Abstract:
A workpiece ejector and a method for ejecting workpieces from a turning machine such as a lathe. The turning machine has at least one spindle for receiving workpieces therethrough and at least one chuck associated with the spindle for holding a workpiece during machining operations. In one embodiment, the ejector includes a piston mounted at a location outside the spindle and proximate the chuck, the piston having a first end adapted to engage the workpiece and being movable between a first position where the first end is located outside the spindle and a second position where the first end and at least a portion of the piston are within the spindle. An actuator is operative to move the piston from the first position toward the second position. The actuator may include a mechanical spring.

Description:
TECHNICAL FIELD 
   The present invention generally relates to turning machines, such as lathes. More specifically, the invention relates to devices for automatically ejecting workpieces from turning machines. 
   BACKGROUND 
   Various types of feed mechanisms exist in the machine tool industry to automate the loading and/or unloading of workpieces into and out of a turning machine. Turning machines such as conventional hollow-spindle lathes may include a motor-driven rotating spindle which has a collet chuck mechanism connected to one end thereof for gripping material to be machined. In initial workpiece machining, which may be termed primary machining operations, workpieces may be machined from raw bar stock that extends from within the spindle and is gripped by the collet mechanism. After the primary machining is completed, the machined workpiece may be cut from the bar stock. Thereafter, the collet mechanism may be opened and additional bar stock may be fed through the spindle so that a new portion of the stock material may be received in the collet chuck mechanism for machining. This cycle is repeated to form several machined workpieces from the bar stock supplied through the spindle. 
   In many instances, secondary machining operations may be performed on workpieces that have previously been machined using the primary machining operation described above. These secondary operations are required, for example, when a different tool is needed to perform additional machining. In such cases, the previously-machined workpieces may be individually placed in the collet mechanism for further machining. In these secondary machining operations, the machined workpiece is held by the collet mechanism. Once the desired machining is completed on the workpiece, the machined workpiece must be ejected from the collet mechanism. 
   In other applications, multi-spindle lathes may be used to manufacture a machined part. Primary machining operations may be performed on bar stock material extending from a first spindle, whereafter the workpiece may be transferred to a second spindle for secondary machining operations. Generally, bar stock material will not be located in the second spindle, and finished workpieces may therefore be ejected through the second spindle. 
   Various workpiece ejectors have been proposed for use in turning machines, such as conventional lathes used in secondary operations. Conventional workpiece ejectors may generally include an elongated ejector push rod that extends through the spindle of an otherwise conventional lathe. The ejector push rod may be attached to an external plate that is driven by fixed, external air actuators to move the push rod into engagement with a workpiece and thereby eject the workpiece from the collet mechanism. As a result of the inclusion of external actuators, the space required for installation of a lathe including such an ejector may be substantially greater. In addition, conventional ejectors of this type may be costly and complex. 
   Other workpiece ejectors, such as the type disclosed in U.S. Pat. No. 5,715,735, are located inside the spindle, occupying some of the space which would otherwise be available for workpieces, and thereby limiting the size of the workpiece that can be machined. An additional drawback of this type of spindle-contained ejector is that it may deposit the finished workpiece in an area generally in front of the chuck, on one of the lathe surfaces, such as a chip pan or the lathe bed. Once this limited area fills up, manual intervention may be required in order for the accumulated finished workpieces to be removed. 
   Still other workpiece ejectors may be designed such that the ejecting mechanism, such as a spring or a pneumatically actuated piston or drive rod, will be restrained by the closed chuck holding the workpiece. When the chuck begins to open, and before if has fully released the workpiece, the spring or pneumatic device will begin the ejection, thereby potentially damaging the surfaces of the workpiece, due to contact with the chuck jaws during ejection. Such movement of the workpiece before the chuck has fully released the workpiece may not be suitable when a fine surface finish is desired. 
   Improvements to unloading devices for turning machines are therefore desirable. 
   SUMMARY 
   A workpiece ejector for turning machines having at least one spindle for receiving workpieces therethrough and at least one chuck associated with the spindle for holding a workpiece during machining operations may include a piston having a first end adapted to engage the workpiece and having a first position and a second position. The piston may be adapted to be mounted outside the spindle and proximate the chuck such that the first end is located outside the spindle in the first position and the first end is located within the spindle in the second position. The ejector may include an actuator operative to move the piston from the first position toward said second position when triggered by contact between a release mechanism and the chuck. 
   In another embodiment, a combination of a workpiece ejector and a turning machine may include a spindle for receiving workpieces therethrough, a chuck associated with the spindle and adapted to hold a workpiece, and a piston adapted to be mounted to the turning machine outside the spindle and proximate the chuck. The piston may have a first end adapted to engage a workpiece and may be moved between a first position where the first end is outside the spindle and a second position where the first end is within the spindle. The apparatus may further include an actuator operative to move the piston from the first position toward the second position when triggered by contact between a release mechanism and the chuck. The release mechanism may engage the piston and maintain it in the first position against the bias of a spring until selectively actuated to release the piston for movement toward the second position. 
   In yet another embodiment, a method of ejecting a workpiece from a turning machine having at least one spindle for receiving material therethrough and at least one chuck associated with the spindle for holding a workpiece during machining operations may include releasing the workpiece from the chuck, moving a piston mounted at a location outside the spindle and proximate the chuck from a first position outside the spindle to engage the workpiece, and rapidly extending the piston to a second position within the spindle such that the workpiece travels through the spindle and is ejected therefrom. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above-mentioned features, as well as other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of illustrative embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a side view of a lathe including an exemplary workpiece ejector; 
       FIG. 2  is a perspective view of the workpiece ejector shown in  FIG. 1 ; 
       FIG. 3  is a cross-sectional elevation view of the lathe chuck, the workpiece held by the chuck and the workpiece ejector of  FIGS. 1-2  prior to starting the ejection process; 
       FIG. 4  is a cross-sectional elevation view, similar to  FIG. 3 , with the workpiece having been released by the chuck, and the workpiece ejector and turret having been moved to cause contact between the piston and the workpiece; 
       FIG. 5  is a cross-sectional elevation view, similar to  FIG. 4 , with a piston entering the spindle and a latch and release mechanism making contact with the chuck; 
       FIG. 5A  is an enlarged detail view of the encircled area of  FIG. 5 ; 
       FIG. 6  is a cross-sectional elevation view, similar to  FIG. 5 , at the moment immediately prior to release of the workpiece ejector piston, showing the sliding motion of the latch and release mechanism; 
       FIG. 6A  is an enlarged detail view of the encircled area of  FIG. 6 ; 
       FIG. 7  is a cross-sectional elevation view, similar to  FIG. 6 , showing ejection of the workpiece; 
       FIG. 8  is a cross-sectional elevation view, similar to  FIG. 7 , showing the piston in an offset position prior to resetting the rod to its locked position; and 
       FIG. 9  is a cross-sectional elevation view, similar to  FIG. 8  showing the workpiece ejector in its locked position. 
   

   DETAILED DESCRIPTION 
     FIG. 1  depicts a turning machine in the form of a conventional CNC lathe  50  including an exemplary workpiece ejector  10 . Lathe  50  includes a headstock assembly  54  with front and back ends  58 ,  56 , a spindle  40 , a chuck  44 , and a tool turret  150  mounted to a main slide for movement of the turret  150  in directions toward and away from the chuck  44 , as known in the art. Bar stock is fed through the back of spindle  40  to be received in the chuck  44  on an opposite side of headstock assembly  54 . The turret  150  includes a plurality of tool stations, each configured to receive a workpiece cutting and finishing tool. Turret  150  may be rotated and advanced along the main slide to engage a tool with the end of the bar stock or a workpiece  100  mounted in chuck  44 . Lathe  50  may further include a computer  52  for controlling operation of the lathe  50 , as known in the art. 
   In the embodiment shown, an exemplary workpiece ejector  10  is mounted to a tool station on the turret  150 , with a longitudinal axis thereof aligned with the longitudinal axis of the spindle  40 . The workpiece ejector  10  is mounted on the turret  150  via a mounting block  160  surrounding a housing  12  of the workpiece ejector  10 , the details of which will be described further below. While the workpiece ejector  10  is shown and described as being mounted to the turret  150  using mounting block  160 , it will be appreciated that workpiece ejector  10  may alternatively be mounted to other portions of the lathe  50 , and by structure other than the mounting block  160 . The ejector is positioned with a disk  20  of a piston  18  generally facing the first end  42  of the spindle  40 , chuck  44  and front end  58  of the headstock assembly  54 . 
   With reference to  FIGS. 2 and 3 , the workpiece ejector  10  of  FIG. 1  is generally a uniaxial device with components generally concentric to each other. The ejector includes a tubular cylindrical housing  12  containing a compression spring  36 , a disk-shaped coupling adapter  14 , a latch and release mechanism  16 , a piston rod  26 , and a workpiece engaging disk  20 . A groove  22  and a radial protrusion  24  adjacent the groove  22  define portions of the surface of the piston rod  26 . The groove  22  and radial protrusion  24  are shaped to work in conjunction with the latch and release mechanism  16  to hold the piston  18  in a first position associated with the compressed condition of the spring in the housing  12 . 
   With continued reference to  FIGS. 2 and 3 , the workpiece ejector housing  12  has a generally closed first end  17  containing an air vent aperture  19  through a first end face  21 , for air pressure relief. The housing  12  comprises a first portion  27  of generally constant diameter that starts at its first end face  21  and a flange  13 . Housing  12  includes a bore  23 , extending through its axial center, to allow passage of piston rod  26 , and first and second end faces  21 ,  25 . Air passages  15  extend generally radially outwardly from bore  23  of the housing  12  to the circumferential surface  30  of flange  13 . These passages  15  allow air to pass between the central bore  23  and the exterior of the housing  12  as piston rod  26  reciprocates within bore  23 . 
   With continued reference to  FIGS. 2-3 , a coupling adapter  14  is coupled to the housing  12  by conventional fasteners, such as bolts  11 . Coupling adapter  14  generally has an outer diameter identical to that of flange  13  of the housing  12 , has a bore  28  sized to allow passage of the piston rod  26 , and provides a mounting surface for latch and release mechanism  16 , thereby coupling latch and release mechanism  16  to housing  12 . The adapter  14  has first and second flat, parallel, end faces  31 ,  33 . The first face  31  abuts the second end face  25  of the housing  12  and, as indicated above, is affixed to housing  12  by conventional bolts  11 . Even though the adapter  14  in this embodiment is of a diameter substantially equal to that of flange  13  of housing  12 , persons skilled in the art will appreciate that other relative dimensions may alternatively be suitable for adapter  14 . During operation, adapter  14  limits the travel of the compression spring  36  when actuated. 
     FIG. 3  shows an o-ring  32  made of a resilient, high-impact material such as a rubber-based composite, located in the central bore  23  of the housing  12 , and positioned between the sleeve  51  and the first face  31  of the coupling adapter  14 . The o-ring  32  acts as a bump stop, preventing direct contact between the piston  18  and the adapter  14 , thereby minimizing the probability of impact damage from contact between the sleeve  51  or spring  36  and the coupling adapter  14 . While an o-ring is shown and described, other suitable elements may be substituted for the o-ring  32  to prevent damage to the piston  18 , sleeve  51 , spring  36  and adapter  14 . 
     FIG. 3  shows a compression spring  36  in the central bore  23  of the housing  12 . The outer diameter of the spring  36  is sized to fit closely within the inner diameter of the bore  23  of the housing  12 , to prevent buckling of the spring  36  during compression and lateral travel during extension thereof. 
     FIGS. 2-3  also show a piston  18  having a generally cylindrical piston rod  26  with first and second ends  35 ,  37 . The first end  35  of the rod  26  is adjacent a first end  38  of the spring  36  and may or may not be affixed thereto. Affixation may be accomplished by any suitable method or structure, such as adhesive, mechanical bonding, welding, magnetic coupling devices or any combination thereof. Piston rod  26  may alternatively be integrally formed with the spring  36 . Ejector  10  further includes a sleeve  51  operatively coupled to the piston rod  26 , adjacent the first end  35 , for contacting the spring  36  and maintaining the piston rod  26  centered within bore  23  as piston  18  reciprocates in bore  23 . 
   The second end  39  of the spring  36  is adjacent the interior of the first end  17  of the housing  12  and may or may not be affixed thereto. Affixation may be accomplished by any suitable method or structure, such as those recited above for attachment of the first end  38  of the spring  36  to the piston rod  26 . Alternatively, the second end  39  of the spring  36  may be left unaffixed to the housing  12 . 
   With continued reference to  FIGS. 2-3 , the second end  37  of the piston rod  26  is coupled to a metal disk  20  by any suitable method, such as by a conventional screw  41  extending through the center of the disk  20  and rod  26 . Other alternatives such as integrally forming the disk  20  to rod  26  or other methods or structure for interconnecting these two elements may be substituted. Such methods may include, for example, those involving mechanical bonding, adhesives, welding or the use of a different type and/or number of fasteners suitable to hold the rod  26  and disk  20  together. 
   Ejector  10  includes a generally tubular latch and release mechanism  16  slidably disposed over the piston rod  26 , and adjacent the second face  33  of the coupling adapter  14 . The release mechanism  16  includes concentric first and second collars  43 ,  45  slidably disposed over the piston rod  26 . Second collar  45  is slidably and partially mounted over the first collar  43  and has a first end  47  generally facing the coupling adapter  14  and a second, opposite end  48 . Latch and release mechanism further  16  includes a conventional, spring-biased, quick-release mechanism having a spring  49  that urges first collar  43  in a direction toward disk  20  so that roller bearings  55  are retained in a position that engages groove  22  and the annular protrusion  24  on piston rod  26  to thereby lock the piston rod  26  in the first, retracted position. As first collar  43  is moved in a direction away from disk  20 , the bearings  55  are released for movement to disengage from groove  22  and protrusion  24  to thereby permit piston rod  26 , biased by spring  36 , to move rapidly toward the second, extended position (see  FIG. 7 ). 
   While the latch and release mechanism  16  has been described in detail as including concentric collars and a quick-release mechanism, persons skilled in the art will appreciate the fact that various other types of latch and release mechanisms can be alternatively adapted to work in conjunction with the workpiece ejector  10 . For example, a hydraulically operated mechanism may be provided and may be configured to utilize the high pressure cooling fluid supplied to the turret  150  to selectively latch and release the piston rod  26  under the control of computer  52 . Alternatively, a pneumatically operated mechanism may be provided, or various other mechanisms may be used to selectively latch and release the piston rod  26 . These other types of latch and release devices may be useful when the configuration of a workpiece does not facilitate engaging latch and release mechanism  16  with chuck  44 , as described below. 
     FIGS. 3-9  show a workpiece  10  and a conventional collet chuck  44  for holding a workpiece  100  during operation of a turning machine, such as a lathe. When the chuck  44  is open, the workpiece  100  is released to be moved or removed. Upon completion of processing of the workpiece  100  being held by the chuck  44 , the chuck  44  is opened as indicated by the vertical arrows  62   a ,  62   b  ( FIG. 3 ) to allow free movement of the workpiece  100  within, into or out of the lathe spindle  40 . The turret  150  on which the workpiece ejector  10  is mounted is rotated and oriented such that the longitudinal axis of ejector  10  is substantially aligned with the axis of the spindle  40 . The turret  150  may also be translationally moved in the direction of the spindle  40  and workpiece  100 , as indicated by the horizontal arrow  64  ( FIG. 3 ). 
   As shown in  FIG. 4 , the translational motion of the turret  150  causes contact to occur between the piston disk  20  and the end face  110  of the workpiece  100  to push the workpiece  100  into the headstock assembly  54 . The turret  150  and ejector  10  are advanced toward spindle  40  so that the second end  48  of the second collar  45  of the latch and release mechanism  16  makes contact with the outer flat surface  66  of the chuck  44 , as depicted in  FIGS. 5-5A . At this point, the piston  18  is partially in the spindle  40 , maintaining contact with the end face  110  of the workpiece  100 . 
   With reference to  FIGS. 6-6A , as turret  150  and ejector  10  continue moving toward spindle  40 , the first and second collars  43 ,  45  of the latch and release mechanism  16  are moved in a direction to compress spring  49  and thereby cause the bearings  55  to disengage from groove  22  and protrusion  24 , thereby permitting piston  18  to freely and rapidly move toward the piston&#39;s extended position by action of the force exerted by the ejector spring  36 . At this point in the ejection cycle, the piston disk  20  remains in contact with the workpiece  100  inside the spindle  40 . 
   With reference to  FIG. 7 , a point in the ejection cycle is shown whereby the bearings  55  in the latch and release mechanism  16  have been disengaged from the groove  22  of the piston rod  26 , allowing the ejector spring  36  to move the piston  18  toward the extended position, consequently causing the disk  20  of the piston  18  to push the workpiece  100  through the spindle  40 . In one embodiment, the ejector  10  is designed such that the force of spring  36  will be sufficient to push the workpiece  100  completely through the spindle  40  and cause it to exit the spindle  40  from the tubular protrusion  46  of the spindle  40  proximate the back end  56  of the headstock assembly  54 . 
   With reference to  FIG. 8 , the workpiece  100  is shown having been ejected from the spindle  40  and the turret  150  having been moved away from the headstock assembly  54  a distance sufficient for the piston  18  to be completely withdrawn from the spindle  40  and chuck  44 . A rotatable portion of the turret  150  is then rotated to a position where the piston disk  20  can be projected to make contact with the outer surface  66  of the chuck  44 . The turret  150  is then moved in the direction of the chuck  44  and headstock assembly  54 , causing the chuck  44  contacting the disk  20  to push the piston  18  inwardly toward the first position, thereby compressing the spring  36 . 
   With reference to  FIG. 9 , the piston  18  has been pushed against the chuck  44  to a point where the locking bearings  55  of the latch and release mechanism  16  have engaged the groove  22  in the piston rod  26 , locking the piston  18  in a position associated with the compressed condition of the ejector spring  36 . Upon reaching this locked state, the forward motion of the turret  150  is ceased and the turret  150  is translationally retracted back to its starting position away from the chuck  44 . The operator may now proceed to load a new workpiece  100  into the spindle  40  of the lathe  50 . 
   The method and apparatus described above avoids damage to the surface of the workpiece  100 . This is so because the workpiece  100  is pushed and eventually ejected by the piston  18  while the chuck  44  is in its open condition. This prevents damage that may be otherwise observed with other ejection systems that use the frictional force of the chuck jaws  60  to act against the driving force of a spring, pneumatic or other actuation system actuating an ejector. In such systems, damage to a workpiece may occur because such ejectors begin to push the workpiece before the chuck jaws  60  have fully released the workpiece, thereby causing scratching of the workpiece surface. 
   While operation of the workpiece ejector  10  has been described above to include moving the piston rod  26  partially inside the spindle  40 , engaging the release mechanism with the chuck  44 , and pushing the piston rod  26  against the chuck  44  to reset the piston  18 , it will be recognized that the workpiece ejector may alternatively be operated in various other ways. For example, the configuration of a workpiece  100  may be such that the piston rod  26  does not extend within the spindle  40  when the turret is moved to initially engage the workpiece, as described above. Instead, the piston rod  26  may still be located outside the spindle  40  after the piston rod has begun to push the workpiece through the spindle. In such applications, it may be desired to actuate the piston rod  26  to eject the workpiece using other mechanisms, such as hydraulic mechanisms, pneumatic mechanisms, or various other devices. It will also be recognized that the piston rod  26  need not be reset only by pushing the piston rod  26  against the chuck  44 . The piston rod  26  may alternatively be reset by pushing the piston rod  26  against other structure of the lathe  50 , or by using hydraulic mechanisms, pneumatic mechanism, or various other devices suitable for moving the piston rod  26  from the extending position to the retracted position. 
   A receptacle or bin  120  may be placed proximate the second end  46  of the spindle  40  to receive ejected workpieces. The dimensions and shape of the bin may depend on factors such as the rate of production of finished workpieces and associated storage/holding requirements. Other factors may also include, for example, the amount of available space in the area immediately proximate the second end  46  of the spindle  40 , as well as the required structural rigidity of the bin  120  to withstand the weight and impact of workpieces falling into it. 
   While the ejector  10  shown and described herein includes a spring to rapidly move piston rod  26  toward the extended position, it will be appreciated that various other methods or components may be substituted, such as those including, for example, pneumatic, magnetic, electric, hydraulic, combustion or solid-propellant components or methods. 
   Yet another embodiment of the present invention may involve, for example, a tension spring rather than the compression spring  36  of the workpiece ejector  10  of  FIGS. 1-9 . In such case, the starting, locked position of the piston  18  would be associated with the stretched condition of the tension spring while the released position would be associated with the relaxed condition of the tension spring. 
   While the invention has been described with specific examples in reference to specific embodiments, persons skilled in the art will appreciate that various modifications and changes may be made to the invention as described herein without departing from the spirit and scope thereof which are defined by the appended claims.