Safety chuck

A safety chuck mounted to equipment that process web material is provided. The safety chuck is provided with a die spring connecting a moveable jaw with a spindle, said spring urging the moveable jaw into a fully closed position. A number of magnets mounted on a mounting flange will engage the moveable jaw, overcoming the spring's force and holding the moveable jaw in a fully open position. Rotation of the spindle releases the magnets allowing the spring to force the moveable jaw back into a fully closed position.

BACKGROUND OF THE INVENTION

This invention relates to chucks, and in particular, to safety chucks mounted to equipment that processes web material such as sheets of film, paper, tissue, foil and the like.

During manufacturing and other operations, material may need to be mounted onto or off a roll. In conventional web treatments where machines handle reels of paper, plastics, metal foils, textiles and other sheet material, the cores of these reels must be mounted on the machines so that rotational drive can be selectively coupled to the cores to affect winding or unwinding of the web material entrained on the cores. The cores carrying the webs are normally tubular components. To affect the rotational drive to the core a shaft is generally inserted into and grips the core. Each end of the shaft then engages a chuck attached to a spindle rotationally attached to the machine.

The chucks are termed “safety” chucks when the chucks automatically grasp and close about the shaft ends and, when the machine starts rotating the spindles, prevent the roll from disengaging from the machine. Safety chucks generally are manually closed. If the machine starts with the safety chuck in an open position, prior art safety chucks employ a small sliding cam mechanism to close the safety chuck. These cam mechanisms are not very robust. After a few dozen to a hundred cycles, prior art cam mechanisms wear out. Another problem associated with prior art cam mechanisms is that the safety chuck is not completely closed. As the machine starts rotating, wear on the cam mechanism increases, thereby increasing the cumulative wear on the cam mechanism, shortening its life span.

SUMMARY OF THE INVENTION

The present invention overcomes the limitations of prior art safety chucks by providing a safety chuck which incorporates a closing spring(s) and magnets. An operator will manually open the safety chucks, applying force against the spring(s). In the full open position, magnets will make contact and hold the safety chuck in the full open position. A shaft is then inserted into a safety chuck pair. The machine is started. As the safety chuck with mated shaft turns, the magnets slide apart and release. The spring(s) then force the chuck fully closed.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings in detail wherein like elements are indicated by like numerals, there is shown a safety chuck1comprising a spindle10, held by a mounting flange20, said spindle terminating in a jaw assembly40.

The spindle10has an elongated, generally cylindrical body11with a proximal end12and a distal end13, said proximal and distal ends defining a spindle longitudinal axis. The spindle body11is held by an annular mounting flange attachable to a work machine frame (not shown). A jaw assembly40is attached to the spindle distal end13. The spindle body11has a key way14adapted to engage a work machine rotational element (not shown). The key way14is an elongated channel along a spindle body surface15parallel to the spindle longitudinal axis, said key way beginning near to the spindle proximal end12.

The annular mounting flange has a cylindrical housing29leading to a rear surface24, said rear surface24facing the spindle proximal end12. The mounting flange has a front surface25formed into a flange in front of the housing29. The annular mounting flange20has a central, ring-like aperture21formed therein. The spindle body11fits within the aperture21. Three rings of ball bearings, two forward rings22aand22b, and a rearward ring23are positioned within the aperture21against the spindle surface15beneath the housing29. A retaining clip35holds the bearings22&23in place about the central aperture21. An annular dust shield26is placed within the aperture21beneath the housing29at the main body rear surface24to protect the ball bearing rings22,23. Attachment means27are provided within the annular mounting flange, said attachment means adapted to provide attachment to the work machine frame (not shown). The annular mounting flange20supports a rotating spindle10without itself moving, the ball bearings allowing spindle rotation while also providing spindle support. The spindle distal end13terminates within the annular mounting flange central aperture21past the mounting flange front surface25.

The jaw assembly40is comprised, in part, of a static jaw41fixedly bolted44to the spindle10and extending forward of the spindle distal end13. The jaw assembly is also comprised of a complimentary moveable jaw42encased in a moveable, cylindrical shroud50. The shroud50has a rear surface51, facing the mounting flange front surface25, and an opposite front surface52. The shroud50has a central aperture53with the attached moveable jaw42fixedly attached thereto. The shroud central aperture53is slideable over the spindle front distal end13and static jaw41, through the mounting flange front surface25, a desired distance into the mounting plate interior28. The shroud50is in a fully closed position when the shroud is forward enough that the moveable jaw42is aligned with the static jaw41.

The spindle distal end13has a spring aperture17formed therein, said aperture17off-center from a central spindle longitudinal axis. The moveable jaw42has a corresponding spring aperture43formed therein. A single die spring18is inserted into the spring apertures17,43, said spring18forcing the shroud50into a fully closed position, thereby locking the jaws41,42onto a shaft end.

The mounting flange20has a plurality of magnets30attached thereto about the central aperture21and facing toward the shroud rear surface51. The shroud rear surface51is made from ferrous material55. The shroud faceplate ferrous rear surface55has a plurality of open slots56formed therein, said slots spaced about the faceplate rear surface51. The magnets30are adapted to magnetically engage the faceplate ferrous rear surface55when the faceplate rear surface51engages the mounting flange interior28. SeeFIG. 7. As the shroud50is rotated and the magnets30are aligned with the faceplate open apertures56, the magnetic engagement is broken. SeeFIG. 8.

The magnetic engagement is most powerful when there is direct contact, however the resulting normal force of direct contact would create friction resistance, which would increase the required torque that needs be transmitted between the safety chuck to the shaft over to the other safety chuck. Therefore, a separation, i.e., a few thousandths of an inch, between the magnets and the shroud ferrous rear surface55is desired. Furthermore, the magnets are brittle, so it is desirable that the magnets not actually touch the shroud ferrous surface55. To prevent actual touching between the magnets30and the faceplate ferrous rear surface55, a non-ferrous mechanical stop57is formed on the mounting flange about each magnet30, thereby controlling the closeness of the magnets30to the ferrous material55when the faceplate50is in an open position. The mechanical stop restriction prevents the magnets from scraping against the faceplate ferrous material55and overcoming inertia.

In operation, the rotation of the shaft within the safety chuck1ceases. The shroud50is manually moved from a closed position to an open position, thereby moving the moveable jaw42away from the static jaw41. The mounting flange magnets30engage the shroud rear surface ferrous material55, thereby overcoming the spring18tension and holding the shroud50open. When a new shaft is placed onto the static jaw41, rotation of the shroud50brings the shroud rear open apertures56into alignment with the magnets30, thereby breaking the magnetic attraction holding the shroud and attached moveable jaw in an open position. The tension of the spring18forces the shroud50and moveable jaw42forward into a closed position bringing the two jaws41,42into alignment over the shaft end.

The advantage of the off-center spring location is that the spring18is in direct alignment with the moveable jaw42. However, the invention structure must accommodate commercially available springs. For a wider latitude in spring selection, the spring location may be aligned with the central longitudinal axis of the spindle.

Referring to the drawings in detail, with specific emphasis onFIGS. 9-11, there is also shown a safety chuck1with a central spring arrangement. The spindle distal end13has a spring aperture17formed therein, said aperture17formed along a central spindle longitudinal axis. The moveable jaw42has a tab45fixedly attached to a rear moveable jaw portion46, said tab extending radially toward a mounting flange central axis. The tab has a spring aperture47corresponding to the spindle spring aperture17. A single die spring18is inserted into the spring apertures17,47, said spring18forcing the moveable jaw42and attached shroud50forward into a fully closed position, thereby locking the jaws41,42onto a shaft end. SeeFIG. 9.

The mounting flange20has a plurality of magnets30attached thereto about the central aperture21and facing toward the shroud rear surface51. The shroud rear surface51is made from ferrous material55. The shroud faceplate ferrous rear surface55has a plurality of open slots56formed therein, said slots spaced about the faceplate rear surface51. The magnets30are adapted to magnetically engage the faceplate ferrous rear surface55when the faceplate rear surface51engages the mounting flange interior28. SeeFIG. 10. As the shroud50is rotated and the magnets30are aligned with the faceplate open apertures56, the magnetic engagement is broken. SeeFIG. 11.

It is understood that the above-described embodiments are merely illustrative of the application. Other embodiments may be readily devised by those skilled in the art, which will embody the principles of the invention and fall within the spirit and scope thereof. It may be desirable to install a redundant cam60in the mounting flange20in case of spring failure. The faceplate open apertures56may be replaced with sections of non-ferrous material. A seal, wiper or brush may be installed within the safety chuck to keep debris off of the magnets. Other spring and/or magnet configurations may be used to obtain the same functionality as described above.