EXPANDABLE ARBOR, CLAMPING SYSTEM AND METHOD OF CLAMPING ONE OF A WORKPIECE AND A TOOL TO A MACHINE

An expandable arbor for rotatably mounting an object to a machine tool comprises a mounting portion fastenable to a machine tool spindle and a clamping portion located on the mounting portion. The clamping portion comprises a finger extending from the mounting portion, an expandable sleeve coupled to the finger, and a nut for coupling the expandable sleeve to the mounting portion and for coupling the mounting portion to the rotating spindle. The expansion of the expandable sleeve allows for the clamping of the expandable sleeve to an internal surface of a tool or workpiece.

DETAILED DESCRIPTION

As shown inFIG. 1, an expanding arbor for rotatably clamping a workpiece or tool to a machine tool is designated generally by the reference number10and is hereinafter referred to as “arbor10.” The arbor10comprises a mounting portion12and a clamping portion14extending from the mounting portion. In the illustrated embodiment, the clamping portion14is cylindrical and comprises an expandable sleeve16which, in use, is at least partially inserted into an aperture defined by the workpiece, and as explained in greater detail below, is caused to engage a wall that defines the aperture. The mounting portion12is coupled to a spindle (shown at15inFIGS. 6 and 7) forming part of the machine tool. During operation of the machine tool, the spindle, and thereby the arbor10, is caused to rotate. The machine tool may be a lathe or any similar type of machine tool having a rotating spindle. Although the arbor10is hereinafter described as receiving a workpiece, it should be understood that the arbor may also be used to receive a tool. While a cylindrical clamping portion14has been shown and described, the present invention is not limited in this regard as other shapes such as square, hexagonal, and the like can also be employed without departing from the broader aspects of the present invention.

As shown inFIG. 2, the expandable sleeve16defines a groove20positioned proximate an end21thereof. A bore17(shown inFIG. 3) extends through the expandable sleeve16. The expandable sleeve16defines a first plurality of slits28that extend longitudinally from the bore17at the end21through a flange24portion and along the expandable sleeve and terminate short of the bore at the second end23. The expandable sleeve16also defines a second plurality of slits29that extend longitudinally from the bore17at the second end23and terminate short of the bore at the end21. As will be explained in detail below, the slits28,29facilitate the expansion of the sleeve to allow the sleeve to expand and engage a workpiece or tool and grippingly retain the workpiece or tool on the sleeve. Materials from which the expandable sleeve16can be formed include, but are not limited to, steel, hardened steel, titanium, and the like. The surfaces of the expandable sleeve16on which the workpiece is received may be coated, grooved, or smooth.

As shown inFIG. 3, the expandable sleeve16is received over a finger30forming part of the clamping portion14. In the illustrated embodiment, the finger30is integrally formed with and extends outwardly from the mounting portion12of the arbor10and along an axis32. Expandable sleeves of different outside diameters can also be received over the finger30to accommodate workpieces having various sizes of internal diameters. Holes38are located in a surface37of the mounting portion12equidistantly about the axis32. Extracting pins39are positioned to slide in each hole38, each extracting pin comprising a head41that, when the extracting pins translate through the holes38, prevents the extracting pins from sliding completely through. A spring36is located inside the mounting portion12to urge the extracting pins39through the holes38. The spring36is positioned in the mounting portion12and retained therein via a closing nut43threadedly engaged in the mounting portion. While the finger30has been shown and described as being integrally formed with the mounting portion12, the present invention is not limited in this regard as the finger can also be threaded onto or otherwise coupled to the mounting portion.

As shown inFIG. 4, the finger30is defined by a shaft portion31having a first tapered portion50on the end of the finger and a second tapered portion52at a base of the finger30proximate the mounting portion12of the arbor10. The present invention is not limited in this regard, however, as only the first tapered portion50may be employed depending on the workpiece being mounted. Incorporation of the second tapered portion52at the base of the finger30, however, allows the expandable sleeve16to expand in a more uniform manner, e.g., substantially the same amount at both ends.

As shown inFIG. 5, once the expandable sleeve16is received over the finger30and is pushed in the direction of the mounting portion12, the flange24engages end portions of the extracting pins39extending out of the holes38. A split ring40is fitted around the expandable sleeve16. The split ring40comprises a first half42and a second half44, each of which is fit around the expandable sleeve16in the groove20. Each half of the split ring40is configured to define a surface48.

As shown inFIGS. 6 and 7, a nut60is received over the expandable sleeve16and against the surfaces48of the split ring40. The nut60is substantially cup-shaped and includes a hole therein to allow the cylindrical portion of the expandable sleeve16to be received therethrough. The flange24, being larger in diameter than the hole through the nut60, does not pass through the nut. The nut60also includes an internal thread62that is receivable on an external thread on the spindle15of the machine into which the mounting portion12is inserted.

To clamp a workpiece on the arbor10, the expandable sleeve16is placed through the nut60, the workpiece is placed on the expandable sleeve16, and the nut60is tightened onto the spindle15. Tightening the nut60onto the spindle15urges the split ring40against the extracting pins39protruding from the holes38, thereby pushing the flange24against the mounting portion12of the arbor10and pushing the arbor into a collet housing64located in the spindle. Further tightening the nut60further draws the flange24against a tapered surface66in the collet housing64. As the flange24is drawn against the tapered surface, the progressive engagement of the flange and the tapered surface66causes the expandable sleeve to move radially outward to engage and releasably retain a workpiece. In configurations in which the second tapered portion52is incorporated into the finger30, the slits28allow for additional radial expansion of the expandable sleeve16proximate the end21.

To unclamp the workpiece, the nut60is loosened on the spindle15, and the spring36urges the extracting pins39in the direction of the clamping portion, which in turn urge the expandable sleeve16off the finger30. In doing so, the expandable sleeve16(with the workpiece clamped thereto) can be removed from the finger30. Upon removing the expandable sleeve16from the finger30and one or more of the first tapered portion50and the second tapered portion52, the slits28,29allow the expandable sleeve16to contract in size across the diameter thereof. As the expandable sleeve16contracts in size across the diameter, the workpiece is released.

Referring now toFIG. 8, another embodiment of the expandable arbor is designated generally by the reference number110and is hereinafter referred to as “arbor110.” The arbor110comprises a mounting portion112and a clamping portion114extending outwardly from the mounting portion, the clamping portion comprising an expandable sleeve16similar to that with regard to arbor10mountable over a finger30. Holes138are located in a surface137of the mounting portion112equidistantly about an axis32extending longitudinally through the arbor110. Springs136are located in each of the holes138such that a portion of each spring extends out of the hole. Upon receiving the expandable sleeve16over the finger30, the portions of each spring136extending out of the holes138are engaged by the end21of the flange24.

As shown inFIG. 9, a split ring40is placed around the expandable sleeve16. A nut60is received over the expandable sleeve16and against surfaces48of the split ring40. As with arbor10, clamping a workpiece on the arbor110involves mounting the workpiece on the expandable sleeve16and tightening the nut60onto the spindle15to urge the split ring40in a forward direction. Upon continued urging of the split ring40, the split ring engages the portions of the springs136protruding from the holes138. Further tightening of the nut60compresses the springs136, pushes the flange24against the mounting portion112, and pushes the arbor110into the collet housing64located in the spindle15. Still further tightening of the nut60further draws the flange24against a tapered surface66in the collet housing64. As the flange24is drawn against the tapered surface, the progressive engagement of the flange and the tapered surface66causes the expandable sleeve16to move radially outwardly to engage and releasably retain a workpiece. In configurations in which the second tapered portion52is incorporated into the finger30, the slits28allow for additional radial expansion of the expandable sleeve16proximate the end thereof.

To unclamp the workpiece, the nut60is loosened on the spindle15, and the springs136urge the flange24and the expandable sleeve16off the finger30. In doing so, the expandable sleeve16(with the workpiece clamped thereto) can be removed from the finger30. Upon removing the expandable sleeve16from the finger30and one or more of the first tapered portion50and the second tapered portion52, the slits28,29allow the expandable sleeve16to contract in size across the diameter thereof. As the expandable sleeve16contracts in size across the diameter, the workpiece is released.

Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.