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BACKGROUND OF THE INVENTION
This application is related to applicant's copending U.S. patent
application Ser. No. 08/177,840 entitled FLYWHEEL-DRIVEN FASTENER DRIVING
TOOL AND DRIVE UNIT filed on even date herewith and naming as inventors J.
Crutcher, D. Lucas, D. D'Amico and E. Hunter.
This invention relates to an apparatus for controlling electric motors.
While the invention has many varied applications, it will, for the purpose
of clarity, be described herein as used to control a motor mounted to
drive the flywheel of a fastener applying tool. This description is by way
of example only, and it will be appreciated that the invention has many
varied uses and applications in motor control.
In the past, where relatively large energy impulses are needed to operate a
fastener driving tool (such as a nailer or stapler) for framing purposes,
for example, it has been common to power such tools pneumatically.
Pneumatic fastener driving tools, which require a job site compressor, are
well known. Such tools are capable of driving a nail or staple of 3" or
longer into a framing wood, such as 2.times.4s, for example.
Electrically driven tools, such as solenoid operated fastener driving
tools, are also well known. These are primarily used in lighter duty
applications such as in driving one inch brad nails, for example, rather
than the larger 2" to 4" staples or nails used in framing.
Considerable thought and effort has been expended in providing a heavy
duty, i.e. high powered, fastener driving tools without relying on a
compressor. One alternative approach is employing flywheels as a means to
deliver kinetic energy sufficient to power a heavy duty fastener driver.
Examples of such systems are disclosed in U.S. Pat. Nos. 4,042,036;
4,121,745; 4,204,622 and 4,298,072 and in British Patent No. 2,000,716.
While a great deal of time has been expended in the development of flywheel
driven fastener driving tools, nevertheless, such tools still present
their own unique problems. For example, in tools utilizing two flywheels,
it has been the practice to provide a separate electric motor for each
flywheel. The two motors add considerable weight and bulk to the tool and
are difficult to synchronize. Another approach is to mount one of the
flywheels on the electric motor shaft and then drive the second flywheel
through a series of belts or chains and pulleys. Such drives are complex,
difficult to adjust and are subject to wear.
Another problem area in such tools involves the apparatus to cause one of
the flywheels to move toward and away from the other. Preferably, for
example, a movable flywheel is shifted into an operative position with an
adjacent flywheel wherein its periphery is spaced from the periphery of
the stationary flywheel by a distance less than the nominal thickness of
the thick part of the driver, so to punch and thrust the driver between
the two wheels. The movable flywheel is then shifted in the opposite
direction to an inoperative position wherein its periphery is spaced from
that of the fixed flywheel by a distance greater than the greatest nominal
thickness of the driver, so the drive can be returned for another stroke.
Heretofore, systems to bring about this shifting of one of the flywheels
with respect to the other have been cumbersome, complex and not altogether
satisfactory.
Yet another area of concern in these tools is directed to the means for
returning the driver to its normal, retracted position from the end of the
drive stroke. Complex systems of springs, pulleys and elastomeric cords
have been developed. Such systems, however, have proven to be subject to
wear, stretching and deterioration due to stresses and to lubricants and
foreign materials within the tool housing. Where a spring is used, the
extent of its stroke or travel has been too great, and the spring fails
early, requiring replacement. Other systems have employed a powered return
roller and an idler roller which shifts a free floating driver to its
normal position after the drive stroke. These systems were also found to
be less than satisfactory.
In addition to these concerns, the nature in which such tools are used
presents additional problems when the use of flywheels, as energy devices,
is considered. Specifically, when a flywheel-powered tool is fired or
cycled, energy is transferred from the flywheel to the fastener driver or
ram, for example, for driving a fastener. In essence, the flywheel is
rotated at a speed which provides sufficient rotational inertia such that,
when coupled to the fastener driver, there is sufficient power to drive a
long framing fastener into a target. For example, a typical framing
fastener is about 31/2" to 4" long and may require up to 50 horsepower to
drive it full length into wood.
When a flywheel is used to drive a fastener, the energy used is apparent in
a reduction of the desired initial or starting flywheel speed. That
desired or initial speed must be regained before a fastener driving
operation at the same power can be repeated. The time intervals, however,
needed to accelerate the flywheel back up to the desired or set speed may
lag far behind the frequency with which the user desires to set another
fastener. In other words, physical limitations of the known flywheel
energy systems in such tools limit the frequency or repetition rate with
which they can be used.
While a flywheel energy system might be designed to deliver several energy
impulses of similar power but over increasing time increments, as the
wheel winds down, such functioning as a practical matter is difficult to
control. It is thus desirable to provide a flywheel-operated tool where a
flywheel is accelerated very quickly to its desired or initial speed and
within the time interval required by normal use frequencies.
An associated consideration is that the desired speed to which the flywheel
is accelerated is repeatably and consistently regained and accurately
regulated. Overshoots, undershoots or drifting of the desired speed result
in overpowered or underpowered fastener driving which sets fasteners
either too deeply or not deeply enough.
Another consideration in fastener driving is the variation both in length
or configuration of fasteners and the variation of materials into which
fasteners are driven. It is desirable that a heavy duty fastener driving
tool be adjusted to accommodate such variations, yet at the same time be
capable of quickly and consistently repeating a fastener driving operation
within the selected range of operation.
More specifically, given the mechanical and dimensional specifications of
the flywheel and knowing the driving forces which must be applied by the
tool, the range of required angular speeds of the flywheel can be
determined. In order to achieve the necessary consistency and
repeatability of the driving action without overdriving or underdriving
the fastener, the speed of the electric motor connected to the flywheel
must be regulated within .+-.1%. A typical selectable range of angular
velocities of the motor required by the range of driving forces, is from
7,000 revolutions per minute (rpm) to 15,000 rpm, when used with
flywheels, for example, weighing 0.87 pounds and having a movement of
inertia of 4.016.times.10.sup.-4 ft. -lbs.sec.sup.2. Further, when the
tool drives a fastener, the kinetic energy is expended and the speed of
the flywheel is reduced. The motor must be accelerated back to the
selected speed within 500 milliseconds. It is also necessary that the
motor and its control be immune from a high noise environment, for
example, both radiant and power line noise may be created by other high
power equipment and brush noise within the motor itself. In addition, the
driving tool is often used in environments of temporary power hook ups in
which significant voltage fluctuations are frequent and severe. The motor
and its control must have minimum weight and cost in order to be
commercially viable in a portable hand-held tool.
It is known that there are currently many motor speed controls for
different types of motors. For example, a Motorola TDA 1085C is an
integrated circuit component providing a universal motor speed control
which uses triac phase angle control with a voltage comparison velocity
feedback loop. There are many references to motor speed controls utilizing
phase locked loops primarily for the control of brushless DC motors. The
theory and feasibility of using a phase locked loop in the control of
universal AC/DC motors in lieu of phase angle control is also known.
Further, there are existing portable hand held tools in which speeds are
selectable. However, those systems typically are open loop in nature and
do not require a precise closed loop speed control. Such open loop speed
control systems may be obtained by switching power to the motor between a
half wave and a full wave power supply or switching selected motor coils
into and out of the circuit or by mechanical gearing. Further, portable
hand held tools which are battery powered typically pulse width modulate
current to a permanent magnet field coil motor.
None of such known circuits are capable of providing a speed control for a
universal AC/DC motor useful in a hand-held portable device with the speed
range, precision and response time requirements of the present invention.
Consequently, heretofore there has not been available in the industry a
reliable, lightweight and relatively simple electromechanical fastener
driving tool which can efficiently, consistently and repeatably drive
fasteners of various sizes, and particularly those sizes needed in heavy
duty framing applications.
A further consideration with electric tools, particularly with
flywheel-operated or other hand tools, is the weight and expense of the
drive unit. Motors with sophisticated speed controls can be very heavy and
expensive. It is thus desirable to provide fastener driving tools or drive
units for tools, implements or other devices with relatively lightweight,
speed controlled motors at a relatively low cost.
With hand-held or hand-operated tools, it is desirable not only to provide
a relatively lightweight energy source, but to provide a tool or implement
which is balanced. In the prior application identified above, a fastener
driving tool is powered by a flywheel driven by a motor, where both
flywheel and motor are located in the forward end of the tool. The center
of gravity of such a device is forward, and it is difficult to balance the
tool. On the Other hand, moving the motor away from the flywheel requires
a coupling or extended drive which increases tool weight, and drains
effective power. This may require a larger motor with the attendant weight
increases. It is thus desirable to provide an improved, well-balanced
hand-held fastener driving tool, and a drive unit facilitating the balance
of such hand-held tools.
While the noted considerations are important to fastener tools and their
particular application, the operation of many tools, implements and
devices requires the application of a motive force or energy pulse to a
working member. Many such apparatus require only a short or limited motion
of such an implement or member to accomplish a task. Currently, in
addition to the flywheel and pneumatic systems noted above, such apparatus
are powered electrically, or hydraulically, by motors or solenoids, for
example, by internal combustion devices, springs or other devices. By way
of example only, devices other than fastener driving tools which require
or utilize various energy sources to move a working member include: paper
punches, diverse material punchers, shears, cutters, pruners, wrenches,
stitchers, riveters, pulverizers, tampers, aerators, slippers, chisels,
material handling devices, hammers, hammer drills, embossers, pumps,
coining devices, clamps, and tools or implements for many other
applications. It is desirable to provide an improved drive or power unit
for such tools.
One object of the invention is to provide a low cost, reliable and light
weight motor control which provides accurate speed control for a motor.
A further objective of the invention is to provide a motor control having a
wide range of motor speeds selectable by an operator and the capability of
automatically and rapidly accelerating back to a selected speed after a
loss of speed caused by the imposition of a load on the motor.
A further objective of the invention to provide an improved apparatus for
delivery of an energy pulse to a working member.
A further objective of the invention has been to provide an improved
apparatus for delivering an energy pulse from a flywheel to a fastener
driver or to the working member of a tool or implement.
A further objective of the invention has been to provide a motive apparatus
and a control therefor for driving a flywheel at a selected speed, and for
regaining that speed quickly after a speed reduction.
A further objective of the invention has been to provide an improved
flywheel-driven fastener driver capable of producing desired energy pulses
at desired cycle frequencies.
A further objective of the invention has been to provide an improved
portable hand-held power tool.
To these ends, one preferred embodiment of the invention comprises a power
or drive unit in operative disposition in a fastener driving tool. A
flywheel is mounted in a tool housing and a handle extends rearwardly from
the housing with a motor for driving the flywheel being mounted at a
distal end of the housing. A drive shaft coupled to the motor has a pinion
with spiral bevel gear teeth meshing with similar teeth on the flywheel.
The motor weight at the handle's rear end tends to balance out the tool
housing and its components so the entire tool feels balanced.
A drum is mounted in the housing. It includes a first circumferential
surface. A first drive cable is secured to the drum so as to be wound up
on the surface when the drum rotates. A cone clutch is utilized to
selectively and intermittently interconnect the flywheel to the drum to
impart a pulse of energy to the drum to rotate it and wind up the cable
onto the drum. The other end of the cable is attached to a fastener
driver. When the drum is rotated, the cable is wrapped onto the drum, and
pulls the driver to engage and drive a fastener. The energy stored in the
flywheel is thus delivered to the fastener through the drum, cable and
fastener driver.
Another or a second circumferential surface, having a diameter preferably
smaller than the first circumferential surface, is operatively secured to
the drum. A second, or return, cable is attached to the second surface and
is wound thereabout when the drum is rotated by the flywheel. The other
end of the second return cable is attached to a coil spring which is
compressed when the return cable is wound up. After the clutch disengages
the drum from the flywheel, this spring expands to tension the second
return cable, reversing the drum and pushing the first cable and fastener
driver back to a start position. Since the return cable wind-up surface is
of less diameter than the drive cable surface, the second return cable
does not traverse so much distance as the drive cable when the drum is
actuated by the flywheel and clutch. The spring travel is thus held within
a range which does not unduly stress or fatigue the spring despite
extensive cycling of the tool.
Trigger actuated linkage and an axially expansible actuator serve to
actuate the clutch to momentarily interconnect the flywheel to the drum.
The actuator is similar in structure and operation to the prior
application incorporated by reference herein.
An relatively simple and inexpensive AC/DC motor is used. A control
operates the motor at a selected speed depending on fastener length and
configuration and on target parameters. The control serves to accelerate
the motor, and the flywheel back to an initial speed with only a very
short delay of about 500 milliseconds; well within the period of the
desired frequency of use.
The speed of the universal AC/DC motor is controlled by switching the phase
angle of an AC signal with a triac power switch in response to a motor
control providing phase-locked loop velocity control. The triac power
switch is connected between the source of AC power and the motor and has a
trigger input for controlling the application of the AC signal to the
motor. An analog reference circuit is responsive to the AC signal and
initiates a ramp signal with each zero crossing of the AC signal. The ramp
signal has a duration approximately equal to the duration between zero
crossings of the AC signal.
A speed command circuit provides a speed command signal having a reference
frequency representing one of several selectable desired speeds of the
motor. A feedback circuit is responsive to rotation of the motor and
produces a feedback signal having a feedback frequency representing the
actual speed of the motor. A phase detector produces an error signal
representing the phase difference between the speed command and the
feedback signals which is averaged by a low pass filter. A comparator
produces a trigger pulse to the triac power switch during each occurrence
of the ramp signal as a function of the detected phase difference, The
leading edge of the trigger pulse occurs at a time during the ramp signal
that is determined by the phase difference between the reference and
feedback frequencies. The trigger pulse switches the triac as a function
of that phase difference, and the AC signal is applied to the motor to
lock the phase of the speed command and feedback signals thereby
maintaining the actual motor speed equal to the desired motor speed.
A fastener driving tool embodying the invention may also include a fastener
magazine which is not only inclined, but curved, and which extends
rearwardly toward the motor on the handle's rear end, from a forward
position below the driver, partially encircling the handle, and helping
balance the tool.
The power or drive unit such as described can be used with various tools,
implements or other devices to impart a pulse of energy to a movable or
working member thereof. Such a unit includes the motor, motor control
driveshaft, flywheel, drum, drive and return cables, clutch trigger
linkage, and clutch actuator. Where the balance and/or portability is of
no concern, the motor may be mounted to directly drive the flywheel. A
hand tool embodying the invention may also include a tool housing, a
handle extending therefrom, a motor in a distal end of the handle and a
shaft through the handle coupling the motor to a flywheel in the housing,
together with a control for accelerating the motor and flywheel to
predetermined speeds in a minimum time period.
The present invention has the advantage of providing very accurate speed
control of the motor and a very fast response to speed deviations from a
selected speed. A further advantage is realized because the frequencies of
the speed command and feedback signals are less susceptible to noise. A
further advantage is that the above features are provided by a low cost,
light weight and reliable motor control.
These and other objectives and advantages will become readily apparent from
the following detailed description of the invention, and from the drawings
in which:
FIG. 1 is a side elevation view of a fastener driving tool embodying the
invention;
FIG. 2 is a front elevation view of the tool of FIG. 1 in partial
cross-section taken along line 2--2 of FIG. 1, taken generally on line
3--3 of FIG. 2;
FIG. 3 is an enlarged side view in partial cross-section of the tool of
FIG. 1, taken generally on line 3A--3A of FIG. 2;
FIG. 3A is an enlarged view in cross-section of the other side of the tool
of FIG. 1;
FIG. 4 is a cross-sectional view taken along lines 4--4 of FIG. 1, showing
the tool in an unfired condition;
FIG. 4A is a cross-sectional view like FIG. 4 taken along lines 4A--4A of
FIG. 1 showing the tool just as the clutch is initially engaged;
FIG. 5 is a cross sectional view taken along lines 5--5 of FIG. 4;
FIG. 5A is a cross sectional view taken along lines 5A--5A of FIG. 4A, but
illustrating the tool after clutch engagement in a fully fired condition;
FIG. 6 is an exploded view of the flywheel, drum, clutch, actuator
components and trigger linkages of the tool of FIG. 1;
FIG. 7 is an expanded and enlarged view of actuator components of the tool
of FIG. 1;
FIGS. 8A-8E are illustrations of operating sequences of the components of
the tool of FIG. 1 where the trigger is first engaged and the work
contacting element ("WCE") is then brought into contact with the target to
cycle the tool;
FIGS. 9A-9C are illustrations of operating sequences of the components of
the tool of FIG. 1 when the WCE is first engaged and thereafter the
trigger is engaged to cycle the tool;
FIG. 10 is a schematic block diagram of the motor control of the present
invention; and
FIG. 11 is a circuit diagram illustrating components of the motor control
of FIG. 10 in more detail.
MECHANICAL STRUCTURE
Turning now to the drawings, there is illustrated in the Figures a
preferred embodiment of the invention in the form of a fastener driving
tool 10 for driving fasteners such as nail "N" (FIG. 5A) into 2.times.4s
"W" (FIG. 5A). It will be appreciated that the preferred embodiment of the
invention includes a motor control which can be used with motors of a
variety of tools or implements having working elements or members which
must be powered to move through a stroke, such as, for example, the driver
of tool 10. The tool 10, however, includes a housing 11, a handle 12
having a forward end 13 and a rearward end 14 and a magazine 15. The
magazine 15 is mounted to the rear end 14 of handle 12 and to the forward
end 17 of the tool housing 11 by a bracket 19. Bracket 16 serves as a foot
for supporting the tool in an upright position when set on a horizontal
surface.
In FIG. 2, the magazine 15 is shown in more detail. It will be appreciated
that the magazine is curved from front to back and is also inclined. A
forward end of the magazine is interconnected with the nose piece 18 of
the tool, by means of a bracket 19. The magazine is operable through this
interconnection to deliver fasteners, one after the other, to a position
or driving station in the nose piece area from which the fasteners can be
driven upon cycling or operation of the tool. Fasteners are delivered from
the magazine seriatim to the driving station at the end of the driver for
driving into a target.
It will be appreciated that the curved configuration of the magazine
extends the magazine outwardly around the left side of the handle 12. The
handle can still be grasped in either the right or the left hand of the
user.
Returning to FIG. 1, it will be appreciated that a motor "M" is located in
the rear end 14 of the handle 12 and is connected by an appropriate wires,
such as shown at 20, to a source of electricity for running the motor. A
speed display and a thumbwheel or other motor speed selector is located on
the housing 11 in the general area designated by the numeral 21, so that a
user of the tool can select a predetermined speed, depending on the length
and configuration of the fastener to be driven and the parameters of the
target into which it is to be driven.
Of course, the magazine 15 is spring biased to urge fasteners, such as
nails or staples, serially one after the other, toward and into position
at the nose piece 18 for driving by the tool's driver.
As noted herein and as will be explained in detail, the tool is energized
by a rotating flywheel, not shown in FIG. 1, which is driven by the motor
"M" at the rear end 14 of the handle 12. A driveshaft 22 is interconnected
between the motor and the flywheel for purposes of rotating the flywheel
when the motor is electrically driven. The driveshaft 22 extends through
the handle 12 from the motor "M" at the rear end 14, through the front end
13 of the handle, and to the flywheel mounted in the housing 11, as will
be further described.
Turning now to FIG. 3, there is shown in partial cross-section, certain of
the interior components of the tool. These include a pinion 25 secured to
the end of bearing-supported driveshaft 22. The pinion 25 is provided with
spiral bevel gear teeth 26. Pinion 25 is mounted so that the teeth 26
intermesh with corresponding spiral bevel gear teeth 27 on a flywheel 30,
mounted for rotation on an axis 31. The tool 10 also includes a preferably
mechanical trigger 35, which may be depressed in the direction of the
arrow shown in FIG. 3 to actuate or cycle the tool 10. It will be
appreciated that the motor at the rear end 14 of the handle 12, when
energized, constantly drives the driveshaft 22 and the pinion 25, which
spins the flywheel 30 in a clockwise direction as viewed in FIG. 3. The
motor is thus directly coupled to the flywheel.
Turning now to FIGS. 5 and 5A, and as partially seen in FIGS. 4 and 4A, the
tool 10 further includes a fastener driver 40 mounted for reciprocation in
a vertically disposed tube 41 at the forward end of the housing 11. The
elongated driver 40 may be of any suitable shape, such as a round rod or
bolt, or a rounded rod generally "C"-shaped or "D"-shaped in cross-section
similarly to the head of a fastener to be driven; or the fastener driver
40 may be flattened and rectangular in cross-section, or of any other
suitable configuration. The tool further includes a stop 43 for the driver
40 and the coupling 42 (FIG. 2). The driver 40 extends from an attached
coupling 42 at the upper end thereof.
A drive cable 45 is attached to the coupling 42 at an upper end 46 of the
cable. The cable preferably is a flat ribbon comprising a multiplicity of
strands bound in a plastic or synthetic material. Such a cable is
available from the Orscheln Company, Moberly, Mo. The other lower end 47
of the cable is attached to the apparatus for driving the driver, as will
be described.
The tool housing 11 further includes a sleeve 49 housing a return spring
50. An endcap 51 is connected to an upper end of the spring 50 and a
return cable 52 is connected at its upper end to endcap 51. A lower end 53
of cable 52 is also interconnected with the driving apparatus to turn that
apparatus to a prefired condition, as will be described.
Turning now momentarily to FIG. 6, there is shown therein, mounted on axis
31, a plurality of operational parts for the tool. Beginning with the
flywheel 30 at the lefthand side of FIG. 6, there is shown in FIG. 6 a
cone clutch member 55, a drum stop 56, a drum 57, an inner ball plate 58,
a bearing cage 59, an outer ball plate 60, thrust bearing 61, a spacer
washer 62, belleville springs 63 and a ratchet ring 64. While FIG. 6 shows
these various elements in an expanded form, they are assembled on the axis
31, as perhaps best seen in FIGS. 4 and 4A, while details of the inner and
outer ball plates 58 and 60 are also seen in FIG. 7.
With respect then to FIGS. 4, 4A, 6 and 7, it will be appreciated that the
flywheel 30 is driven via the spiral bevel gears 27. The flywheel has a
frusto-conical surface 66 (FIG. 4A) for receiving the cone clutch 55, and
is mounted on an axle 67 by means of bearings 68 for free rotation about
axis 31. The cone clutch includes a frusto-conical surface 70, faced with
frictional clutch material 71. When the cone clutch 55 is pressed into the
flywheel 30, the frictional material 71 engages the surface 66 in the
flywheel so that the flywheel drives or rotates the cone clutch.
As perhaps best seen in FIGS. 4 and 4A, the inner ball plate 58 includes a
tubular projection 73, which is provided with splines 74 (FIG. 6). This
projection 73 with its inner ball plate 58 is mounted on axle 67 for
rotation with respect thereto by means of a sleeve 75. The cone clutch 55
is provided with a plurality of internal splines 76, which intermesh with
the splines 74 of the inner ball plate 58, so that the cone clutch 55 is
mounted over the projection 73 in non-rotating relationship with respect
thereto. The cone clutch 55 is maintained on the projection 73 by means of
a snap ring 77. A spring 79 is mounted on axle 67 between the sleeve 75
and inner ball plate 58 on the one end, and a snap ring or retainer 80 on
the other end, so that the cone clutch 55 and inner ball plate 58 are
biased in an axial direction along axis 31, away from the flywheel 30 by
spring 79. Drum 57 includes internal splines 81 and is also mounted on
splines 74 of projection 73 extending from the inner ball plate 58 for
rotation therewith. Drum 57 includes a circumferential cable receiving or
wind up surface 82 for receiving drive cable 45.
Inner ball plate 58 is also provided with a projection or boss 85, defining
a circumferential or cylindrical surface 86 for receiving and winding up
the return cable 52. The diameter and circumference of cylindrical wind-up
surface 86 is less than that of wind-up surface 82.
It will thus be appreciated from the description so far that when the cone
clutch 55 is rotated by the flywheel 30, this engagement also drives the
inner ball plate 58 and the drum 57, thereby winding up cable 45 on
wind-up surface 82 of drum 57, and winding up cable 52 on surface 86 of
the inner ball plate 58.
As illustrated in FIGS. 4 and 4A, and as further illustrated in FIG. 7,
three ball bearings 88 reside in pockets 89, 90 and 91 in inner ball plate
58 and in corresponding pockets 92, 93 and 94, in outer ball plate 60. Of
course, only one ball is shown in each of FIGS. 4 and 4A, in view of the
sectioning of the drawings, and for clarity. As seen in FIG. 7, each of
the pockets 89, 90 and 91 have a trailing ramp 95, 96, 97 respectively,
each of which are inclined up to a respective race surface 98, 99, 100. As
shown in FIG. 7, the pockets 92-94 of the outer ball plate 60 also have
associated ramps 101, 102 and 103 tapered upwardly from the bottom of the
pocket to respective races 104, 105 and 106. The inner ball plate
comprises a concave-like shield 109. The outer ball plate 60 includes a
boss-like projection 111 which has three dogs 112, 113 and 114 projecting
radially from a circumferential surface 115 thereof. Moreover, the outer
ball plate 60 also includes a plurality of teeth 117 projecting radially
from an outer periphery of the plate.
When the respective pockets of the inner and outer ball plates 58, 60 are
aligned, the ball bearings 88 therein are received within the pockets, so
that the outer and inner ball plates are positioned relatively close
together, as shown in FIG. 4, with the bearings 88 retained in cage 59. On
the other hand, when the outer and inner ball plates 58 and 60 are rotated
relative to each other, the resulting motion of the balls forces the two
members apart, as will be further described.
As shown in FIG. 4A, when the plates 58 and 60 are forced apart, this
action tends to both compress the belleville springs 63 and the spring 79
on the other side of the cone clutch 55, driving the cone clutch 55 into
engagement with the flywheel 30, for the purpose of resulting in rotation
of the inner ball plate 58 and the drum 57 by the flywheel 30, as will be
described.
Returning now momentarily to FIG. 6, ratchet ring 64 is disposed on axis 31
closely adjacent the outer ball plate 60. When the tool is in the
condition shown in FIG. 4, the outer ball plate 60 does not reside within
the ratchet ring 64 and is not affected by that ratchet ring. In this
position, the belleville springs 63 maintain the outer ball plate 60 away
from the ratchet ring 64 in an axial direction. When, however, the ball
bearings 88 force the inner and outer ball plates 58, 60 apart, the outer
ball plate 60 moves axially toward and into the ratchet ring 64 so that
the teeth 117 engage the internal teeth 118 of the ratchet ring 64 to
prevent r | | |
