Abstract:
A unitary punch and die assembly for tooling a powder material compacting apparatus, or press, the assembly comprising a die plate mounted in the press table, which removably holds a die bushing clamped in position by a threaded retainer provided with a peripheral thread of the buttress type, and a punch removably supported in a punch holder plate actuatable along guideposts supported by the die plate. A second plate slidably mounted in the guideposts and reciprocated by the press ram is rigidly interconnected with the punch support plate for reciprocation thereof. For compacting articles such as toroidal articles, cylinders, and the like, a core rod supported by an appropriate support plate adjustably fastened on the guide posts projects through a longitudinal bore provided in the punch and punch support plate.

Description:
CROSS-REFERENCE TO RELATED PATENTS 
     The present application is an improvement on the punch and die assemblies for compacting powder material disclosed in and claimed in U.S. Pat. Nos. 3,640,654, 3,669,582, 3,671,157, 3,775,032 and 3,805,370, all assigned to the same assignee as the present application. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to powder material compacting presses, more particularly to an improved die and punch assembly for powder compacting presses. 
     In powder compacting presses as disclosed in U.S. Pat. Nos. 3,328,840; 3,344,213, 3,328,842; 3,414,940; 3,561,054; 3,726,622; 3,741,697; 3,775,032; 3,805,370 and 3,822,974, all assigned to the same assignee as the present application, there are disclosed apparatus such as presses and tools for such presses for compacting powder material, such as powdered metal, ferrite, glass and other materials into diverse articles such as toroids, beads, pellets and the like. In the powder compacting apparatus disclosed in the aforementioned patents, the articles are formed in single or multi-cavity dies, in which reciprocable punches are disposed, by compaction of the powder material between the punch end face and an anvil displaceable over the die cavity so as to overlap the die cavity. 
     A work station positioner assembly, forming part of the press apparatus, is disposed angularly or linearly movable over the die plate and is provided with three separate or integral elements, a powder dispenser unit, an anvil, and a pick-up head. The powder dispenser unit is first positioned over the die cavity to fill the die cavity with a predetermined amount of powder material. The dispenser unit is then removed from above the work station positioner assembly, and the anvil unit is in turn positioned over the die cavity and clamped in position. The punch is reciprocated upwardly in the die such as to compact the powder material between the punch end face and the anvil. The anvil is then unclamped from above the die cavity and replaced by the pick-up head as a result of further angular or linear motion of the work station positioner assembly. The punch is reciprocated upwardly so as to eject the compacted article from the die cavity into the pick-up head for transfer to a remote station, or, alternatively, for transfer to a collection station by subsequent motion of the work station positioner assembly. 
     By way of utilizing standardized punch and die assemblies in the form of interchangeable tool capsules, all adapted to be interchangeably mounted on the press table in an appropriate mounting aperture, with the die plate disposed in the mounting aperture and held therein by any convenient means such as by mounting bolts, the remaining of the tool capsule projecting below the press table, with the punch actuating mechanism of the press appropriately connected to the punch actuating plate portion of the tool capsule, it is a simple matter after a production run of a particular part to remove a tool capsule and replace it by another tool capsule for compacting a different part. With the exception of the die bushings, the punches, and the core rods, if any, all the other mechanical parts forming the tool capsule are subject to little or no wear. The die bushings, the punch and the core rods, if any, are however, subject to important load stresses and to wear, as a result of which they may experience dimensional changes, such as a progressive opening of tolerances, and, if subjected to abnormal loads, they may be damaged beyond repair or even break. It is therefore convenient for the user to provide a tool capsule which can be easily dismantled and which provides easy removal of the die bushings, punches and core rods, when they become worn or when they break, for replacement by new die bushings, punches and core rods. It is also desirable that replacement die bushings, punches and core rods be reinserted in the tool capsule without too much fuss, without requiring complicated fixtures and gauges, and that the diverse replacement elements be held securely in position in proper alignment, as lack of alignment and incorrect positioning may result in breakage or in obtaining finished parts not conforming to specifications. 
     SUMMARY OF THE INVENTION 
     The present invention provides a punch and die assembly, or tool capsule, for powder material compacting presses, with convenient means for removably holding the perishable tool portions of the assembly such as to provide convenient replacement when such perishable tool portions, such as the die bushings, the punches and the core rods, if any, become unserviceable. More particularly, the present invention provides means for holding the die bushing, or bushings, in the die plate by means of a threaded retainer ring provided with a thread of the buttress type engaged with the die bushing support block, such that the die bushing is held securely in position by the retainer ring, in perfect alignment with respect to the punch axis, without shims, gauging or special precautions. 
     A better understanding of the present invention will be had by those skilled in the art when the following description of one of the best modes contemplated for practicing the invention is read in conjunction with the drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a top plan view of a punch and die assembly, or tool capsule, according to the present invention; 
     FIG. 2 is a sectional view along line 2--2 of FIG. 1; and 
     FIG. 3 is a detailed schematic view of the buttress type thread used for removably holding the die retainer ring in the die mount of the tool capsule of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1-2, and more particularly to FIG. 2, a punch and die assembly, or tool capsule 10, according to the present invention, comprises a die plate 12 adapted for mounting in an aperture 14 in the table 16 of a powder compacting apparatus, or press (not shown), for example by means of bolts or other holding means, not shown, passed through mounting holes 17 in a die plate spacer member 18. The die plate spacer 18 is mounted below the die plate 12 and attached to the die plate 12 by means of countersunk screws 20 (FIG. 1). At least one, and preferably a pair of guideposts 22 extending parallel to each other and perpendicular to the die plate 12, slidably support and guide a punch support upper plate 24 and a punch actuating lower plate 26, disposed parallel to each other and in a spaced apart relationship. The guideposts 22 are fixedly supported by the die plate spacer member 18 as a result of an end of each guidepost 22 being press fitted in a bore 28 in the die plate spacer member 18. Radially disposed set screws, not shown, may be used to further secure the end of the guideposts 22 in the bore 28. 
     The punch actuating lower plate 26 is provided with a downwardly projecting integral portion 30 for coupling to the reciprocal ram of the press, not shown. The punch actuating lower plate 26 and the punch support upper plate 24 is interconnected by means of a pair of vertically disposed spacer sleeves 32, a threaded connecting rod 34 being disposed within each sleeve 32, such as to rigidly interconnect the punch actuating lower plate 26 and the punch support upper plate 24, which are thus reciprocable in unison. 
     The punch support upper plate 24 has an axially disposed stepped bore 36, having its larger diameter portion disposed toward the die plate spacer member 18. A punch support insert 38 is disposed in the stepped bore 36, the punch support insert 38 having an annular step portion 40 engaged with the annular step portion 42 of the bore 36. A punch member 44 has an enlarged foot portion 46, engaged with the upper face 48 of the punch support insert 38, which is held in position above the punch support insert 38 by means of a clamping plate, or retainer, 50 held by clamping screws 52. The upper free end of the punch 44 is engaged in the bore 54 of a die bushing 56, disposed in an aperture or bore 58 formed in the die plate 12. The die plate bore 58 has a reduced diameter portion 60 accepting the reduced diameter portion 62 of the die bushing 56, an annular surface 64 formed in the periphery of the die bushing 56 at the junction between its reduced diameter portion 62 and its main body portion 66 being engaged with a corresponding annular surface 68 formed in the die plate bore 58. 
     The die plate spacer member 18 is provided with a threaded bore 70 in which is engaged a die bushing retainer 72 having a peripheral thread 74 engaged with the thread of the threaded bore 70 in the die plate spacer member 18. At least a pair of recesses 76 disposed in the lower face 78 of the die bushing retainer 72 provides a convenient means, by way of an appropriate spanner having tangs or pins engageable in the recesses 76, for rotating the die bushing retainer 72, thus clamping the die bushing 56 in position in the die plate bore 58. When clamped in position, the lower end face 80 of the die bushing 56 engages an annular recessed surface 82 formed on the end face of the die bushing retainer 72 disposed toward the die bushing 56. One or more set screws 83 disposed in a radial threaded bore 85 in the die plate spacer 18 are used for immobilizing the die bushing threaded retainer 72 relative to the threaded bore 70 in the die plate spacer 18. The end of the set screw 83 is preferably provided with a nylon or delron insert 87 preventing distorting the male thread 74 on the periphery of the die bushing retainer 72. 
     In the structures as that illustrated in the drawing, in which the tool capsule 10 is also provided with core rods, such as core rod 84 having an end projecting through an axial bore 86 in the punch 44 and an aligned axial bore 88 in the punch support insert 38, the assembly also comprises a core rod support plate 90 adjustably mounted on the guide posts 22 and between plates 24 and 26 by means of parallel bores 92 each affording passage to one of the guideposts 22, appropriate set screws, not shown, being radially disposed in the core rod support plate 90 for immobilizing the core rod support plate 90 relative to the guideposts 22 in an appropriate fixed position. The core rod support plate 90 has a stepped insert 94 disposed in a stepped bore 96 in the core rod support plate 90, the insert 94 being provided with an axial bore 98 accepting, with clearance, the body 100 of the core rod 84. 
     The core rod 84 is provided with an enlarged foot portion 102 which, after the core rod 84 has been inserted through the bore 98 of the insert 94, engages the lower surface of the insert 94. The core rod 84 is held in position in the core rod plate 90 by means of a clamp plate 104, held in position by convenient means such as screws or bolts, not shown, and provided with a recess 106 accepting the enlarged foot portion 102 of the core rod 84, a resilient washer or disc 108 made of preferably a resilient plastic material such as nylon or the like being disposed between the end face of the enlarged foot portion 102 of the core rod and the bottom surface 110 of the recess 106, for the purpose of compensating for any misalignment which may cause the core rod to bind in the bore 86 in the punch 44, and of cushioning any shock or abnormal load that could cause breakage of the core rod 84. 
     Referring now to FIG. 3, there is illustrated in detail the configuration of the conforming and engaged threads of the threaded bore 70 in the die plate spacer member 18 and the peripheral thread 74 on the die bushing retainer 72. The type of screw thread used is a buttress type thread wherein the driving face 120 of the thread is disposed at an angle a of substantially 7° relative to an imaginary plane 122 perpendicular to the axis 124 of the screw thread. The idle side of the screw thread, designated by numeral 126, is disposed at an angle b to the imaginary plane 122, the angle b being substantially equal to 45°. The top of the male thread 74 is truncated, as shown at 126, to provide adequate clearance between the top of the male thread 74 on the periphery of the retainer 72 and the bottom of the internal thread 70 in the die plate spacer member 18. 
     The advantages provided by utilizing such a modified buttress thread form are many as compared to, for example, conventional 60° V-threads. With a conventional 60° V-thread, any lateral displacement of the die bushing retainer 72 relative to the axis of the screw thread causes the retainer end faces, and particularly the end face 82 in engagement with the end face 80 of the die bushing 56, to no longer lie in a plane perpendicular to the axis of the screw thread 122, with the result that more pressure is applied by a side of the engaging annular surface 82 of the retainer 72 on an edge of the end face 80 of the die bushing 56 than on the edge of the end face 80 at a point diametrically opposed, such that there results a tilting force being exerted upon the die bushing 56 which prevents the die bushing from remaining axially aligned when held in the mounting bore 60 in the die plate 12. With conventional V-threads, for every lateral displacement of the retainer 72 of a unit of length, there results an error in axial alignment of the die bushing amounting to one half that unit of length. By using the buttress type thread illustrated at FIG. 3, a lateral displacement of the die bushing retainer 72 relative to the die plate spacer member 18, due to normal play and manufacturing tolerances, corresponding to a one unit of length, such as for example, 0.0001 in. results in a misalignment of the die bushing of 1/10 that value, or 0.00001 in. only. 
     Although the unitary punch and die assembly of the present invention has been illustrated and described as comprising a single die, a single punch and a single cord rod, it will be readily apparent to those skilled in the art that the single die bushing may be provided with a plurality of longitudinal bores and the punch holder plate may be arranged to support a plurality of punches each having an end projecting in one of the bores in the die bushing, or in the alternative, each die bore may be in a separate die bushing, the plurality of die bushings being each supported in the die plate by way of the retainer arrangement hereinbefore described. It will also be readily apparent that the die plate 12 and the die plate spacer member 18 may be made integral, resulting in the die plate spacer member being part of the die plate and the guideposts 22 being press fitted, or otherwise fastened, in bores formed in the die plate, perpendicular to the die plate surface and open to the bottom surface of the die plate. 
     The die plate 12, the die bushing 56, the punch 44 and the core rod 84 are preferably made of ultra-hard material such as a metallic carbide, tungsten carbide, for example. The other parts forming the die and punch assembly, or tool capsule 10, are made of steel.