Loading system and collect assembly for grinding a workpiece

Information

  • Patent Grant
  • 6193591
  • Patent Number
    6,193,591
  • Date Filed
    Wednesday, November 24, 1999
    25 years ago
  • Date Issued
    Tuesday, February 27, 2001
    23 years ago
Abstract
An assembly for holding a cylindrical workpiece for grinding, including a support frame having at least one support arm extending to initially hold the workpiece and operable to disengage from the workpiece during grinding, a tailstock slidably mounted on the support frame and operable to engage the proximal end of the workpiece, and a collet assembly mounted on the support frame and configured to receive and engage the distal end of the workpiece. The collet assembly includes a housing having an open proximal end, an open distal end, and an internal channel with an inner diameter. The internal channel extends along the length of the housing from the open proximal end to the open distal end and is adapted to slidingly receive a spindle. The spindle has a proximal end portion and a distal end portion. The proximal end portion includes a holding portion and the distal end extends from the distal end of the housing and is engagable with a drive mechanism. The collet is slidably disposed within the proximal end portion of the housing. The distal end of the collet is attached to the holding portion of the spindle. The collet is resiliently biased so that the collet opens when advanced in the proximal direction, and so that the proximal portion of the housing urges the collet to close when the collet is retracted in the distal direction. The assembly further includes means engagable with the spindle for selectively advancing the spindle within the housing to advance the collet. A spring is disposed between the housing and the spindle and biased to resiliently urge said spindle in the distal direction.
Description




FIELD OF THE INVENTION




This invention relates generally to grinding machines and more particularly to a system and collet assembly for loading, holding, turning and ejecting a workpiece.




BACKGROUND OF THE INVENTION




In grinding cylindrical workpieces, such as rollers, it is desirable to make consistent end products from the rough workpieces as efficiently as possible. Aside from the actual grinding time, improvements are needed to minimize the time necessary to load, clasp, rotate, move and eject the workpieces. Although in some cases the process has been automated, it is still desirable to improve machining efficiency and cycle time. One area in which time and efficiency are lost is in engaging and disengaging the workpiece by the grinding machine. In particular, many grinding machines use a collet or cylindrical, slotted clamp to engage one end of the workpiece, whereafter the collet is rotated to rotate the workpiece. Engineering difficulties have been encountered in configuring the collet to engage the workpiece quickly, allowing the collet to rotate, and disengaging the collet from the workpiece.




One response to this challenge has been to mount an outwardly biased collet within a cylindrical sleeve which is clamped in place, such as described in U.S. Pat. Nos. 5,443,411 and 5,556,326, both to Rouyer et al. and incorporated herein in their entirety. The collet is both rotated and extended to allow it to expand and then retracted with a rotation and translation motion to close and lock it relative to the sleeve. Specifically, the collet receives the end of the workpiece when the collet is in the extended open position. The collet is then turned and retracted into clamped sleeve, closing the collet untiocollet firmly clasps the workpiece and abuts the sleeve. The clamp on the sleeve is then released and the sleeve and collet are jointly rotated to turn the workpiece for grinding. After grinding, the sleeve is again clamped and the collet turned and extended to release the workpiece. This approach requires an excessive number of working parts and steps, and adds complexity, wear and tear, and processing time to the system.




Consequently, there is a need for an improved method of loading, clamping, and releasing a workpiece for grinding. The present invention addresses these needs.




SUMMARY OF THE INVENTION




The present invention relates to an assembly for holding a cylindrical workpiece for grinding. Normally the workpiece has a proximal end and a distal end. The assembly is based on a support frame having at least one support arm extending to initially hold the workpiece and operable to disengage from the workpiece during grinding. A tailstock is slidably mounted on the support frame and operable to engage the proximal end of the workpiece.




In one preferred embodiment, a collet assembly is mounted on the support frame and configured to receive and engage the distal end of the workpiece. The collet assembly includes a housing having an open proximal end, an open distal end, and an internal channel. The internal channel extends the length of the housing from the open proximal end to the open distal end. A spindle is slidably disposed within the internal channel of the housing. The spindle has a proximal end portion and a distal end portion wherein the proximal end portion includes a holding portion and wherein the distal end extends from the distal end of the housing and is engagable with a drive mechanism.




A collet is slidably disposed within the proximal end portion of the housing, wherein the collet has a proximal end adjacent the proximal end portion of the housing. The distal end of the collet is engaged by the holding portion of the spindle. The collet is resiliently biased so that the collet opens when advanced in the proximal direction, and so that the proximal portion of the housing urges the collet to close when the collet is retracted in the distal direction.




The assembly includes means engagable with the spindle for selectively advancing the spindle within the housing to advance the collet. A spring is disposed between the housing and the spindle and biased to resiliently urge said spindle in the distal direction.




It is one object of the invention to provide an improved collet assembly and system for loading, clamping, rotate and ejecting a workpiece.




Further objects, features and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a perspective view of a system according to one embodiment of the present invention.





FIG. 2

is a side, partially cut-away view of a collet assembly according to one embodiment of the present invention.





FIG. 3

is a side view of a housing assembly with a spindle and collet according to the embodiment of the present invention illustrated in FIG.


2


.





FIG. 4

is a perspective view of a collet used in accordance with the embodiment of the invention illustrated in

FIGS. 2 and 3

.





FIGS. 5A and 5B

are side and top views, including interior lining, of a spindle used in accordance with the embodiment of the invention illustrated in

FIGS. 2 and 3

.





FIGS. 6A and 6B

are side, partially cut-away view and a top view of a housing used in accordance with the embodiment of the invention illustrated in

FIGS. 2 and 3

.





FIGS. 7A and 7B

are side and top views of a ring used in accordance with the embodiment of the invention illustrated in

FIGS. 2 and 3

.





FIGS. 8 and 9

are side, cut-away views of bracket plates used in accordance with the embodiment of the invention illustrated in

FIGS. 2 and 3

.





FIG. 10

is an enlarged cut-away view of a first embodiment of the tailstock of FIG.


1


.





FIG. 11

is side view of a clamp used in an alternate embodiment of the tailstock of FIG.


1


.











DESCRIPTION OF PREFERRED EMBODIMENTS




For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations, modifications, and further applications of the principles of the invention being contemplated as would normally occur to one skilled in the art to which the invention relates.




The present invention provides an improved loading system and collet assembly for grinding a workpiece. One example of such a workpiece is a paper handling roller with a metal bar core having a rubber sheath formed around it, wherein the rubber sheath needs to be sized. In operation, once a workpiece is loaded onto the support arms, the tailstock engages one end of the workpiece, pushing the opposing end into the collet assembly. The collet then clamps an end of the workpiece and is rotated. The workpiece is then translated into position for grinding and is ground until a desired workpiece diameter is achieved. The workpiece translation is then reversed and the workpiece is ejected from the system. The present invention provides reduced complexity and improved speed in processing each workpiece.





FIG. 1

illustrates a perspective view of one embodiment of a loading system


10


. Loading system


10


is mounted on frame


11


. A workpiece


12


having a proximal end


13


and a distal end


14


is loaded onto support arm(s)


17


. Preferably, there are at least two support arms


17


operationally coupled to cover


15


such that the support arms may be positioned to accept workpieces


12


of varying lengths. Support arms


17


may be hooked, notched, or otherwise adapted to receive and hold a workpiece


12


. In alternate embodiments, support arms


17


can be placed at various support positions on workpiece


12


.




Once workpiece


12


loaded in place, tailstock


20


advances the line with workpiece


12


until tailstock


20


engages proximal end


13


of workpiece


12


. Tailstock


20


then advances workpiece


12


until distal end


14


enters collet assembly


30


. Once workpiece


12


is in place, collet assembly


30


is activated to clamp distal end


14


and support arms


17


are withdrawn. Portions of collet assembly


30


are then rotated, imparting a rotation to workpiece


12


. Loading system


10


then laterally advances toward grinder


26


and rotating workpiece


12


is presented to grinder


26


. Grinder


26


is preferably a grinding wheel or drum, and is more preferably covered by a protective canopy


27


, which is automatically raised as workpiece


12


is moved to engage grinder


26


. Grinder


26


rotates in a direction opposite the rotation of workpiece


12


, thus grinding workpiece


12


until the desired diameter is reached. A biasing center support (not shown) may optionally be used to bias the center of the workpiece


12


to prevent bowing. Loading system


10


then translates laterally in a reverse direction to withdraw workpiece


12


from grinder


26


, and collet assembly


30


unclamps and ejects workpiece


12


. Preferably, these operations are directed by an electronic controller (not shown), but may be directed mechanically or manually as desired.





FIGS. 2-9

illustrate collet assembly


30


and various component parts. Collet assembly


30


is shown in detail in FIG.


2


. Collet assembly


30


includes generally cylindrically shaped housing


31


(shown in detail in

FIGS. 3

,


6


A, and


6


B) with internal channel


32


defining an inter channel diameter. Housing


31


has a housing proximal end


33


oriented generally toward the expected workpiece and an opposite housing distal end


34


. Spindle


40


(illustrated in detail in

FIGS. 3

,


5


A, and


5


B) is slidably disposed within internal channel


32


of housing


31


. Spindle


40


has spindle proximal end


47


, which ends in holding portion


38


, oriented toward housing proximal end


33


. Spindle distal end


48


extends beyond housing


31


and is adapted to be engaged by a rotation drive (not shown). Collet


44


is mounted in internal channel


32


adjacent housing proximal end


33


. Collet


44


includes collet distal end


46


attached to holding portion


38


of spindle


40


. Ring


35


encircles a distal portion


43


of spindle


40


outside and adjacent to housing


31


and is disposed between housing


31


and a washer


36


held on spindle


40


by nut


37


.




Outside of housing


31


is a reciprocating member, such as ring


55


, which is connected through housing


31


to spindle


40


by pin


58


. Ring


55


, spindle


40


and housing


31


have overlappingly aligned retaining pin holes for pin


58


. Displacement member


52


is adjacent housing


31


and abuts ring


55


. Air piston


50


is situated to selectively engage displacement member


52


, including tab


53


. Collet


44


is selectively held open by the activation of air piston


50


which moves sliding ring


55


, pin


58


, spindle


40


and collet


44


forward. First, second, and third base plates


70


,


72


and


74


hold rotation assembly


80


in place horizontally and vertically, but allow the assembly to rotate with various bearings


76


. Connectors


78


such as nuts and bolts are used to hold the base plates together.




In one embodiment, pin


58


is smooth or roughened and held in place by a frictional fit with ring


55


and/or spindle


40


. In alternate embodiments, pin


58


is a threaded pin, a set screw or a bolt. Pin


58


can extend the entire diameter of ring


55


or only into spindle


40


. Alternately, two pins can be used. Pin


58


can also be a member soldered, welded or otherwise solidly connected in place to hold a fixed relationship between ring


55


and/or spindle


40


.




Rotating assembly


80


is illustrated in

FIG. 3

including housing


31


, spindle


40


, ring


55


, pin


58


and collet


44


. When driven, rotating assembly


80


rotates in place as held by the base plates and bearings. In one embodiment, spindle


40


and housing


31


are nested, generally cylindrical shapes.




Collet


44


, enlarged in detail in

FIG. 4

, includes a plurality of clamping prongs


45


and distal connecting portion


46


. Collet


44


preferably has either


3


or


4


prongs


45


, although more or fewer prongs


45


may be used as desired. Collet


44


is outwardly biased such that prongs


45


are open when collet


44


is tended, and prongs


45


are forced to close when collet


44


is retracted into the proximal end of housing


3




1


. In one embodiment distal connecting portion


46


is threaded.




Side and top views of spindle


40


are shown in FIGS.


5


A and SB. In one embodiment, spindle


40


includes ho ldi ng portion


38


which engages distal p ortion


46


of collet


44


. In one embodiment, holding portion


38


threadedly engages distal portion


46


. Holding portion


38


may engage distal portion


46


by any convenient means, including, and not by means of limitation, snaps, a retaining member, a fiiction fit, solid connection, or the like. Spindle


40


includes retainig pin hole


39


.





FIGS. 6A and 6B

illustrate side and top views of housing


3




1


, respectively. Housing


31


includes stop ring or flange(s)


42


which abut bearings in base plate


70


to prevent housing


31


from sliding forward during use. Housing


31


includes elongated retaining pinhole


41


which is aligned with retaining pin hole


39


in spindle


40


. A reciprocating member, such as ring


55


, illustrated in

FIGS. 7A and 7B

, is positioned around housing


31


(as shown in FIG.


3


), with retaining pin hole


56


aligned with elongate housing retaining pin hole


41


and spindle retaining pin hole


39


. Pin


58


is positioned through retaining pin holes


56


,


41


and


39


such that when ring


55


is reciprocally moved along housing


31


, there is sufficient room in elongate pin hole


41


to transmit the sliding motion to spindle


40


via pin


58


, without slidably moving housing


31


. Thus, reciprocal sliding movement of ring


55


extends and retracts collet


44


from the proximal end of housing


31


. When spindle


40


is rotated, rotation assembly


80


which includes housing


31


, ring


55


, pin


58


and collet


44


are rotated as well. To enhance the spread of collet


44


upon extension, proximal end


59


of internal channel


32


of housing


31


can be flared.





FIGS. 8 and 9

illustrate in greater detail the base plates and mounting brackets shown in FIG.


2


.

FIG. 8

is a cut-away view of first base plate


70


, while

FIG. 9

is a cut-away view of third base plate


74


. Base plates


70


,


72


and


74


are aligned and mounted to the frame and serve to prevent rotation assembly


80


from moving from a desired position while allowing rotation assembly


80


to rotate. The base plates include appropriate flanges, channels and tabs to hold rotation assembly


80


.





FIG. 10

shows one embodiment of tailstock


20


.

FIG. 10

illustrates a first embodiment of tailstock


20


, having a tailstock housing


98


within which a pin


100


is recessed. Pin


100


is biased outwardly by spring


102


and may extend through a generally cylindrical housing recess


103


. Bearing


104


is disposed within cylindrical housing recess


103


and is adapted to engage the proximal end of a workpiece


12


.




In operation, workpiece


12


is loaded into system


10


and proximal end


13


is engaged by the pin


100


of tailstock


20


. As tailstock


20


moves to further engage proximal end


13


, proximal end


13


extends into housing recess


103


and is engaged by bearing


104


. When proximal end


13


has traveled far enough into housing recess


103


to be completely engaged by bearing


104


, pin


100


is recessed into housing


104


and sensor


106


sends a signal to a controller (not shown).





FIG. 11

illustrates a vertical clamp


110


which can be used instead of bearing


104


in an alternate embodiment of tailstock


20


. Clamp


110


, located proximate the opening to housing recess


103


, is adapted to engage workpiece


12


. In operation, workpiece


12


is loaded into collet assembly


30


and proximal end


13


is engaged by the clamp


110


. After engagement of proximal end


13


, the alternate embodiment operates substantially the same as tailstock


20


.




When system


10


is used, a workpiece


12


is loaded onto support arms


17


. Tailstock


20


is then advanced toward workpiece


12


until it engages proximal end


13


. Workpiece


12


and tailstock


20


are moved until distal end


14


is within open collet


44


extended from air collet assembly


30


. Collet


44


is selectively held open by the activation of air piston


50


which moves sliding ring


55


, pin


58


, spindle


40


and collet


44


forward. Once distal end


14


of workpiece


12


is within collet


44


, air piston


50


is disengaged, where in spring


34


slidably retracts spindle


40


such that proximal end


33


of housing


31


forces collet


44


closed and locks it upon distal end


14


of workpiece


12


. A rotation is then imparted to rotation assembly


80


to rotate workpiece


12


. System


10


is advanced toward grinder


26


and held in place until a predetermined diameter of workpiece


12


is obtained. Upon the completion of grinding, the movement is reversed and air piston


50


is activated to eject workpiece


12


. The next workpiece


12


may then be loaded onto system


10


and the steps repeated.




Appropriate bearings, bushings, spacers, placement tabs and connectors are used to hold the assembly together as will be understood by those of skill in the art. Air piston


50


is illustrated as one movement means for pushing displacement member


52


. It will be understood that alternate hydraulic, pneumatic or mechanical means could be used as well.




For purposes of illustration, one embodiment of the air collet assembly has a length of 229 millimeters and a height of 85 mm. The housing has a diameter of 25.4 mm with the internal channel having a diameter of 15.1 mm until it reaches an interior shoulder at the proximal portion wherein the diameter is reduced to 13.5 mm. A 20 degree flare is imparted to the last 6.4 mm of the proximal end of the housing. In this embodiment the spindle has a standard diameter of 15.0 mm and a length of 210 mm prior to extended to the drive means. Retaining pin hole


39


has a diameter of 5.1 mm. Retaining pin hole


41


has a elliptical length of 5 mm between the foci plus a radius of 2.6 mm on each end. Retaining pin hole


56


has a diameter of 5 mm. These measurements are for illustration purposes only and are not intended to be limiting to the invention.




As will be understood by those of skill in the art appropriate materials may be used to construct the system and assembly including steel, rubber, and appropriate engagement surfaces having sufficient strength to engage and hold the workpiece during grinding and movement. As will be further understood by those skilled in the art, various motors, mechanical actuators, controllers, and sensors may be appropriately stationed to actuate and control the various mechanical and feedback operations of the system.




While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.



Claims
  • 1. An assembly to hold the proximal and distal ends of a workpiece for grinding, comprising:a support frame; a tailstock slidably mounted on said support frame and operable to engage the proximal end of the workpiece; and, a collet assembly mounted on said support frame and configured to receive and engage the distal end of the workpiece, wherein said collet assembly includes: a housing defining an open proximal end, defining an open distal end, and defining an internal channel extending along the length of said housing from said proximal end to said distal end; a spindle slidably disposed within said internal channel of said housing, said spindle having a proximal end and a distal end wherein said proximal end includes a holding portion and wherein said distal end extends from said distal end of said housing and is engagable with a drive mechanism; a collet disposed within said internal channel of said housing and connected to said holding portion, wherein said collet has a proximal end adjacent said housing proximal end, wherein said collet is resiliently biased such that said collet opens when advanced in the proximal direction and wherein said housing proximal end urges said collet closed when said collet is moved in the distal direction; and, means selectively engagable with said spindle for slidably advancing and retracting said spindle to advance and retract said collet.
  • 2. The assembly of claim 1 wherein said means forslidably advancing and retracting includes a spring disposed between said housing and said spindle and biased to resiliently urge said spindle in the distal direction.
  • 3. The assembly of claim 2 wherein said means forslidably advancing and retracting includes a reciprocal member slidably mounted externally to said housing and in a fixed position relative to said spindle.
  • 4. The assembly of claim 3 wherein said collet assembly and said reciprocal member are rotatably mounted to said support frame.
  • 5. The assembly of claim 4 wherein said reciprocal member is a ring.
  • 6. The assembly of claim 4 wherein said means for slidably advancing and retracting includes an air piston adapted to selectively advance said reciprocal member in the proximal direction.
  • 7. The assembly of claim 6 wherein said collet includes a plurality of clamping prongs adapted to open when said collet is extended from said housing proximal end and are further adapted to close when said collet is retracted into said open housing proximal end portion.
  • 8. The assembly of claim 7 wherein said plurality of clamping prongs is 3.
  • 9. The assembly of claim 3 wherein said collet includes a threaded distal end portion and wherein said holding portion is threaded such that said collet distal end portion engages said holding portion.
  • 10. A rotatable collet assembly for holding an end of a workpiece, comprising:a housing defining an open housing proximal end, an open housing distal end, defining an internal channel extending from said open housing proximal end to said open housing distal end and defining a first retaining pin hole; a spindle having a spindle proximal end and a spindle distal end, slidably disposed within said internal channel, wherein said spindle proximal end includes a holding portion, wherein said spindle distal end extends from said housing distal end and is engagable with a drive mechanism, and wherein said spindle defines a second retaining pin hole in overlapping aligmnent with said first retaining pin hole; a collet disposed within said internal channel of said housing and connected to said holding portion, wherein said collet has a proximal end adjacent said housing proximal end, wherein said collet is resiliently biased such that said collet opens when advanced in the proximal direction and wherein said housing proximal portion urges said collet to close when said collet is moved in the distal direction; a reciprocating member mounted externally to said housing and defining a third retaining pin hole in overlapping alignment with said first and second retaining pin holes; a pin mounted through said first, second and third retaining pin holes wherein said pin engages said second and third retaining pin holes and wherein said first retaining pin hole allows said pin to reciprocally travel in the proximal and distal direction in relation to said housing when said reciprocating member is moved; and, a spring disposed been said housing and said spindle asked to resiliently urge said spindle in the distal direction.
  • 11. The collet assembly of claim 10 wherein said reciprocating member is a ring.
  • 12. The collet assembly of claim 11 further comprising a displacement member engagable with said ring.
  • 13. The collet assembly of claim 12 further comprising an air piston associated with said displacement member, wherein said air piston is engagable to selectively advance said displacement member in a proximal direction.
  • 14. The collet assembly of claim 13 wherein said collet includes a plurality of clamping prongs adapted to open when said collet is extended from said housing proximal end and adapted to close when said collet is retracted into said open housing proximal end portion.
  • 15. The collet assembly of claim 14 wherein said plurality of clamping prongs is 3.
  • 16. The assembly of claim 13 wherein said collet includes an threaded distal end portion and wherein said holding portion is threaded such that said collet distal end portion engages said holding portion.
  • 17. A rotatable collet assembly for holding an end of a workpiece comprising:a housing defining an open housing proximal end, defining an open housing distal end and defining an internal channel extending from said open housing proximal end to said open housing distal end; a collet slidably disposed within said internal channel, wherein said collet has a proximal end portion adjacent said housing proximal end, wherein said collet is resiliently biased such that said collet opens when advanced in a proximal direction and wherein said housing proximal end urges said collet closed when said collet is moved in a distal direction; means associated with said collet to selectively advance said collet in relation to said housing; a spring associated with said housing and said collet and biased to resiliently urge said collet in the distal direction.
  • 18. The assembly of claim 17 further comprising a spindle slidably disposed within said internal channel, said spindle having a spindle proximal end and a spindle distal end, wherein said spindle proximal end is attached to said collet, and wherein said spindle distal end extends from said housing distal end and is engagable with a drive mechanism.
  • 19. A method of holding a cylindrical workpiece for grinding wherein said workpiece has a proximal end and a distal end, comprising the steps of:providing a support frame; engaging the proximal end of the workpiece with a tailstock mounted to said support frame; advancing a collet from a collet assembly wherein said collet assembly includes: a housing having an open proximal end; a collet rectally disposed within said housing, wherein said collet is disposed within said proximal end of said housing such that said collet is resiliently biased to open when advanced in the proximal direction and wherein said proximal end urges said collet closed when said collet is retracted; and, advancement means for selectively slidably advancing said collet proximally from said housing; receiving the distal end of the workpiece within said collet; retracting said collet to engage the distal end of the workpiece wherein said retraction is accomplished by a spring associated with said housing and said collet and resiliently biased to move said collet in a distal direction; advancing said collet to disengage the workpiece after grinding; and ejecting the workpiece.
  • 20. The method of claim 19 wherein said collet assembly offer comprises a spindle slidably disposed within said housing wherein said spindle has a proximal end coupled to said collet and wherein said spindle has a distal end attachable to a driving mechanism.
US Referenced Citations (4)
Number Name Date Kind
5312212 Naumec May 1994
5375458 Oliver et al. Dec 1994
5806859 Saccomanno, III Sep 1998
5947485 Nguyen Sep 1999