and bit of  FIG. 6  in a second subsequent stage. 
     Like reference numbers and designations in the various drawings indicate like elements. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a machine tool spindle  20  carrying a bit  22  (e.g., an abrasive quill) for rotation in a direction  500  about a spindle axis  502 . The tool is used to machine a series of blade retention slots from slot precursors  30  extending inward from the periphery  32  of a blade disk  34 . The disk may be held in a fixture (not shown) for controlled rotation about its axis  504 . The tool may reciprocally translate the spindle along an axis  506  transverse to the axis  502  to machine the slots. In an exemplary embodiment, the slots are ground from slot precursors having stepped sidewalls, although they may alternatively be ground directly from an uninterrupted periphery. The slot precursors (smaller clearance slots) may initially be ground by a stepped grinding wheel (not shown) and then enlarged/reconfigured by the bit  22 .  FIG. 1  further shows a coolant delivery system  40  having a nozzle  42 . The nozzle  42  comprises a selective laser sintered (SLS) nozzle body  44  having first and second outlet arms  46  and  48 . A gap or space  50  between the distal ends of the arms receives the disk when the disk and nozzle are in their operative positions. The nozzle may be mounted for movement transverse to the disk such as along a direction  510  by a sliding gantry mechanism  52  supporting the nozzle relative to the tool. 
     FIGS. 2 and 3  show further details of the nozzle  42 . Each of the arms  46  and  48  has a distal end surface  60 ,  61 . Each of these surfaces has an opening  64 ,  65  at least partially corresponding to a profile of the slots  30 . Extending inboard from the opening  64 ,  65  along an end portion  66 ,  67  of the associated arm are surfaces  68 ,  69  which extend to associated inboard surfaces  70 ,  71  of the end portions. Spaced inboard of the end portions are respective outlet end surfaces  74 ,  75  having outlet apertures  78 ,  79 . One or more passageways connect the outlet apertures to one or more coolant inlets. In the exemplary embodiment, the nozzle includes respective first and second coolant inlets  82  and  84  to which are connected appropriate fittings and coolant conduits (not shown). The first outlet aperture  78  has conjoined first and second portions  86  and  87 . The first portion  86  ( FIG. 4 ) has a perimeter with an outboard portion  88  and a segmented inboard portion  89  generally parallel to and slightly spaced apart from each other. The first portion  86  is formed in a convoluted profile corresponding at least partially to a profile of the bit and thus of the slot once machined. The second portion  87  has a perimeter with an inboard portion  90  and a segmented outboard portion  91 . Segments of the outboard portion  91  face and at their ends join segments of the inboard portion  89  where the two outlet portions join. The second portion  87  is formed with a stepped convoluted profile corresponding at least partially to the profile of the slot precursor. The second outlet aperture  79  ( FIG. 5 ) has a perimeter with outboard and inboard portions  94  and  96  also generally parallel to and slightly spaced apart from each other. In the exemplary embodiment, the outlet aperture  79  and the first portion  86  of the outlet aperture  78  extend along both sides of the bit profile near what would be the tip of the bit and then along only one side along substantially an entire grinding length of the bit. This particular side is chosen so that respective second and first coolant jets  102  and  100  ( FIG. 6 ) expelled from the first outlet aperture impact tangentially with the rotation of the bit (rather than against such rotation) along this side. 
     FIG. 6  specifically shows the bit in an intermediate stage of its traversal along a direction  520 . The bit has passed from a second receiving bay  106  into a channel defined by the surface  69 . In this stage, coolant from the second nozzle aperture  79  impacts the bit as described above, guided by the surface  69  on the first side, however, due to the presence of uncut slot precursor, coolant from the first nozzle aperture  78  first portion  86  (a portion of a jet  100 ) does not effectively enter the slot precursor and is deflected by the disk first side  108 . Coolant from the second portion  87  (the second portion of that jet  100 ) can substantially enter the slot precursor and cool the approaching bit, although impacting slightly less tangentially. In  FIG. 7 , the bit has passed out of the channel and spanned the gap between the nozzle and the disk and penetrated the second side  110  of the disk to begin to cut the slot from the precursor. As the bit passes further down the channel toward the disk, the surfaces  69  (in particular, that portion on the side aligned with the outlet) tends to further guide the jet  102  to the bit. Eventually, the bit will come out the first side  108  of the disk and enter the channel defined by the guide surfaces  68  and reach the first receiving bay  104 . Once the bit passes all the way through the first side  108 , the portion of the jet  100  from the first outlet aperture first portion  86  can tangentially impact the bit as described above. Thereupon, the bit/spindle may be retracted and traversed in opposite the direction  520  and reinserted into the second bay. Alternatively it may retraversed back through the machined slot. The disk may then be incrementally rotated to bring the next slot precursor into an operative position, whereupon the procedure is repeated. 
   One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, details of the slot to be ground and of the machine with which the nozzle is used may influence details of any implementation. Accordingly, other embodiments are within the scope of the following claims.