U.S. patent application number 11/879363 was filed with the patent office on 2008-01-17 for power tool with spindle lock.
Invention is credited to James Matthew Pontieri.
Application Number | 20080014844 11/879363 |
Document ID | / |
Family ID | 38949834 |
Filed Date | 2008-01-17 |
United States Patent
Application |
20080014844 |
Kind Code |
A1 |
Pontieri; James Matthew |
January 17, 2008 |
Power tool with spindle lock
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.
Inventors: |
Pontieri; James Matthew;
(Sterling Heights, MI) |
Correspondence
Address: |
J. Gordon Lewis
441 North Evansdale Drive
Bloomfield Hills
MI
48304-3012
US
|
Family ID: |
38949834 |
Appl. No.: |
11/879363 |
Filed: |
July 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60831436 |
Jul 17, 2006 |
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Current U.S.
Class: |
451/359 |
Current CPC
Class: |
B25F 5/001 20130101;
B24B 23/022 20130101 |
Class at
Publication: |
451/359 |
International
Class: |
B24B 27/08 20060101
B24B027/08 |
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.
Description
RELATED APPLICATION
[0001] 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
[0002] 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
[0003] 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.degree.. 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.
[0004] 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.
[0005] 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.degree. 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.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] 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.
[0011] 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.
[0012] 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.
[0013] 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.
[0014] 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
[0015] 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.
[0016] 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
[0017] FIG. 8, is a broken, cross-sectional view of a further
alternative lock member construction including a rotating ball-type
cam follower feature;
[0018] 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;
[0019] 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;
[0020] FIG. 11, is a cross-sectional view of an alternative
"wrench-type" interconnection between the rotating transmission
element and lock member;
[0021] 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;
[0022] FIG. 13, is a bottom side plan view of the lever of FIG. 12;
and
[0023] 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.
[0024] 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
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] 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.
[0030] 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
[0031] The present invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
[0032] FIG. 1, is a side plan view of the preferred embodiment of
the present invention embodied in a hand-held power grinder;
[0033] 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;
[0034] 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;
[0035] 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;
[0036] 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;
[0037] 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;
[0038] FIG. 7, is a broken, cross-sectional view of an alternative
lock member construction including a rotating cylindrical
cam-follower feature;
[0039] 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] The outer end portion 68 of lock pin 58 has a plastic or
nylon button 84 (hereinafter "cam follower") affixed thereto.
[0054] 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.
[0055] The outer opening 72 of passageway 62 opens within an end of
the crescent shaped recess 90 associated with the axle pin 94.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] 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.
[0060] 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.degree. (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.
[0061] 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.degree. 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'').
[0062] 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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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.
[0068] 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.
[0069] 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.
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.degree. to 360.degree.
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.
[0074] Definitionally, the lock pin 162 and the shaft 198 cooperate
to effectively comprise a composite lock pin.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] 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.
[0080] 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 .theta. (approximately
120.degree.-180.degree.) 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.
[0081] 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.
[0082] 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.
[0083] 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.
[0084] 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.
[0085] 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.
* * * * *