Spindle locking apparatus for a rotary power tool

A spindle locking apparatus for power tools having a spindle mounted for rotation within a tubular housing. The locking apparatus includes a locking sleeve disposed between the spindle and its tubular housing, a locking collar surrounding the tubular housing radially outboard of the locking sleeve, and a set of drive pins mechanically coupling the locking collar to the locking sleeve through axial slots in the tubular collar. The inner periphery of the locking sleeve is shaped to lockingly engage a flat-sided portion of the spindle, and a spring element biases the locking sleeve away from the flat-sided portion of the spindle to unlock the spindle. The locking collar is axially shiftable against the spring bias as permitted by the slots in the tubular housing to bring the locking sleeve into locking engagement with the flat-sided portion of the spindle to prevent spindle rotation.

TECHNICAL FIELD

This invention relates to power tools having a rotary spindle or shaft, and more particularly to a user-manipulated spindle locking apparatus for selectively preventing spindle rotation.

BACKGROUND OF THE INVENTION

Rotary power tools, particularly those incorporating a collet for securing a drill bit or other rotary bit, will frequently incorporate a drive shaft locking apparatus to enable a user to tighten or loosen the collet without also turning the drive shaft; see, for example, the U.S. Patent No.5,496,139to Ghode et al. Although less commonly, similar locking mechanisms can also be used in connection with angle grinders, routers, and other rotary power tools to enable a user to remove or install an implement such as a grinder wheel or router blade without also turning the spindle. Such locking mechanisms are typically designed into the power tool as an OEM (original equipment manufacturer) feature, and are not readily adaptable for retrofitting an existing power tool. Accordingly, what is needed is a spindle locking apparatus that is suitable for both OEM and retrofit applications.

SUMMARY OF THE INVENTION

The present invention is directed to an improved spindle locking apparatus that is readily adapted to both retrofit applications and OEM applications. The apparatus is designed for use in power tools having a spindle mounted for rotation within a tubular (annular) housing having an axis that coincides with that of the spindle. The spindle is generally cylindrical, but includes a flat-sided (hex-shaped, for example) portion with which the locking apparatus interacts. The locking apparatus includes an axially shiftable locking sleeve disposed between the spindle and its tubular housing, an axially shiftable locking collar radially outboard of the tubular housing and locking sleeve, and a set of drive pins mechanically coupling the locking collar to the locking sleeve through axial slots in the tubular collar. The inner periphery of the locking sleeve is shaped to lockingly engage the flat-sided portion of the spindle, and a spring element biases the locking sleeve (and locking collar) away from the flat-sided portion of the spindle, defining a rest or unlocked position of the apparatus. To lock the spindle, the user shifts the locking collar axially against the spring bias as permitted by the slots in the tubular housing to bring the locking sleeve into locking engagement with the flat-sided portion of the spindle. The spring returns the locking sleeve (and locking collar) to the un-locked position when the user releases the locking collar.

The apparatus is particularly well suited to retrofit applications because the locking sleeve is easily inserted into the space between the spindle and its tubular housing, and because the locking collar can be constructed as a two-piece split ring that is joined to surround the tubular housing. In a preferred embodiment, the split ring halves, when joined, are mutually secured with a one-piece spring steel clamp.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The spindle locking apparatus of this invention is designed for use in power tools having a spindle mounted for rotation within a tubular housing, where it is desirable to temporarily prevent the spindle from rotating with respect to the housing while attaching or removing implements driven by the spindle. One such power tool is an angle grinder having a threaded drive shaft, where abrasive grinding or cutting disks are secured to the drive shaft with a threaded fastener; in such tools, the spindle is mechanically coupled to the drive shaft, and it is desirable to rotationally lock the spindle (and drive shaft) when attaching or removing the threaded fastener.

The locking apparatus of the present invention is illustrated herein in the context of an angle grinder, and the angle grinder's front housing assembly10is shown in the drawings. Referring toFIGS. 1-2, the front housing assembly10includes a tubular housing12and hub14(which are mechanically joined, or formed as one piece as shown), and a guard assembly16mounted on the hub14to partially encircle a grinding or cutting disk (not shown) affixed to a threaded pinion shaft or drive shaft18extending out of the hub14. The tubular housing12includes a first portion12aadjacent the hub14on which the spindle locking apparatus (generally designated by the reference numeral20inFIG. 1) is slidingly received, a second portion12bof larger diameter axially outboard of the first portion12a,and a conical portion12cbridging the first and second portions12aand12b.The free end of the second portion12bis threaded as shown for attachment to the angle grinder's motor housing (not shown).

As seen in the exploded view ofFIG. 2, the front housing assembly10additionally includes a generally cylindrical spindle22supported for rotation within the tubular housing12. The inboard end of spindle22is threaded for attachment to a motor or gearbox output shaft (not shown), and the outboard end is provided with a pinion gear24for engaging a beveled spur gear26(shown inFIGS. 3-5) in hub14. Adjacent the inboard and outboard ends of spindle22are provided front and rear bearing surfaces22aand22b;and between the bearing surfaces22aand22bis a central portion22cthat terminates in a flat-sided feature28that cooperates with the spindle locking apparatus20as described below. The front bearing surface22ais received within a sleeve bearing30(shown inFIGS. 3-5) mounted in tubular housing portion12a,and the rear bearing surface22bis received within a roller bearing32mounted in tubular housing portion12b.

As seen inFIG. 2, the spindle locking apparatus20includes a spiral spring34(preferably a multi-wave disk spring as shown), a locking sleeve36having an inner periphery portion36athat is flat-sided to lockingly engage the spindle's flat-sided feature28, a two-piece locking collar38(comprising the collar halves38aand38b), a pair of drive pins40a,40b,and a spring band42. The spiral spring34and locking sleeve36encircle the spindle22within the tubular housing portion12a,whereas the locking collar38and spring band42encircle the outer periphery of the tubular housing portion12a,radially outboard of the spiral spring34and locking sleeve36. The drive pins40aand40bfunction to mechanically couple the locking collar38to the locking sleeve36so that when the locking collar38is shifted axially on the tubular housing portion12aby a user, the locking sleeve36will correspondingly shift axially in the space between the spindle22and the inner periphery of tubular housing portion12a.The drive pins40aand40bare inserted through a pair of oppositely disposed countersunk openings44formed in the locking collar halves38a,38b,through a pair of oppositely disposed slot openings46formed in the wall of tubular housing portion12a,and into a pair of oppositely disposed openings48formed in the exterior periphery of locking sleeve36. With the drive pins40a,40bso inserted, their heads are received the countersunk openings44, and the spring band42is placed over the outer periphery of the joined locking collar halves38a,38b;this mutually secures the locking collar halves38a,38b,and retains the drive pins40a,40b.

The slot openings46in the wall of tubular housing portion12alimit axial shifting of the locking collar/sleeve assembly due to their interference with the locking pins40a,40b,and also prevent rotation of the assembly with respect to the tubular housing12. The spring34biases the assembly toward an inboard limit position (defined by the inboard end of the slot openings46) in which the inner periphery portion36aof locking sleeve36does not engage the flat-sided feature28of spindle22, leaving the spindle22free to rotate; this state of the spindle locking apparatus20is depicted inFIG. 4. However, the user can axially shift the assembly in the outboard direction until limited by the outboard ends of the slot openings46, thereby bringing the inner periphery portion36aof locking sleeve36into locking relationship with the spindle's flat-sided feature28to prevent rotation of the spindle22with respect to the tubular housing12; this state of the spindle locking apparatus20is depicted inFIG. 5. And when the user releases the locking collar38, the spring34biases the assembly back to the inboard limit position ofFIG. 4, leaving the spindle22free to rotate.

As also seen inFIGS. 3-5, the flat-sided inner periphery portion36aof said locking sleeve36is disposed in a central axial portion of the locking sleeve36, and the drive pins40a,40bare radially aligned with the inner periphery portion36a.Hence, the force exerted by the drive pins40a,40bacts directly on the inner periphery portion36a,which minimizes any non-axial shifting (cocking, for example) of the locking sleeve36when the user axially shifts the locking collar38.

In a preferred embodiment, the locking collar38is constructed by splitting a metal ring of suitable diameter to form the locking collar halves38aand38b.The splitting procedure may be carried out by cutting, for example. Since some material is removed by the splitting procedure, the abutting faces of the locking collar halves38a,38bare recessed (as designated by the reference numeral39inFIG. 2) to partially receive upper and lower spacer pins50a,50b,which introduce a small gap between the abutting faces. As mentioned above, the spring band42mutually secures the abutting locking collar halves38a,38b,and the spring band42is axially retained on the locking collar38by front and rear ridges or shoulders52formed on the locking collar halves38a,38b.The fully assembled locking collar38and spacer pins50a,50bcan be seen in the cross-sectional view ofFIG. 3.

The cross-sectional views ofFIGS. 3-5illustrate how the spindle22and spindle locking apparatus20are supported within the tubular housing12. The front bearing30is disposed within the tubular housing portion12ajust inboard of the pinion gear24, while the rear bearing32is disposed within the larger diameter portion12bof tubular housing12. More particularly, the tubular housing12is provided with an internal shoulder12d,and the rear bearing32and a washer54are trapped between the shoulder12dand a lock nut57threaded into the inner periphery of tubular collar12. The spring34and locking sleeve36of spindle locking apparatus20are disposed about the spindle22within an annular cavity56between the front and rear bearings30and32, with the spring34compressed between the front bearing30and the outboard face of locking sleeve36. While the locking pins40a,40blimit the inboard axial travel of the locking sleeve/collar assembly, the inboard axial face of the locking collar38is conical to match the conical outer periphery12cof tubular housing12to permit sufficient travel of the assembly.

The cross-sectional view ofFIG. 3additionally shows the pinion shaft18, and how it is supported for rotation within the hub14of front housing assembly10. A main pinion bearing60retained within the lower or outboard end of hub14by a lock nut62supports the lower or outboard end of pinion shaft18, and an end cap sleeve bearing64pressed into the upper end of hub14supports the upper or inboard end of pinion shaft18. The beveled spur gear26is disposed just inboard of the main pinion bearing60, and axially retained by a lock nut66threaded onto the pinion shaft18. A spline connection68joins the beveled spur gear26to the pinion shaft18.

In summary, the spindle locking apparatus20of the present invention provides a robust and convenient way for the user of a power tool to rotationally lock the power tool's spindle while changing grinder disks or other implements. The apparatus is particularly well suited to retrofit applications because the locking sleeve36is easily inserted into the cavity56between the spindle22and its tubular housing12, and because the locking collar38is constructed as a two-piece clamshell joined to surround the outer periphery of tubular housing12. Of course, the various elements of the apparatus may be sized differently than shown to suit a given power tool, and may be constructed of metal or plastic, as appropriate. Also, it will be recognized that while the invention has been described in reference to the illustrated embodiments, numerous modifications and variations in addition to those mentioned herein will occur to those skilled in the art. Accordingly, it will be appreciated that systems incorporating these and other modifications and variations still fall within the intended scope of the invention.