US20080014844A1

US20080014844A1 - Power tool with spindle lock

Info

Publication number: US20080014844A1
Application number: US11/879,363
Authority: US
Inventors: James Matthew Pontieri
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-17
Filing date: 2007-07-17
Publication date: 2008-01-17

Abstract

A spindle lock equipped hand-held power tool, such as a grinder or circular saw, includes a housing assembly, a motor including a rotating armature shaft, a spindle carried externally of the housing adapted for selectively affixing and releasing a rotating cutting tool and a drive train which drivingly interconnects the motor armature shaft and spindle for the application of torque to the tool upon electrical energization of the motor. A lock member carried in the housing is selectively displaceable along a fixed axis between a locked position wherein it engages a rotating element of the drive train to prevent rotation of the spindle, and a released position. A spring continuously urges the lock member toward the released position. A manually operable lever selectively displaces the lock member between the released and locked positions.

Description

RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application No. U.S. Ser. No. 60/831,436, entitled “POWER TOOL SPINDLE LOCK” filed 17 Jul. 2006.

TECHNICAL FIELD

The present invention relates generally to hand-held power tools, and, more particularly, to such tools which include a driven spindle configured for drivingly engaging a sacrificial cutting or forming accessory.

BACKGROUND OF THE INVENTION

Hand-held grinders are common tools that are used for a variety of applications. Typically, a grinder includes a motor that drives a wheel (such as a grinding wheel, wire brush, or cutting disc). Many grinders include a drive shaft from the motor and a gear system coupled to the drive shaft that changes the direction of rotation. Often, the direction of rotation is changed by 90°. Also, many grinders include a lock pin that can be pressed inwardly to lock the drive shaft relative to the housing of the grinder so that a clamping screw can be loosened or tightened to mount the wheel on the grinder or remove the wheel from the grinder.
Hand held grinders are useful because they are portable and, thus, can be taken to the part to be worked, rather than the part having to be moved to a stationary grinder. Such grinders are often useful in working surfaces of large or bulky machines or parts. As such, they are often used in automobile repair, metal fabrication, welding shops, heavy equipment repair, and woodworking. However, previously known hand grinders have not been able to reach many hidden or obstructed work surfaces or have required excessive work or modification to reach many work surfaces.
U.S. Pat. No. 6,386,961 B1 to Cureton discloses a hand-held grinder which includes a motor and a mounting surface coupled to the motor. A housing supports the mounting surface and the motor. A grinding wheel abuts and is secured to the mounting surface, and the grinding wheel extends beyond an end of the housing. A line that is tangential with the grinding wheel distal from the housing, and that is tangential with the end of the housing, may be at an angle of less than about 45° relative to a plane of rotation of the grinding wheel. The grinder may also include a drive shaft coupled to the motor, a driving gear coupled to the drive shaft, and a driven gear engaging the driving gear and fixed to the mounting surface. The driven gear and the mounting surface are part of a unitary member. The housing defines a bottom housing surface that is substantially coplanar with the mounting surface. The housing defines a tapered end. The grinder includes a telescoping feature wherein the housing includes a first member that is movable relative to a second member to change the length of the grinder. The grinder includes a lock pin that is selectively forced into engagement with the drive shaft, thereby preventing rotation of the drive shaft relative to the housing.
In other power tools, such as a circular saw or router, an internal electric motor has a rotating shaft coupled to a cutting tool at an exposed end. These cutting tools are selectively mounted to or removed from the shaft depending upon the work to be performed by the cutting tool. It is a convenience to the operator, if the rotation of the shaft can be inhibited during the mounting or removal of the cutting tool since the mounting or removal of the cutting tool requires rotary motion about an axis concentric with the shaft. Preferably, the mechanism for locking the shaft should also inhibit electrical power from being applied to the electric motor when the rotation of the shaft is inhibited to prevent damage to the motor or causing it to overheat.
Shaft locking mechanisms which include electrical cut-out switches to prevent electrical power from being applied to the motor when the shaft is locked are known in the art. U.S. Pat. No. 2,897,302 to Godfrey et al. discloses a control mechanism for an ON/OFF switch of a router which automatically locks the shaft when the electrical switch is placed in the OFF position and release the shaft when the electrical switch is placed in the ON position. In an alternate arrangement disclosed in U.S. patent application Ser. No. 07/764,239, filed 23 Sep. 1991 to McCurry, a shaft lock mechanism has a first position in which the shaft is locked and a cut-out switch is placed in an open position. The shaft lock mechanism is manually displaceable to a second position in which the shaft is free to rotate and the cut-out switch is placed in a closed position.
U.S. Pat. No. 5,346,342 to Winchester discloses a shaft lock arrangement having a shaft lock slidably mounted in the housing of a power tool. The shaft lock has a keyhole-shaped aperture having a circular portion circumscribing the output shaft of the power tool when the shaft lock is in the RUN position and a rectangular portion, the sides of which straddle flat portions of the output shaft preventing the output shaft preventing the output shaft from rotating when the shaft lock is in the LOCKED position. The shaft lock further has a run detent resiliently engaged by a toggle of a cut-out switch to hold the shaft lock in the RUN position and a lock detent resiliently engaged by the toggle of the cut-out switch to hold the shaft lock in the LOCKED position. The cut-out switch prevents electrical power from being applied to the motor of the power tool when the shaft of the power tool is locked by the shaft lock.
With devices such as hand-held power tools such as power screwdrivers, it is well known that the torque or force which must be applied to a screw can vary substantially as the screw is advanced into, or removed from, anchoring engagement with an associated work piece. In particular, very large forces may be required to ultimately “set” the screw during installation or to initially “break loose” the screw during removal. Difficulties have been encountered in generating these large driving forces, particularly in small hand-held tools where size and weight considerations necessarily limit the available motor horsepower. The problem is further aggravated where a cordless battery tool operation is contemplated. In such a tool it has been found that batteries of sufficient electrical capacity to power a high-torque cordless screw-driver tool are impractical due to inherent size and weight limitations. This is particularly true with respect to light duty power tools which feature compact, lightweight construction.
U.S. Pat. No. 4,804,048 to Porth, Jr. Proposes a solution to the low torque problem by providing a hand-held power tool including a spindle which is adapted to receive and retain tool bits for rotation thereon. A collet ring is retained with a recess on the tool housing for slidable movement along the spindle axis. The collet functions as a selectable spindle locking device whereby the tool may be operated as a manual screwdriver or the like by selectively positioning the collet to rigidly lock the spindle in a fixed relationship to the tool housing.
In manual work, for instance, by attaching various tools by mounting a chuck on the output shaft of a power tool, if the power switch is turned off, the output continues to rotate by inertia of the chuck or tool, and if the power tool is released from the user's hand during this rotation, the tool is still rotating and can pose a risk of injury. It is therefore preferred that the output shaft be stopped immediately when the power switch is turned off.
In a chuck, there is known a chuck with a torque-up function capable of tightening or detaching the tool, only by turning the operation ring by hand, without having to use a chuck handle, but when using such chuck with torque-up function, while the motor source is off, the output shaft of the power tool is free to rotate. If an attempt is made to tighten the chuck by hand, the output shaft also rotates and it cannot be tightened by hand. Hence it is necessary to fix the output shaft by one hand, and the controllability is poor because of hand tightening of the chuck and holding of the tool. Accordingly, it has been proposed that the output shaft of the power tool be locked while the motor power source is off.
U.S. Pat. No. 5,732,805 to Nakamura discloses a lock device of an output shaft which is capable of stopping the output shaft quickly when the output shaft is controlled to stop, and locking to prevent the output shaft from rotating when the output shaft side is stopped against the drive side. The output shaft is formed by connection of the drive shaft and a driven shaft. Play for a predetermined relative angle is formed in a mutual rotating direction, at a junction of connection of the drive shaft and driven shaft. A holding plate is fixed to the driven shaft side confronting the drive shaft in the axial center direction. An annular lock ring forming a lock pawl on the outer circumference is held movably to a concentric position and an eccentric position, at the holding plate side. A lock operation member is provided on the drive shaft confronting the lock ring, for allowing the lock ring to move to the concentric position when the play at the junction of the drive shaft and driven shaft is eliminated by initial rotation or rotation of the drive shaft, and allowing movement to the eccentric position when rotation of the drive shaft is stopped to reestablish a play at the junction by reaction. An internal ring forming a pawl for locking mutual rotation by mutually engaging with the lock pawl on the outer circumference of the lock ring when the lock ring is moved to the eccentric position is formed oppositely on the outer circumference of the lock ring.
The present invention is an improved shaft lock mechanism for a power tool which overcomes many of the shortcomings of prior art approaches.

SUMMARY OF THE INVENTION

An object of the present invention is to develop a spindle locking mechanism for a hand-held power tool which employs a manually operable lever which displaces a locking pin between a retracted position which frees the spindle drive to rotate a tool, and a locked position which prevents rotation of the associated tool spindle, for repair or replacement of the tool, or the like.
According to the present invention, a hand-held power tool includes a housing assembly, a motor with a rotating armature shaft disposed within the housing assembly, a spindle carried externally with the housing assembly for relative rotation about a drive axis and a drive train interconnecting the motor armature shaft and spindle for the application of torque therebetween upon electrical energization of the motor. A lock member

FIG. 8, is a broken, cross-sectional view of a further alternative lock member construction including a rotating ball-type cam follower feature;

FIG. 9, is an alternative embodiment of the present invention wherein the spindle-lock feature is adapted for aftermarket applications with a hand-held power tool;

FIG. 10, is another alternative embodiment of the present invention wherein the spindle-lock feature is also adopted for an aftermarket application with a hand-held power tool;

FIG. 11, is a cross-sectional view of an alternative “wrench-type” interconnection between the rotating transmission element and lock member;

FIG. 12, is a broken, cross-sectional view of still another embodiment of the invention, similar in some respects to the embodiment of FIG. 9, but with a ramp-type lock member actuator incorporated within the lever;

FIG. 13, is a bottom side plan view of the lever of FIG. 12; and

FIG. 14, is a cross-sectional view taken on lines 13-13 of FIG. 13, on an enlarged scale, illustrating the arcuate ramp feature of FIGS. 12 and 13.

Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to illustrate and explain the present invention. The exemplification set forth herein illustrates an embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PREFERRED AND ALTERNATIVE EMBODIMENTS

For purposes of illustration, the present invention is implemented within a specific type of hand-held power tool, in particular, a hand-held industrial grinder. However, it can be applied with equal success with other commercial or light duty hand-held power tool types such as a circular saw, drill, screw driver, or the like. is carried with the housing assembly which is selectively displacable along a fixed axis between a locked position in which a first end portion of the lock member engages a rotating element of the drive train to prevent rotation of the spindle, and a released position in which the first end portion of the lock member is spaced from the rotating element to permit rotation of the spindle. Resilient means, such as a compression spring, continuously urges the lock member toward the released position to provide fail-safe operation. Finally, a lever is carried externally of the housing assembly and engages the lock member. The lever is manually operable to displace the lock member from the released position to the locked position.
The spindle locking assembly provides mechanical advantage for the user and is “bi-stable”, meaning that it can positively position the locking pin in both the engaged and released positions for “hands free” operation/service of the power tool. Furthermore, the structure of the lever overlays the locking pin when in either the engaged or released position to prevent accidental or inadvertent displacement of the lock pin during use or handling of the power tool.
According to an aspect of the invention, the lever is operatively carried with and extends radially outwardly from the lock pin. This has the advantage of providing a single, compact inexpensive structure.
According to another aspect of the invention, the lever has a handle portion and a cam portion mounted for limited rotation adjacent an outer surface of the housing assembly whereby the cam portion remains in sliding engagement with the second, outer end portion of the lock member. This has the advantage of enabling packaging of the lock mechanism within niches or recessed features of the power tool.
According to still another aspect of the invention, the handle portion of the lever is nestingly recessed within a similarly contoured pocket formed in an external surface of the housing assembly when in the release position and projects radially outwardly when in the engaged position. Optionally, a highly visible flag is carried of the handle portion which alerts the operator when the locking mechanism is engaged. Also optionally, an electrical motor drive disabling circuit can sense the position of the lever and disable energization of the motor whenever the lever is not in the release position.
These and other features and advantages of this invention will become apparent upon reading the following specification, which, along with the drawings, describes preferred and alternative embodiments of the invention in detail.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1, is a side plan view of the preferred embodiment of the present invention embodied in a hand-held power grinder;
FIG. 2, is a cross-sectional view taken on line 2-2 of FIG. 1, on an enlarged scale, illustrating structural details of the spindle lock of the present invention;
FIG. 3, is a broken, cross-sectional view taken on line 3-3 of FIG. 2, on a further enlarged scale, illustrating additional details of the spindle lock of the present invention;
FIG. 4, is a broken, partial cross-sectional view of the spindle lock of FIGS. 1-3 on a still further enlarged scale illustrating the selective juxtaposition of the manually operated lever between a stowed (released) position, a fully rotated (engaged) position (in phantom) and an intermediate, maximum lock member extension position;
FIG. 5, is a graphical depiction of the relative displacement of the lock member vis-a-vis the lever of the apparatus of FIG. 4;
FIG. 6, is a simplified, broken, cross-sectional view of an alternative embodiment of the present invention including a schematic diagram of the motor and its associated electrical control circuit;
FIG. 7, is a broken, cross-sectional view of an alternative lock member construction including a rotating cylindrical cam-follower feature;
An essential advantage of the resent invention is that it provides a robust locking mechanism for temporarily disabling rotation of an output shaft, chuck or spindle while being fitted with a rotating tool such as a grinding/cutting disc, circular saw blade, drill bit, drive bit, or the like. This is particularly advantageous in applications with high performance hand-held grinders where relatively high levels of torque are required to disassemble/reassemble the drive spindle upon fitting or replacing a consumable grinding disc.
Although spindle locks for such hand-held tools have been previously proposed, such solutions require relatively great manual dexterity and prolonged application of force by one or both hands to maintain the locking condition. This leaves only one free hand to affect the (re) assembly of the spindle and cutting tool. The problem is exacerbated by high force compression springs within the tool which must be continuously manually compressed by the application of force along a defined axis during the (re) assembly process. Prior motor housings, combined with cutting/grinding guides and safety guards frequently make access to the spindle lock awkward at best.
Referring to FIG. 1, a heavy duty hand-held grinder 10 is illustrated, including a housing assembly 12, a grinding wheel 14 mounted for rotation with an external spindle 16 about a fixed axis A-A′, and a guard assembly 18. For the sake of simplicity of illustration, non-essential structural details, such as mechanical fasteners, are not included in this description. The inventor directs the reader to the descriptive materials contained in the background references discussed hereinabove.
The housing assembly 12 includes an electric motor 20 interconnected to a transmission housing 22 by an intermediate input collet 24. The transmission housing 22 is also interconnected to the guard assembly 18 by an intermediate output collet 26. The electric motor 20 is electrically powered by a source of electrical potential by an electrical cable 28 and terminating plug 29 or, alternatively, a battery pack. As described hereinbelow in greater detail, electric motor 20 includes an electric control circuit 30 (refer FIG. 6) including a manually operable “on-off” switch 32. Although not illustrated, it is contemplated that the control circuit 30 can also have additional manual control features such as direction of rotation control (i.e. forward/reverse), variable speed, torque limit, and the like.
Referring to FIGS. 1 and 6, the electrical motor has a rotating armature 34 carrying a drive shaft 36 which extends through input collet 24 for driving a speed reducing gear set 38 within transmission housing 22. A transmission output shaft 40 exits transmission housing 22, extends through output collet 26, and drivingly carries external spindle 16 for rotation about axis A-A. The drive shaft 36 of electric motor 20 extends substantially horizontally as depicted in FIG. 1, which is normal to the drive axis A-A. Note that certain structural features such as bushings, bearings, seals and the like are not illustrated for the sake of clarity of understanding of the present invention.
Referring to FIG. 1, the grinder 10 is equipped with one or more hand grips 42, affixed to and extending outwardly from (out of the plane of the paper of FIG. 1), for enabling the user to firmly support and guide the grinder 10. Hand grip 42 is constructed of a rigid inner shaft with an elastomeric outer cover including an integral thumb guard 44.
Definitionally, the housing assembly 12 of the hand-held grinder 10 consists of a single unified structure including the electric motor 20, the transmission housing 22, the inlet and outlet collets 24 and 26, respectively, and the guard assemble 18, as well as other internal and incidental elements carried therewith. The stator portion of the electric motor 20 is rigidly affixed to the remainder of the housing assembly 12. Alternatively, the entire motor assembly 20, including the armature 34, drive shaft 36 and stator could be secured within the housing assembly 12. The guard assembly 18 may be adjustable with respect to the grinding wheel 14 as well as the remainder of the housing assembly 12 to expose more or less of the grinding wheel 14. Furthermore, guides (not illustrated) can also be provided to orientate the hand-held grinder 10 with respect to a work piece.
The free end of transmission output shaft 40 extends through a registering passageway (not illustrated) in the guard assembly 18 and supports the external spindle 16. The spindle consists of a base or hub portion 46 affixed to the output shaft 40 for rotation therewith and a removable retainer 48 such as a spanner nut. The removable retainer 48 can be threadably affixed to the output shaft 40 and cooperates with the base portion to axially restrain the grinding wheel 14 in its illustrated position. As illustrated in the installed position, the grinding wheel, the base portion 46 and the retainer 48 rotate as a single unit with output shaft 40, as driven by the electric motor 20 through the gear set 38 within the transmission housing 22.
During use, the grinding wheel 14 is consumed or worn as a result of abrasively engaging work pieces. Accordingly, the grinding wheel 14 must be replaced or rebalanced from time to time. This is accomplished by removing the retainer 48 from the end of the output shaft 40. The worn grinding wheel 14 is then removed and replaced with a new unit. Subsequently, the retainer is reapplied to its illustrated position. Removal and reapplication of the retainer 48 requires the application of relatively high levels of torque about the output shaft 40. Typically a special tool or wrench is employed to enhance mechanical advantage.
A problem can arise during the removal and replacement of the retainer 48 wherein torque applied thereto can also rotate the output shaft 40, the gear set 38, the drive shaft 36 and the armature 34 of the electric motor 20. This can be dangerous if the electric motor is inadvertently energized at the same time and can result in damage to the transmission gear set 38 inasmuch as such tools such as grinder 10 are designed for drive torque to flow from the electric motor 20 to the grinding wheel 14, not the reverse.
A solution to the forgoing problem solved by the present invention is in the provision of a spindle lock mechanism 50 which temporarily engages and locks a rotating element such as the output shaft 40 during mounting of the grinding wheel 14. This prevents back-drive or torque from damaging the gear set 38 or other portions of the grinder 10 when the grinding wheel 14 is being mounted/removed. This also prevents inadvertent energization of the electric motor 20 (and resulting spin-up of the grinding wheel 14) during the servicing process. Although the spindle lock mechanism 50 can be configured to engage any element of the drivetrain interconnecting the motor armature 34 and the spindle 16, it is preferably carried by a portion of the housing assembly 12 nearest the external spindle 16.
Referring to FIGS. 1-3, the spindle lock mechanism 50 is positioned in an axially central, reduced diameter portion 52 of output collet 26 intermediate opposed, increased diameter mounting flanges 54 and 56. Mounting flanges 54 and 56 are integrally formed with central portion 52 and employed for affixation with the transmission housing 22 and guard assembly 18, respectively. The flanges 54 and 56 also serve to protect the spindle lock mechanism 50 from impact damage during normal usage of the hand-held grinder 10 as well as unintended locking engagement with the drivetrain elements.
The spindle lock mechanism consists 50 of a lock pin 58 and a lock lever 60. The lock pin 58 is generally shaped as an elongated cylinder and extends through a stepped radial passageway 62 in the central portion 52 of the output collet 26. The stepped passageway 62 defines a fixed axis B-B which normally intersects the axis of rotation A-A of the output shaft 40. A plurality of locking recesses 64 are formed in the outer circumferential surface of the output shaft 40, configured as outwardly opening blind bores which rotate in periodic register with passageway 62. The lock pin 58 has a first, inner end portion 66, a second, outer end portion 68 and an intermediate radially outwardly directed, stepped collar 70 of increased effective diameter. Passageway 62 extends radially between an outer opening 72 on the outer circumferential surface and an inner opening 74 on the inner circumferential surface of the central portion 52 of the output collet 26. Passageway 62 forms a radially inwardly directed step 76 adjacent inner opening 74 and a radially outwardly directed circumferential groove 78 adjacent the outer opening 72. A snap ring 80 is disposed within groove 78 and extends radially within passageway 62.
When assembled, the lock pin 58 is free for limited radial displacement within passageway 62 between a radially outwardly most (hereinafter “released”) position wherein the stepped collar 70 abuts snap ring 80 and a radially inwardly most (hereinafter “locked”) position. A compression spring 82 is disposed within passageway 62 continuously resiliently urging radially inwardly against radial step 76 and radially outwardly against stepped collar 70 of lock pin 58. The lock pin radially inwardmost position is defined as the position where the compression spring 82 is substantially or fully compressed.
The outer end portion 68 of lock pin 58 has a plastic or nylon button 84 (hereinafter “cam follower”) affixed thereto.
Lock lever 60 is a crescent shaped rigid structure including a handle portion 86 and a cam portion 88 integrally formed together and nestingly disposed within a circumferentially elongated pocket or recess 90 formed in the central portion 52 of the outlet collet 26. A bore 92 extends through the cam portion 88 of the lock lever 60. An axle pin 94 extends through bore 92. Opposed ends 96 and 98 of axle pin 94 extend within registering opposed blind bores 100 and 102 formed within associated localized flanges 104 and 106, respectively, integrally formed with and extending radially outwardly from the outer circumferential surface of the central portion 52 of the output collet 26. Thus configured, the lock lever 60 is affixed to the housing assembly 12 and displacable about an axis C-C defined by the axle pin 94 between first and second end limits of travel. Axis C-C is parallel to axis A-A and intersects axis B-B.
The outer opening 72 of passageway 62 opens within an end of the crescent shaped recess 90 associated with the axle pin 94.
The lock lever 60 and the crescent shaped recess 90 are dimensioned and configured for nesting disposing of the lock lever 60 substantially entirely within the recess 90 when oriented as illustrated in FIG. 2. When so disposed, the lock lever 60 is substantially obscured from view of the operator of the hand-held grinder 10.
The cam portion 88 of the lock lever 60 has an irregularly shaped caming surface 108 extending generally circumferentially partially about axis C-C. As best illustrated in FIG. 3, the caming surface is concave and configured to slidingly engage the crowned or convex upper surface of the cam follower 84. The compression spring 82 continuously maintains the cam follower 84 of the lock pin 58 in continuous contact with the caming surface 108 of the lock lever 60.
Referring to FIG. 2, the caming surface 108 is separated into three distinct portions or lobes, a minimum radius portion 110, a maximum radius portion 112 and an intermediate radius portion 114. The portions 110, 112 and 114 are a single, continuous contoured peripheral surface 108 of the cam portion 88 of the lock lever 60. Preferably, caming surface 108 is longitudinally convex, as is best viewed in FIG. 3 to maintain precise alignment of the cam portion 88 of lock lever 60 and the outer end portion 68 of the lock pin 58 for smooth rolling or sliding interface therebetween.
Referring to FIG. 4, basic operation of the spindle lock mechanism 50 is illustrated. The spindle lock mechanism 50 provides a manually operated device for selectively locking the output shaft from rotation. When the lock lever 60 is in the position illustrated in FIG. 2, the compression spring 82 maintains the lock pin 58 in the illustrated release position. The lock lever 60 is unobtrusively stowed within the shaped recess 90 and the hand-held grinder is available for normal operation. In this position, the minimum radius portion 10 of the caming surface 108 of the lock lever 60 is in contact with the cam follower 84 and the lock pin 58 is maintained in the release position by the compression spring.
When an operator desires to change out the grinding wheel 14, he (after taking the safety step of unplugging the electrical plug 29 from any source of electrical potential) manually pivots the lock lever 60 from the orientation illustrated in solid line in a counter-clockwise direction about axle pin 94. After being pivoted approximately 90° (as illustrated in phantom as lever lock 60′), the maximum radius portion 112 of the caming surface 108 of the lock lever 60 is in contact with the cam follower 84. The increased radius of this portion of the caming surface profile 108 displaces the locking pin 58 inwardly to its point of maximum displacement designated by arrows 116. In this position, the inner end portion 66 of the lock pin 58 is displaced inwardly, traversing the radial gap 118 between the outer circumferential surface of the output shaft 40 and the inner circumferential surface of the central portion 52 of the output collet 26 and penetrating into a registering locking recess 64 in output shaft 40. If the locking recess 64 is not initially aligned with the lock pin 58, the grinding wheel 14 can be manually repositioned to affect such alignment.
Because the cam face profile slopes away in both circumferential directions at this point, the operator continues to further rotate the lock lever 60 an additional approximately 30° wherein the lock lever 60 is at the fully clockwise position (as illustrated in phantom as lever lock 60″). In this intermediate engaged position, the intermediate radius portion 114 of the caming surface profile 108 engages the cam follower 84. Insodoing, the compression spring 82 displaces the lock pin 58 radially outwardly to the position illustrated by the second phantom depiction designated by arrows 120. Although the lock pin 58 has been partially remover from the locking recess 64, it is still fully operative to positively lock the output shaft from rotation (as illustrated in phantom as end portion 66″).
When in the stowed (lock pin 58 is released) position, the handle portion 86 of lock lever 60 is filly disposed within the recess 90. The handle portion 86 has a circumferential outer surface 121 which is preferably substantially flush with the outer circumferential surface 53 of the central portion 52 of the output collet 26. A circumferentially extending nib 123 extends from the free end of the handle portion 86 of lock lever 60 to facilitate grasping the handle portion 86 with, for example, the tip of an operator's finger. This eliminates the need for a separate release tool and minimizes the chances of accidental or inadvertent release.
When the change out of the grinding wheel 14 is complete, the operator simply manually rotates the lock lever counter-clockwise to its initial (solid line) position. Thereafter, he is free to reinstall the plug 29 and continue use of the grinder 10.
An attention attracting flag 122, such as a brightly colored adhesive sticker or the like is provided on a side wall 124 of the handle portion 86 of the lock lever 60. When the lock lever 60 is in the release position within the recess 90, the flag 122 is obscured from view. However, whenever, the lock lever 60 is partially or fully deployed toward the engaged position, it is highly visible, providing a safety warning to the operator.
Referring to FIG. 5, a graphical depiction of the relative displacement of the lock pin 58 or plunger versus the lock lever 60 illustrates the “over-center” operation of the spindle lock mechanism 50. As the lock lever 60 is displaced from the release position to the lock position, the lock pin 58 is displaced from a minimum deployment position to a maximum deployment position and, finally, to an intermediate deployment position. This illustrates the bi-stable operation of the spindle lock mechanism, in both limits of travel of the lock lever 60.
Referring to FIG. 6, a schematic diagram of the control circuit 30 is illustrated. A cut-out switch 126 is incorporated within the housing assembly 12 which is electrically in series with the on-off switch 32 and the electric motor 20. The cut-out switch 126 includes a mechanical actuator 128 forming leading and trailing ramped surfaces 130 and 131, respectively, extending into the crescent recess 90 for receiving the handle portion 86 of the lock lever 60. A compression spring 132 continuously urges the actuator 128 into a position (illustrated) wherein the ramped surfaces 130 and 131 extend into the recess 90, and thereby opening the contacts of the cut-out switch 126. Whenever the handle portion 86 of the lock lever 60 is rotated out of the recess 90, the compression spring 132 displaces the mechanical actuator 128 into the illustrated position, disabling the control circuit 30. When the handle portion 86 of the lock lever 60 is returned to its stowed position within the recess 90 as illustrated in FIG. 2, it interferes with the mechanical actuator 128 and, by virtue of the ramped surfaces 130 and 131 displaces the mechanical actuator 128 rightwardly from its illustrated position, closing the contacts of the cut-out switch 126 and re-enabling operation of the control circuit 30.
A notch or detent recess 125 is formed in the side wall 124 of the handle portion 86 to permit slight leftward displacement of mechanical actuator 128 by registering with the mechanical actuator 128 whenever it is in the stowed position. This slight leftward displacement provides a mechanical detent function, retaining the handle portion 86 in its stowed position without opening the electrical contacts of the cut-out switch 126. A similar mechanical detent can also be provided between the cam portion 88 of the lock lever 60 and a sidewall of the recess 90 when in the fully deployed or intermediate positions.
Referring to FIG. 7, an alternative design lock pin 134 is illustrated. Lock pin 134 is similar to lock pin 58 described in connection with FIGS. 1-5 in all material respects, with the sole exception that the outer end portion 136 of lock pin 134 is provided with a roller-follower 138 carried for rotation about an axle 140 carried by spaced, integrally formed ear extensions 142. In this embodiment, the outer peripheral surface of roller-follower 138 remains in continuous rolling contact with the cam portion profile 108 of the associated lock lever 60. The roller-follower can be constructed of steel, nylon or other suitable material.
Referring to FIG. 8, a second alternative design lock pin 144 is illustrated. Lock pin 144 is similar to lock pin 58 described in connection with FIGS. 1-5 in all material respects, with the sole exception that the outer end portion 146 of lock pin 144 is provided with a roller ball 148 retained loosely within a pocket 150 and retained therein by a swedged edge 152 circumscribing the pocket 150. In this embodiment, the outer peripheral surface of the roller ball 148 remains in continuous rolling contact with the cam portion profile 108 of the associated lock lever 60. The roller ball 148 can be constructed of steel, nylon or other suitable polymeric material.
Referring to FIG. 9, an alternative embodiment of the invention is illustrated which is suitable for retrofitting an aftermarket spindle lock mechanism 154 to a hand-held power tool 156.
With the exception of the distinctions described herein below, the power tool 156 is similar in all material respects to the hand-held grinder 10 illustrated in FIGS. 1-4 and includes an output collet 158 with a transmission output shaft 160 extending therethrough. A lock pin 162 is disposed within a radial passageway 164 and includes a first, inner end portion 166 which, when the lock pin 162 is displaced inwardly, registers within a locking recess 168 formed in the output shaft 160 to prohibit rotation thereof. When the lock pin 162 is disposed in its outwardmost position (illustrated), the output shaft 160 is free to rotate. The lock pin 162 is continuously urged radially outwardly toward its (illustrated) release position by resilient means such as a compression spring 170 bearing against a step 172 formed within passageway 164 and a stepped collar 174 integrally formed with the lock pin 162. A snap ring 176 disposed within a circumferential recess 178 within passageway 164 defines a stop for the lock pin 162 in the radially outward direction. A second, outer end portion 180 of the lock pin 162 has a flat or slightly crowned upper surface 182 which, when in the released position, extends radially outwardly of the outer opening 184.
A lock lever assembly 186 is affixed to the exterior circumferential surface 188 of the output collet 158 by a retention band 190 including an adjustable cinching mechanism 192. Cinching mechanism 192 can be constructed similarly known automotive hose clamps. The lock lever assembly 186 has an annular base member 194 affixed to retention band 190 and defining a threaded through passage 196 which, when assembled with the power tool 156 registers with passageway 164 along axis X-X. The threaded through passage 196 is dimensioned to enable the outer end portion 180 of the lock pin 162 to freely extend therein. A shaft 198 is threadably engaged within passage 196 of base member 194 whereby a relatively flat thrust surface 200 formed thereby abuts the upper surface 182 of the end portion 180 of the lock pin 162. The outermost end of shaft 198 has a reduced diameter shank portion 202 extending axially outwardly therefrom. An elongated lock lever 204 has a through hole 206 adjacent one end thereof. The shank portion 202 of the shaft 198 is pressed fit within through hole 206 and affixed thereto such as by heading at 208. Thus configured, the lock lever 204 and shaft 198 rotate about axis X-X as a single, unified unit. A torsion spring 210 is disposed concentrically externally of base member 194 and is affixed to the lock lever assembly 186 by a first leg 212 which is grounded within a through hole 214 within retention band 190, and a second leg 216 which is affixed to the lock lever 204 via a through hole 218 therein.
The spindle lock mechanism operates by manual rotation of the lock lever 204 about axis X-X. Rotation of the lock lever 204 rotates the threaded shaft 198, which simultaneously advances the lock lever 204 and shaft 198 axially by virtue of the threaded engagement between the shaft 198 and relatively fixed base member 194. As the shaft advances radially inwardly, its thrust surface 200 bears against the upper surface 182 of the lock pin 162 and advances the lock pin 162 radially inwardly from its illustrated released position into its engaged position. It is envisioned that a relatively course threadform can be employed on the base member 194 and shaft 198 whereby an estimated 180° to 360° degrees of rotation of the lock lever 204 will result in radial inward displacement of the lock pin 162 from the release position to the engaged position. The torsion spring 210 can be selectively pre-loaded to supplement, neutralize or offset the effect of the compression spring 170.
Definitionally, the lock pin 162 and the shaft 198 cooperate to effectively comprise a composite lock pin.
Referring to FIG. 10, an alternative aftermarket spindle lock mechanism 220 is illustrated which can be employed with the power tool 156 of FIG. 9. The spindle lock mechanism 220 includes a retention band 222 which, in application, circumscribes the output collet 158 of the power tool 156. The retention band 222 has an outwardly extending upset portion 224 which forms a hinge point 226 in register with the outer end portion 180 of the lock pin 162 (illustrated in phantom). A lock lever 228 has a handle portion 230 and a cam portion 232. The cam portion 232 is affixed for limited rotation about the hinge point 226 by a hinge pin 234.
The lock lever 228 is releasably retained in the release position by a straddling pair of band lateral guide extensions 236 (only one is illustrated) and a locking tab 238 which engages a recess 239 formed in the handle portion 230. Locking tab 238 is cantilevered from the retention band 222 and resiliently displacable from its illustrated position for releasing the lock lever 228. The cam portion 232 of lock lever 228 defines a contoured caming surface 240 including a minimum radius portion 242, a maximum radius portion 244 and an intermediate radius portion 246. Detent recesses 248 and 250 are formed in the caming surface 240 of lock lever 228 to engage the upper surface 182 of the lock pin 162. Recess 248 is positioned to correspond with the minimum radius portion 242 (release) and recess 250 is positioned to correspond with the intermediate radius portion 246 (engaged) of the lock lever 228. With the exception of the mechanical detents illustrated in FIG. 10, the spindle lock mechanism 220 operates substantially as does the spindle lock mechanism 50 described in connection with FIGS. 1-5.
Referring to FIG. 11, an alternative design for selective engagement of a lock pin 252 and a rotating tool drive element 254 is illustrated. Rather than locking recesses, drive element 254 has a hexagonally configured series of flats 256 formed circumferentially about the circumference of the drive element in register with the lock pin 252. The lock pin 252 has an enlarged inner end portion 258 configured circumferentially arranged flats 260 like an open end wrench which are dimensioned to engage mating flats 256 of the drive element 254 wherever the lock pin 252 is displaced from the released (illustrated) position downwardly to the engaged position.
Referring to FIGS. 12-14, a yet another embodiment of the invention is illustrated which is suitable for retrofitting an aftermarket spindle lock mechanism 262 to a hand-held power tool 264.
With the exception of the distinctions described herein below, the power tool 264 is similar in all material respects to the hand-held tool illustrated in FIG. 9 and includes an output collet 266 with a transmission output shaft 268 extending therethrough. A lock pin 270 is disposed within a radial passageway 272 and includes a first inner end portion 274 which, when the lock pin 270 is displaced inwardly, registers within a locking recess 276 formed in the output shaft 268 to prohibit rotation thereof. When the lock pin 270 is disposed in the outwardmost position (illustrated) the output shaft 268 is free to rotate. The lock pin 270 is illustrated in an intermediate position wherein the inner end portion is at the radial threshold between the engaged and released position. The lock pin 270 is continuously urged toward the release position by a compression spring 278. A second, upper end portion 280 of the lock pin 270 has a crowned upper surface 282 and functions as a cam follower.
A lock lever assembly 284 is affixed to the exterior circumferential surface 286 of the output collet 266 by a retention band 288. An elongated lock lever 290 has a through hole 292 in the center thereof. A retention pin 294 affixes the lock lever 290 to the band 288 while allowing relative rotation about the retention pin 294. The lock lever 290 includes a handle portion 296 and a cam portion 298. The cam portion 298 of the lock lever 290 is sector-shaped at an angle θ (approximately 120°-180°) and defines a constant radius crescent-shaped groove 300 in the bottom surface 301 thereof. As best viewed in FIG. 14, the groove 300 has a bottom surface 302 with a continuously variable depth in the direction of the axis Y-Y of the lock pin 270. The upper surface 282 of the lock pin 270 is urged radially outwardly by the compression spring 278 and is maintained in constant contact with the bottom surface 302 of the groove 300.
The spindle lock mechanism 262 is operated by manually rotating the lock lever 290 from its first end limit of travel wherein the groove 300 has the greatest depth (release position of the lock pin 270) to its second end limit of travel wherein the groove 300 has the least depth (engaged position of the lock pin 300). In FIG. 14, a first phantom lock pin 270′ is illustrated in a first end limit of travel defined by first groove end wall 304. A second phantom lock pin 270″ is also illustrated in a second end limit of travel defined by second groove end wall 306.
It is to be understood that the invention has been described with reference to specific embodiments and variations to provide the features and advantages previously described and that the embodiments are susceptible of modification as will be apparent to those skilled in the art.
Furthermore, it is contemplated that many alternative, common inexpensive materials can be employed to construct the basis constituent components. Accordingly, the forgoing is not to be construed in a limiting sense.
The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used is intended to be in the nature of words of description rather than of limitation.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, the shape of the groove 300 in the embodiment of FIGS. 12-14 is illustrated as having a bottom surface 302 with a constant slope which acts as a ramp against lock pin 270. Alternatively, the bottom 302 could have a contoured or irregular depth, depending on the needs of the user and the configuration of the power tool with which the present invention is being applied. Furthermore, detents (not illustrated) can be implemented within sidewalls of the groove 300 to provide a tactile indication to the operator that the lock lever is at or approaching an end limit of travel (end limits 304 and 306) and restraining the lock lever within each end limit or travel. The detent can be a simple nib integrally formed in a side wall of the groove 300 and directed inwardly to slightly interfere with the lock pin when it passes thereby as it traverses the groove 300. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for illustrative purposes and convenience and are not in any way limiting, the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents, may be practiced otherwise than is specifically described.

Claims

1. A power tool comprising:

a housing assembly;

a motor including a rotating armature shaft disposed within said housing assembly;

a spindle carried externally with said housing assembly for relative rotation about a drive axis;

a drivetrain interconnecting said motor armature shaft and spindle for the application of torque therebetween upon the electrical energization of said motor;

a lock member carried with said housing assembly, said lock member selectively displaceable along a fixed axis between a locked position in which a first end portion of said lock member engages a rotating element of said drivetrain to prevent rotation of said spindle and a released position in which said first end portion of said lock member is spaced from said rotating element to permit rotation of said spindle;

means operative to continuously resiliently urge said lock member toward said released position; and

a lever carried externally of said housing assembly and engaging said lock member, said lever manually operable to displace said lock member from said released position to said locked position.

2. The power tool of claim 1,

wherein said lock member has an elongated cylindrical form with a second end portion opposite said first end portion, said second end portion extending externally of said housing assembly,

wherein said lever is operatively carried with and extends radially outwardly from said second end portion, and

wherein said lock member extends inwardly through a through-bore formed in said housing assembly, said lock member and through-bore defining cooperating helical thread-forms.

3. The power tool of claim 1,

wherein said lock member has an elongated form with a second end portion opposite said first end portion, said second end portion defining a cam-follower surface exposed externally of said housing assembly,

wherein said lock member extends inwardly through a through-bore formed in said housing assembly, and

wherein said lever has a handle portion and a cam portion mounted for limited rotation adjacent an outer surface of said housing assembly whereby said cam portion remains in sliding engagement with said second end portion of said lock member.

4. The power tool of claim 3, wherein said handle and cam portions of said lever are integrally formed in a unified structure.

5. The power tool of claim 4, wherein said lever is mounted for rotation about a hinge pin carried on the external surface of said housing assembly.

6. The power tool of claim 5, further comprising at least one flange member rigidly carried by and extending outwardly from said housing assembly, said flange supporting said hinge pin in a fixed spaced relationship with the housing assembly adjacent to said lock member.

7. The power tool of claim 6, wherein said at least one flange member comprises a pair of spaced flange members, respectively supporting opposed ends of said hinge pin with the cam portion of said lever positionally juxtaposed therebetween.

8. The power tool of claim 7, wherein said pair of spaced flange members are integrally formed with said housing assembly.

9. The power tool of claim 7, wherein said pair of spaced flange members are carried by a support band extending circumferentially about the outer surface of said housing assembly.

10. The power tool of claim 3, wherein said second end portion of said lock member defines a roller-follower.

11. The power tool of claim 3, wherein said lever is elongated and is rotatably displaceable about the cam portion thereof between a stowed orientation substantially parallel to an adjacent outer surface of said housing assembly wherein said lock member is in a released position and a deployed orientation generally normal to the adjacent outer surface of the housing assembly wherein said lock member is in a locked position.

12. The power tool of claim 1, further comprising an operator sensible flag carried on said lever and masking means carried with said housing assembly, said flag and masking means configured and juxtaposed whereby the flag is hidden from view by the masking means when the lever is in said stowed orientation and whereby the flag is visible to the power tool operator when the lever is in said deployed orientation.

13. The power tool of claim 11, further comprising means operative to releasable affix said lever in said released position.

14. The power tool of claim 1, wherein said lever and said housing assembly define cooperating features operative to form a first detent operative to retain said lever in a first end-of-travel position corresponding with the locked position of the lock member, and a second detent operative to retain said lever in a second end-of-travel position corresponding with the released position of the lock member.

15. The power tool of claim 1, wherein said spindle comprises a base portion carried for rotation with said rotating element, and attachment means for alternatively affixing and releasing a rotating tool by the application of torque about said drive axis.

16. The power tool of claim 1, further comprising a control circuit operative to sense the position of the lock member and/or lever and to electrically disable operation of said motor whenever said lock member is in said locked position.

17. The power tool of claim 1, further comprising an outwardly opening recess in said housing assembly to nestingly receive said lever when said lock member is in said released position.