Abstract:
A workholder arrangement which employs a support module which can have one of several different workpiece-engaging units interchangeably mounted thereon so that the same workholder module can be readily adapted to function several different ways, such as a collet chuck, a step chuck and an expanding mandrel. The support module has a housing which attaches to the basic machine tool and slidably supports therein an activating sleeve defining an interior conical surface thereon, the activating sleeve being adapted for direct connection to and being axially movable by a draw or push bar.

Description:
FIELD OF THE INVENTION 
     This invention relates to an improved workholder employing a workholder module which can be readily adapted to function as a collet-type chuck, an expandible mandrel or a step-type chuck. 
     BACKGROUND OF THE INVENTION 
     Various types of chucks and mandrels are utilized for supporting workpieces to permit machining and finishing operation to be carried out thereon. Such chucks and mandrels, herein referred to as workholders for convenience in description, are typically designed to create a specific supporting or gripping cooperation with a workpiece and, as such, several different workholders must often be provided in order to permit a wide variety of machining or finishing operations to be carried out. If such operations are to be carried out on a single machine tool, then the changing from one workholder to another is typically a rather complex and time consuming operation. In addition, a typical workholder is normally suitable solely for a very limited size range of workpiece, and the changing or modifying of the workpiece to accommodate a different size of workpiece is generally a complex and time consuming operation. 
     There is known a collet-type chuck which employs a collet employing a plurality of rubberlike segments joined to intermediate plates so as to define a collet sleeve, the sleeve having an outer conical surface which is acted on by a stationary wedging surface to effect compression of the collet sleeve into engagement with a workpiece. In this known arrangement, the forward end of the collet sleeve is acted on by an axially movable cap, the latter being axially displaced in response to rotation of an external nut. Hence, with this arrangement, both the actuating cap (which defines the front face of the chuck) and the collet sleeve are moved axially inwardly during actuation, and hence this draws the workpiece inwardly and prevents accurate axial positioning of the workpiece. 
     Accordingly, it is an object of this invention to provide an improved workholder arrangement which employs a support module which can have one of several different workpiece engaging units readily and interchangeably mounted thereon so that the same workholder module can be readily adapted to function several different ways, such as a collet chuck, a step chuck and an expanding mandrel. The improved workholder arrangement of this invention hence greatly simplifies the interchanging of the primary function of the workholder, and at the same time facilitates the interchanging of the workholder to accommodate different size ranges. 
     A further object is to provide an improved workholder arrangement, as aforesaid, which can be adapted to form a collet-type chuck employing a deformable collet sleeve constructed of an elastomeric material to enable gripping of workpieces having a wide range of sizes and properties, and the gripping of workpieces over only a short axial extent thereof. An improved workholder employing this elastomeric collet sleeve cooperates with an axially-movable actuator, such as a draw or push bar, to permit actuation of the elastomeric collet sleeve without causing axial movement thereof so as to permit accurate axial positioning of the workpiece during gripping thereof. 
     A still further object of the invention is to provide an improved workholder arrangement, as aforesaid, which employs a support module having a housing which attaches to the basic machine tool and slidably supports therein an activating sleeve defining an interior conical surface thereon, the activating sleeve being adapted for direct connection to and being axially movable by a draw or push bar. To create a collet chuck, an elastomeric sleeve is positioned within the conical bore of the activating sleeve and is restrained therein by an end cap which is threadably secured to the front end of the housing so that, upon forward axial displacement of the activating sleeve, the elastomeric collet sleeve is radially compressed inwardly for gripping the workpiece, the elastomeric collet sleeve being axially restrained by its engagement with the removable end cap. To convert to an expanding mandrel, the end cap and collet sleeve are removed, and a slidable actuator is positioned within the housing so as to abut against the forward end of the activating sleeve. The actuator has a forwardly projecting conical wedge which is received within a conical bore formed in a split cylindrical mandrel, the latter having an integral mounting plate which is threaded onto the front end of the housing. Axial displacement of the activating sleeve by the push bar, and corresponding axial displacement of the actuator causes resilient radial expansion of the mandrel for gripping a workpiece. To convert the workpiece arrangement to a step-type chuck, the mandrel and actuator are removed from the support module, following which an end cover or closer is threaded onto the forward end of the housing, and a substantially cylindrical chuck plate having a rearwardly projecting threaded stem is inserted into the activating sleeve and threadably coupled thereto. The chuck plate and closer have cooperating conical surfaces therebetween, and the chuck plate is radially split so as to be elastically radially deformed inwardly for gripping a workpiece which is positionable within a recess formed in the front face of the chuck plate. The closer also mounts thereon stop pins which project axially through openings in the chuck plate into the bottom of the workpiece-receiving recess for defining a stop surface and hence a limiting or positioning plane for the workpiece. 
     Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a central cross-sectional view of the workholder module associated with the workholder assembly of this invention. 
     FIG. 2 is a central sectional view illustrating the workholder module adapted for functioning as a collet-type chuck. 
     FIG. 3 is a fragmentary sectional view as taken substantially along line III--III in FIG. 2. 
     FIG. 4 is a view similar to FIG. 2, but showing the collet-type chuck further modified to include a workpiece stop therein. 
     FIG. 5 is an enlarged sectional view illustrating the manner in which the workpiece stop mounts within the inner end of the elastomeric collet sleeve. 
     FIG. 6 is a fragmentary sectional view taken substantially along line VI--VI in FIG. 5. 
     FIG. 7 is a central sectional view which illustrates the workpiece module modified to function as an expandable mandrel. 
     FIG. 8 is a fragmentary front view as taken substantially along VIII--VIII in FIG. 7. 
     FIG. 9 is a central sectional view illustrating the workpiece module modified to function as a step-type chuck. 
     FIG. 10 is a front view of the chuck plate illustrated in FIG. 9. 
    
    
     Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words &#34;upwardly&#34;, &#34;downwardly&#34;, &#34;rightwardly&#34; and &#34;leftwardly&#34; will refer to directions in the drawings to which reference is made. The word &#34;front&#34; will refer to the end of the workpiece assembly from which the workpiece extends, namely the rightward end in FIGS. 1, 2, 7 and 9, and the word &#34;rear&#34; will refer to the opposite end of the workpiece assembly. The words &#34;inner&#34; and &#34;outer&#34; will refer to directions toward and away from, respectively, the geometric center of the assembly and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import. 
     DETAILED DESCRIPTION 
     Referring to FIG. 1, there is illustrated a workholder module 10 according to the present invention, which module can be readily adapted to create a significant number of different workholder functions. This module includes a support sleeve or housing 11 which is adapted to be mounted on a conventional machine tool, such as a lathe. This housing 11 has a substantially cylindrical bore 12 extending coaxially therethrough. Housing 11, at its forward end 13, is externally threaded at 14. 
     An activating sleeve 15 is axially slidably supported within the bore 12 of housing 11. A set screw 16 is mounted on the housing and the end thereof projects into an axially elongated slot 17 formed in the sleeve 15 for limiting the axial displacement of the latter. Sleeve 15 defines therein a conical bore or wall 18 which is concentric with the longitudinally extending axis 27 of the workholder module, whereby the conical bore 18 diverges as it projects axially forwardly. The activating sleeve 15 defines a front end wall 19 thereon which, when the sleeve is in the rearwardmost position illustrated by FIG. 1, is spaced rearwardly from the front end wall 13 of the housing. 
     The conical wall or bore 18, at its rearward end of minimal diameter, terminates in a bore 21 which projects axially rearwardly of the sleeve, this bore 21 being internally threaded. An annular flange 22 projects axially rearwardly of the sleeve 15, which flange projects rearwardly from a shoulder 23 which is defined substantially at the rearward end of the bore 21. Flange 23 is internally threaded at 24 so as to be threadably engaged with external threads 25 formed on the forward end of an elongated activating tube 26. This activating tube 26, known as the draw or push tube as conventionally associated with a machine tool such as a lathe, is axially movable for activating the sleeve 15 in a manner which is well known. 
     Referring now to FIGS. 2 and 3, there is illustrated a collet-type chuck assembly 30 which is formed utilizing the above described workholder module. This chuck assembly is created by utilizing the module 10 and mounting thereon a collet 31 and an end cap 32. 
     The collet 31 is formed substantially as a rubber or elastic sleeve having a substantially cylindrical bore 33 extending therethrough. The collet sleeve is surrounded by an outer substantially conical wall 34 which slopes at substantially the same angle as the conical recess 18 so as to be snugly but slidably seatable therein. 
     The collet sleeve 31 is formed from a plurality of blocklike segments 35 which are disposed in a circular array, these segments being constructed of an elastomeric or rubberlike material. A plurality of metal plates or blades 36 are interposed between adjacent segments 35 and are fixed thereto, as by bonding. The metal blades 36 have the inner axially-extending edges 37 thereof projecting slightly inwardly beyond the elastomeric segments 35, and the blades similarly have the outer longitudinally extending edges 38 thereof projecting slightly outwardly beyond the elastomeric segments 35. These metal blades 36, at the axially inner ends thereof, have end portions 39 which project axially outwardly a significant extent beyond the elastomeric segments. 
     The forward axial end of the collet sleeve 31 has an annular step-like shoulder 41 which bears against the inner wall 42 of the end cap 32. This end cap 32 is of a substantially cup-shaped configuration in that it includes an annular flange 43 which is internally threaded so as to be threadably engageable with the threads 14 associated with the front end of the housing 11. This annular flange 43 has an end or base wall 44 which projects inwardly so as to partially extend across the open forward end of the housing, which base wall 44 defines thereon the inner surface 42 which acts as an abutment for the outer axial end of the sleeve collet 31. End wall 44 has a central opening 45 therethrough which is larger than the bore within the collet sleeve so as to permit a workpiece to be inserted therein. 
     To utilize the collet chuck 30 of FIGS. 2 and 3, and assuming the sleeve 15 is in the released position illustrated by FIG. 2, then a workpiece is inserted into the bore 33 of the elastomeric collet sleeve 31. Activating bar 26 is then moved axially forwardly which pushes the activating sleeve 15 forwardly. The conical surface 18 thereon reacts against the conical surface 34 of the elastomeric sleeve as defined by the outer edges 38 of blades 36, causing the latter to be resiliently compressed radially inwardly, as permitted by elastic deformation of the segments 35, so that the plurality of metal bars 36 hence have the inner edges 37 thereon moved into gripping engagement with the workpiece. Since the sleeve 31 has the front end thereof axially abutted against the end cap 32, the sleeve 31 undergoes solely radial compression, and hence the workpiece can be accurately axially positioned during the gripping engagement. 
     If the collet chuck 30 is being utilized for supporting a workpiece which must be accurately positioned and is only partially inserted into the sleeve collet, then the collet can be provided with a positive stop device 51 as illustrated by FIGS. 4-6. This stop device is positioned adjacent and mounted on the axially inner end of the collet sleeve 31. For this purpose, the stop device 51 includes an annular stop plate 52 having an axially elongated stop member 53 threadably engaged therewith and projecting coaxially therethrough, which stop member defines a workpiece-engaging stop surface 54 on the forward end thereof. The stop plate 52, in the annular periphery thereof, is provided with a plurality of axially extending grooves 55 disposed in angularly spaced relationship therearound, which grooves are aligned with and receive therein the radially inner portion of the rear part 39 of the metal blades 36, as illustrated by FIGS. 5 and 6. 
     Stop plate 52 also has an annular groove 56 formed therein and extending therearound, which groove is of substantial depth and accommodates therein a split resilient locking ring 57, the latter in its normally relaxed position being disposed so as to project slightly outwardly beyond the external periphery of the stop plate 52. This resilient lock ring 57 is designed to resiliently engage within an annular recess 58 formed in the inner edge of the rear blade part 39, which rear blade parts 39 all have a similar such recess 58 therein so as to effectively define an annular groove for accommodating the lock ring 57 as illustrated by FIG. 5. The rear corner 59 of each rear blade part 39 is also preferably rounded or chamfered. 
     The stop device 51 also preferably includes an annular washer 48 constructed of a firm rubber or elastomeric material, which washer 48 is disposed in surrounding relationship to the threaded stop member 53 directly adjacent the front face of the stop plate 52. The washer 48 is positioned so as to be supportingly disposed within the bore 33 adjacent the rearward end of the collet sleeve 31, and for this purpose the washer 48 has an outer annular wall 49 of a diameter similar to that of bore 33 so as to provide additional support for the collet sleeve adjacent the inner axial end thereof. 
     The positive stop device 51 is secured to the collet sleeve 31 when the latter is removed from the activating sleeve 15. For this purpose, the positive stop device is coaxially aligned with the rearward end of the collet sleeve 31, and the washer 48 is slidably inserted into the bore 33 of the collet sleeve, whereupon the chamfered corners 59 of the blade parts 39 cam against the split lock ring 57 and cause it to be resiliently deflected inwardly of the groove 56. The positive stop device is axially pushed further into the collet sleeve until the lock ring 57 resiliently expands so as to lockingly engage the recesses 58, and hence axially secure the positive stop device to the collet sleeve. When so secured, the threaded stop member 53 can be suitably rotated so as to axially adjust the position thereof, and hence locate the stop surface 54 at the desired axial location. When so located, as illustrated by FIG. 4, the stub end of a workpiece can hence be supported within the forward end of the collet while permitting accurate axial positioning of the workpiece. The washer 48 also provides additional support for the rearward end of the collet when the collet is radially compressed for gripping the workpiece, and this hence prevents undesired axially tipping of the blades 36 due to nonuniform radial compression of the collet. 
     Referring now to FIGS. 7 and 8, there is illustrated the workholder module 10 modified to form an expanding mandrel assembly 60. This mandrel assembly 60 includes therein the workholder module 10, and additionally mounts thereon an actuator 62 and a mandrel unit 63. 
     The mandrel unit 63 includes a substantially cylindrical mandrel 64 which is provided with a surrounding annular wall 65 adapted for gripping engagement with the internal bore of a workpiece. The cylindrical mandrel 64 has a conical bore 66 extending coaxially therethrough, and a plurality of slits or slots 67 project radially outwardly from this bore 66 through the outer annular surface 65 so as to divide the mandrel into a plurality of arcuate segments 68. There are four such slits 67 in the preferred embodiment, said slits being uniformly spaced apart so that each of the four segments 68 is hence of a substantially 90° extent. 
     The individual segments 68 of the cylindrical mandrel are secured to the outer end of an axially extending arm 69, the latter having its inner or rearward end secured to the base wall 71 of a mounting member or end cap 72, the latter being an integral part of the mandrel unit 63. This mounting member 72 is of a substantially cup-shaped configuration in that it includes an annular rearwardly projecting flange 73 which is internally threaded so as to be threadably engageable with the threads 14 provided on the front end of the housing 11. The base wall 71 of this mounting member 72 extends substantially across the forward end of the housing but is provided with an opening 74 extending coaxially therethrough, which latter opening provides coaxial communication between the mandrel bore 66 and the interior of the workholder module. 
     Considering now the actuator 62, same includes a main base plate 76 which is of a substantially cylindrical construction in that it is axially slidably supported within the forward end of the housing bore 12 and is thus disposed so as to abut against the forward end 19 of the activating sleeve 15. The axial thickness of plate 76 is less than the axial spacing between the base wall 71 and the end face 19 when the activating sleeve 15 is in the retracted position illustrated by FIG. 7. A plate-type spring 79 is disposed between the base plate 76 and the base wall 71 so as to normally urge the actuator 62 axially rearwardly against the front face 19. 
     The base plate 76 of actuator 62 has a substantially cylindrical stem 77 projecting coaxially forwardly therefrom through the opening 74, which stem 77 at its forward end is provided with a conical wedge 78, the latter having a slope substantially corresponding to that of the opening 66 so that the wedge 78 can be slidably inserted into the conical opening 66 to effect radially outward resilient expansion of the mandrel 64 when gripping of a workpiece is desired. 
     To activate the expanding mandrel illustrated by FIG. 7, and assuming it is in the release position illustrated by FIG. 7, then the workpiece is initially positioned in surrounding relationship to the cylindrical mandrel 64. The activating tube 26 is then axially moved forwardly, causing the sleeve 15 to push the actuator 62 forwardly. Wedge 78 then coacts with the conical bore 66 to cause radially outward expansion of the cylindrical mandrel 64, and hence cause the surface 65 thereof to grippingly engage the surrounding wall of an internal bore or opening as formed in the workpiece. When release of the workpiece is desired, the tube 26 is moved axially rearwardly, and the spring 79 causes the actuator 62 to be axially retracted. 
     Referring now to FIGS. 9 and 10, there is illustrated a step-type chuck assembly 80 formed by mounting a closer or end member 81 and a step chuck unit 82 on the workholder module 10. 
     The closer member 81 is of a generally cup-shaped configuration and includes a base wall 83 which partially closes off the front end of the housing and has a forwardly projecting annular flange 84, whereby the cup-shaped configuration of the closer member defines a forwardly-directed recess 85, which recess has the rear thereof bounded by the base wall 83. Recess 85 is surrounded by an inner annular side wall 86 which is of a conical configuration, which conical configuration is converging as it projects axially inwardly or rearwardly. 
     The closer member 81 has a further annular flange 87 which is integral with and projects rearwardly from the base wall 83. This latter annular flange 87 is internally threaded at 88 so as to be threadably engageable with the threads 14 provided on the front end of the housing to hence fixedly secure the closer member to the housing. 
     As to the step chuck unit 82, it comprises a one-piece member having a substantially cylindrical chuck plate 91 which is adapted to be received within the recess 85 of the closer member. This chuck plate 91 has a shallow cylindrical recess 92 formed therein, which recess extends inwardly from the front axial face 94 of the chuck plate and terminates at a bottom wall 93. The recess is surrounded by a radially inwardly directed annular surface 95 which functions for grippingly engaging an exterior annular surface of a workpiece. 
     Chuck plate 91 has a substantially cylindrical support hub 96 of smaller diameter projecting coaxially rearwardly therefrom. This support hub 96 projects axially through the closer member and into the bore of the activating sleeve 15. The rearward axial end of the cylindrical hub 96 is externally threaded at 97, and this external thread 97 is threadably coupled to the threaded bore 21 provided at the rearward end of the activating sleeve 15 so as to fixedly connect the activating sleeve 15 and step chuck unit 82 together. The hub 96 has a large diameter bore 98 formed therein, and the latter in turn communicates with a smaller diameter bore 99 which extends coaxially through the chuck plate 91. 
     The chuck plate 91 is provided with a plurality of slits or slots 101 which project radially from the bore 99 through the outer periphery of the plate. The outer annular surface 102 of this plate is tapered so as to effectively define a conical surface, the angle of which substantially corresponds to that of the annular side wall 86 so as to wedgingly cooperate therewith. This wedging cooperation between the tapered surfaces 86 and 102, coupled with the provision of the slits 101, which slits defied the chuck plate into a plurality (four in the preferred embodiment) of arcuate segments 100, hence permits these segments 100 to be resiliently deformed radially inwardly toward one another as the chuck plate is pulled axially rearwardly into the recess 85, and hence this causes the annular surface 95 to be moved into secure gripping engagement with an exterior annular surface of a workpiece. 
     To permit precise axial positioning of the workpiece within the recess 92, the chuck plate 91 has a plurality, here three, of small openings 103 extending axially therethrough, said openings being disposed in uniformly spaced relationship around the central axis of the chuck plate. Each opening 103 loosely slidably accommodates therein a cylindrical stop pin 104, the latter having a threaded stub on the rearward end thereof which is fixedly secured within a threaded opening 105 formed in the closer member. This stop pin 104 has a diameter which is slightly less than the diameter of the opening 103 so as to not interfere with the radial movement of the segments 100. Further, the stop pin 104 defines a stop surface 106 on the forward end thereof, the latter being spaced forwardly from the rear surface 93 of the recess, whereby the stop surfaces 106 on the plurality of stop pins hence effectively define a plane for precisely positioning the rear surface of the workpiece. 
     The stop pins 104 not only function as a workpiece positioning structure, but they also function as drive pins in that they transmit the rotational drive from the housing 11 through the closure member 81 to the step chuck unit 82. 
     The use and operation of the step chuck 80 illustrated in FIGS. 9 and 10 is believed self evident from the description set forth above. 
     Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.