Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Docket No. 0186-IR-TH
RATCHET WRENCH
FIELD OF THE INVENTION
This invention pertains to a powered ratchet
wrench for tightening or removing threaded parts~ An
impact clutch mechanism connects the ratchet mechanism
with a rotary power source.
BACKGROUND OF THE INVENTION
Conventional powered ratchet wrenches, such as
that disclosed in Japanese Utility ~odel Ga~ette No.
1976-16,555, have a motor operated by compressed air
in the base of the housing. Nhen a throttle lever is
pressed, compressed air flows to the motor, and the
output shaft of the motor turns a transmission shaft
by way of speed reducing gears. Slow speed and high
torque are transmitted to the transmission shaft. The
eccentric rotation of a crankshaft at the front end of
the transmission shaft oscillates a ratchet yoke. The
movement of the ratchet yoke causes the ratchet
spindle or tool head of a ratchet mechanism to rotate
so that a bolt, nut, or other threaded part is
tightened or removed.
In a conventional ratchet wrench, the gear drive
continues to transmit motor torque directly to the
operator even after the fastener ha~ been tightened to
a specified tightening torque. ~hat is, 1~ khe
throttle lever is held open after the fastener has
been firmly tightened, compressed air continues to
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Docket No. 0186-IR-TH
drive the motor and the gears, which in turn drive
the transmission shaft and ratchet mechanism. Thus, a
considerable reaction force is transmitted to the
operator as the tool tries to rotate around the
tightened, stationary fastener. The operator's hand
can ba je ked forward by the wrench, or the operator
may lose his grip. Even if the operator quickly
releases the lever as soon as tight2ning is finished,
a reaction force is still transmitt2d to khe hand. It
is difficult to prevent the hand ~rom bsing pulled
along or from losing its grip. Hence, the operator
usually releases the lever before tightening is
finished. The operator then turns the tool manually
to finish tightening. The tiyhtening force applied by
these prior art tools can therefore be inconsistentO
In some situations, conventional powered ratchet
wrenches are unsuitable for use in tight places where
there is room for only one hand. Because the ratchet
wrench cannot be gripped tightly in such cramped
places, and since it is dif~icult to release the
throttle lever at exactly the right time, the hand is
often jerked or loses its grip. The operator's hand
can be forcefully thrown against an obstruction and
injured, or the ratchet wrench can forcefully striXe a
projecting part and be damaged.
There is therefore a need ~or a powered ratchet
wrench which minimizes the motor torque reackion ~orce
transmitted to the operator. It is desirable to
provide a powered ratchet wrench which minimizes the
torque reaction force transmitted to the operator's
hand so that the hand is not pulled along with ths
tool while the motor is still operating and torque is
still acting on the fastener.
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SUMMARY OF THE INVF.NTION
In aceordance with -the invention there is
provided a powexed ratchet wrench comprising, in
axial alignment to form an elongated hand]e;
a rotary motor having a rotatahle output shaft;
a rotary impact cluteh meehanism also having a
rotatable output shaft and rotated by the rotatable
output shaft of the rotary motor;
a reversible ratehet mechanism having an
oscillatable ratchet yoke and ls oscillatably driven
through the yoke by ,he output shaft of the impact
clutch; and
a single ended tool dxive spindle is d.riven by
the ratehet mechanism and has i'LS drive axis normal
to the axes of the rotaxy motor and the impact
elutch.
In accordanee with the fuxthex embodiment, thexe
is provided a powexed ratehet wrench compxising:
a rotary motor;
an impact mechanlsm axially allgned with and
engaged with the output shaft of the rotaxy motor,
the impact meehanism further comprising:
a hammex eage in rotaxy dxiven engagement with
the motox output shaft and has at least one hamme.r
jaw;
a rotatable and axially slidable anvil shaft
axially aligned with and eentexed in the hammer eage
and has at least one anvil jaw, one axially extending
anvil eam, and an eceentxic shaft output end;
an impact eluteh means fox causing intexmittent
engagement between the hammer jaw and the anvil jaw
through the eombined aetion of a biasing spring and
the anvil eam to pxoduee xotaxy impacts on the anvil
output shaft; and
a reversible ratehet meehanism having a single
ouput spindle and a yoke in oseillating driven
engagement with the output end of the anvil shaft.
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This invention provides a powered ratched
wrench such -that, when used to tighten or remove a
part or fastener, an impact clut-ch mechanism provldes
the connection between the tool motor and the ratchet
mechanism. To tighten a fastener, the impact clutch
mechanism provides an ini~ial direct connection
between the motor and the ratchet mechanism to se-t or
snug-up the fastener during "run down". The ratchet
mechanism is thereafter rotated by a series of
xotational impac,s delivexed by the impact clutch.
To xemove a fastener, the impacts break the fas-tener
loose, while the direct drive "runs up" the fastener.
If the -throttle lever is not released when fastener
tigh-tening is completed, only minimal torque reaction
foree is transmitted to the operator due to the
impact eluteh. Thus, the tool ean pxefoxm eonsistent
tightening quiekly and reliably, withou~ manual
assistance.
More particularly, the ratehet wreneh aceoxding
to this invention is eonstrueted so that the motor
and ratehet meehanism are eonneeted with an impaet
eluteh rather than a speed xedueing gear deviee, as
in the eonventional wreneh. The impaet clutch allows
the ratehet meehanism to rotate either under direet
motor power or by rotational impaets. An impaet ean
be produeed rapidly and extremely smoothly during
eaeh motor rotation, so that the threaded part ean be
firmly tightened by the ratehet. Thus, while the
ratehet is tightening the part, and after the part is
fully tightened, the eonneetion between the motor and
the ratehet is intermittently broken~ so that the
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Docket No. 0186-IR-TH
ratchet is rotating with minimum reaction to the
operator.
Thus, if the throttle lever is not released when
tightening is completed, only a minimal reac~ion force
is transmitted to the operator. This allows complete
tightening to be carried out consistently and
reliably.
This wrench is also suitable for use in tight
places with room for only one hand on the tool. The
hand won't be thrown against the work piece and
injured, as could happen previously. Also, the danger
of the ratchet wrench striking an obstruction and
being damaged is avoided.
BRIEF_DESCRIPTIONQ F THE DRAWINGS
Figure 1 shows a longitudinal cross section of the
ratchet wrench.
Fi~ure 2 shows a perspective view of the base end
of the anvil shaft, which is an essential part o~ the
invention.
Figure 3 ~hows a aross section along line III-III
of Figure 1, showing the hammer cage and cam ~all o~
the impact clutch mechanism, which constitute
assential parts of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 shows a longitudinal cross section
through a preferred embodiment of the ratchet wrench.
The ratchet wrench 10 is constructed of several
components which will ~irst be described generally. A
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throt-tle lever 20 controls the air flow to a rotary
air motor 30. The rotary output of the motor is
transmit-ted to the hammer assembly 40 of an impact
clutch mechanism. A spring 50 biases an anvil shaft
60 into association with the hammer assembly 40. The
anvil shaft can be directly driven by the mo-tor
through the hammer assembly or can be driven
in-texmittently by a series of rotational impacts from
the hammer assembly. The rotation of the crank on
the anvil causes the reversible ratchet mechanism 70
to reciproca-te or oscillate back and forth, -thus
tightening or removing a th~eaded part of fastener.
Only a small xeaction force is transmitted by the
tool to the operator once the fastener is tight.
More specifically the tool 10 includes a motor
housing 11 and a ratchet housing 12, secured together
in fixed relation such as by a threaded coupling ring
13 and eoupling nuts 14.
A throttle lever 20 opens and closes a throttle
valve 22. When ,hrottle valve 22 is in the open
position, compressed air enters the tool at air inlet
24 which is connected to a suitable compressed air
souree. The eompressed air flows in-to the rotary air
motor 30 and transfers its energy to the rotor. The
spent air is exhausted from exhaust 26.
The rotary motor 30 is located in the motor
housing 11. In the preferred embodiment, an air
motor is shown,. but any rotary power source such as a
hydraulic or electric motor could also be used.
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Docket No. 0186-IR-TH
Air motor 30 has a rotor 3~ and an extending
output shaft 31. The two ends of rotor 34 are
supported by bearings 33 which in turn are supported
by snd plates 32. The rotor is mounted for rotation
in the cylinder 35, the spen ends of whîch are covered
by the end plates 32. The cylinder has an eccentric
bore, as is typical of conventional air motors.
plurality of ~anes 36 are slidably mounted in radial
slots in the rotor. The vanes slide radially back and
forth in the slots as the rotor turns due to
centrifugal force and the eccentric inner surface of
cylinder 35. As the inlet air pushes against vanes
36, it causes rotor 34 to rotate, thus causing output
shaft 31 to rotate therewith.
Numeral 41 designates the hammer cage. It is cup
shaped, having a cylindrical wall portion and a base
portion which together form an inner surface
designated by numeral 44-. Within the hammer cage on
the inner surface 44 are two diametrically opposed
axial grooves. The axial grooves extend only part way
down the cylindrical wall portion, forming
semi-circular shoulders at a specified distance above
the base portion. The hammer cage 41 in this
preferred embodiment is directly driven by the output
shaft 31, as for example by a splined sonnection.
Alternatively, however, the hammer cage could be gear
driven.
Formed in the base portion of the hammer cage is a
circular raceway 47, which is concentric about the
axis of rotation. Coinciding with the raceway, but
extending for only a limited number of degrees, is a
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Docket No. 0186-IR-TH
larger-dimensioned cam ~all pocket ~6. The cam ball
pocket t~pically describes an arc in the range of 45
to 180 degrees. A cam ball 43 is held in the pocket
and rolls freely through the arc.
The anvil shaft 60 carries an axially extending
cam 62. The cam ~2 is preferably a one-sided cam and
projects axially from the end of the anvil shaft. The
cam forms a cam peak with preferably one gradually
rising inclined surface adjacent the cam peak and one
sharply falling surface adjacent the other side of
the peak. The inclined surface occupies about a 90
degree arc on the anvil shaft. The sharp surface
facilitates escape of the cam. The cam 62 and the
raceway 47 are dimensioned so that when the hammer
cage rotates with the cam extending into the raceway,
the hammer cage rotates freely without interference
from the cam. In other words, as the raceway rotates
relative to the cam, the raceway permits the cam to
extend into it without interference.
The anvil shaft carries at least one, and
preferably two anvil jaws 63. The anvil jaws are
diametrically opposed and radially extendingO The
outer radial surfaces o~ the anvil jawc are
dimensioned so that the inner chamber 44 of the hammer
cage can rotate freely about the anvil jaws.
The anvil shaft al50 carries an eccentric crank 61
at the shaft end opposite the cam 62. The anvil shaft
60 is supported by needle bearing 54 so that it slides
~reely in the axial direction as well as freely
rotates. The anvil shaft is also journaled for
rotation and axial movement by a bore in hammer cage
top 42.
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Docket No. 0186-IR-TH
Numeral 50 designates a helical coil biasing
spring of a size to fit around a reduced diameter
portion of the anvil shaft 60 and abut against a
shoulder on the shaft. This biasing spring normally
urges the anvil shaft 60 toward the base portion of
the hammer cage 41, such that the extending cam 62
normally projects into the raceway 47.
At least one, ~nd preferably two hammer jaws 45
are received in the axial grooves of the hammer cage
41. The hammer jaws are harden pins and when in place
are half embedded in the cylindrical wall portion and
half exposed in the inner chamber 44. The hammer jaws
rest on the shoulders of the axial grooves so as not
to extend to the base portion o~ the hammer cage. An
uninterrupted cylindrical surface is provided below
the shoulders at the base of the inner chamber 44.
This surface allows the hammer cage 41 to rotate
relative to the anvil jaws 63 when the biasing spring
urges the anvil shaft toward the base portion of the
hammer cage without impacting on the anvil jaws.
The hammer cage top 42 has a short, snug-fitting,
reduced diameter portion that is inserted into the
inner chamber 44 of the hammer cage. The~cage top
also has two diametrically opposite pilot bores that
axially align with the axial grooves of the ha~mer
cage. The hammer jaws 45 are also received into these
pilot bores to fix the hammer jaws in an axial
position and to lock the hammer cage and hammer cage
top together against relative rotation.
Figure 1 illustrates the ratchet wrench in a
position when the biasing spring 50 is extended and
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Docket No. 0186-IR-TH
the cam 62 is positioned in the raceway 47. The anvil
jaws 63 are biased by the spring toward the base of
the hammer cage such that during rotation of the
hammer cage, the hammer jaws 45 do not intercept the
anvil jaws 63. The uninterrupted cylindrical portion
of the hammer cage 41, that portion located below the
hammer jaws, rotates radially adjacent to the anvil
jaws.
When tha anvil jaws 63 move axially forward, due
to the cam 62 riding up on cam ball 43 and compressing
the biasing spring 50, the orbit of the rotating
hammer jaws 45 intercepts the new position of the
anvil jaws. When the cam ~2 moves the anvil shaft
axially forward during each rotation of the hammer
cage, the hammer jaws 45 produce a series of
rotational impact against the anYil jaws 63.
Eccentric crank 61 is positioned at the end of the
anvil shaft 60 opposite the cam 62. The crank slidas
axially in the bore of a drive bushing 52 so as to
allow for ~he axial movement of the anvil shaft.
Drive bushing 52 slides vertically in a bushing
pocket 72 of ratchet yoke 71 so a~ to accommodate the
up and down movement of the crank 61 as it rotatesO
The oscillating movement of the ratchet yoke is
transferred to the ratchet mechanism 70. The ratchet
mechanism rotates a ratchet spindle or tool head 73 in
a conventional manner as is well known in the prior
art.
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Docket No. 0186~IR-TH
By turning the ratchet reverse knob 74 to the
appropriate setting, the direction of rotation of the
ratchet spindle can be determined. The tool can be
operated to tighten or remove a fastener by setting
the ratchet reverse knob 74.
PERATION
To set a threaded fastener, the ratchet mechanism
is first simply directly driven by the motor through
the impact clutch to rotate or "run down" the fastener
to a snug position. Next, to fully tighten the
fastener, impacts are applied by the impact clutch
mechanism to further rotate the ratchet mechanism and
~urther torque the fastener.
Fiyure 1 illustrates the 'Grun down" position of
the tool. The anvil shaft 60 is in its normal axial
position, that is biased toward the base portion of
the hammer cage with the one-sided cam 62 extending
into the raceway 47. The cam ball 43 is contained in
the limited arc cam ball pock~t 46. When the air
motor rotates, output shaft 31 causes hammer cage 41
to rotate with it due to the splined connection. The
trailing shoulder of the rotating cam ball pocket
engages and drives the cam ball in the direction of
rotation directly of the hammer cage. The cam ball
next engages but does not roll up the inclined surface
of the one-sided cam 62 The rotating cam ball
imparts rotation to the anvil shaft 60. The rotation
of the crank 61 at the end of the anvil shaft causes
the ratchet mechanism to "run down" the ~astener.
Until the ratchet mechanism and the anvil shaft 60
encounter sufficient resistance from the fastener as
it becomes snug, the motor is directly
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Docket No. 0186-IR-TH
driving the ratchet mechanism through the cam ball o~
the impact clutch mechanismO
When the ratchet mechanism and the anvil shaft 60
ancounter sufficient resis~ance, the gradual inclined
surface o~ the cam 62 begins to ride up on the cam
ball 43 due to the continued rotation of the cam ball
with the hammer cage. The anvil shaft and the
attached anvil jaws 63 are moved axially forward away
from the base portion of the hammer cage. In other
words, the cam ball cooperates with the cam to move
the cam and attached anvil shaft axially forward as
the cam rides up on the cam ball as it revolves within
the cam ball pocket and rotates with the hammer cage.
When the cam peak overrides the top of the cam
ball, the cam momentarily maintains its axial momentum
and clears the cam ball, which continues to rotate
beneath the cam. The cam is momentarily in "free
flight" before an impact occurs. There are a few
degrees of clearance between the trailing shoulder of
the cam ball pocket and the hammer jaws. The anvil
jaws 63 have been moved axially away from the hammer
base portion and are now in an axial position which
intercepts the orbit of thP xotating hammer jaws 45.
The exposed portions of the hammer jaws 45 intercept
the new position of the anvil jaws and an impact is
delivered to the anvil jaws.
This impact drives the anvil shaft 60 in the
direction of rotation of the hammer cage until
sufficient resistance is met. This re~istance is the
resistance the fastener encounters as it tightens and
is transferred from the fastener through the ratchet
mechanism to the anvil shaft 60. When sufficient
resistance is met,
Docket No. 0186-IR-TH
the anvil shaft stops rotating and the hammer jaws and
anvil jaws will begin to disengaga.
At that time, the force in the compressed biasing
spring 50 o~ercomes the axial momentum of the anvil
shaft and begins to push the cam back towards the
hammer cage base. As the cam peak moves toward the
base, the steep escape surface adjacent the cam peak
kicks the cam ball in the direction of the leading
edge of the cam ball pocket. The cam peak then again
enters the xaceway 47.
As the hammer cage continues to rotate, the cam 62
once again encounters the cam ball 43. The cam ball
rotates in the cam ball pocket with the cam until the
ball reaches the trailing edge of the pocket. If
there still is sufficient resistance due to fastener
tension, the cam ball will again force the cam to ride
up on the cam ball and the impact sequence will be
repeated until the fastener can not be furthar
tightened. The cam ball thus times the impacts. ~t
ultimate tighening torque, the impact clutch mechanism
will continue to cause the hammer to impact on the
anvil. The ratchet mechanism will not provide any
more tightening torque to the fastener. However, the
tool operator will not experience any torque reaction
due to the tool turning on the tightened fastener.
Rather the operakor will experience only the minimal
reactions due to the impact clutch.
Other emhodiments are considered to be within the
scope of this invention~ For axample, anvil shaft 60
can b~ constructed o~ two pieces to ~acilitate the
manufacture and assembly o~ the tool. A separate cam
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Docket No. 0186 IR-TH
portion having the cam peak and anvil jaws can be
positioned inside the inner chamber 44 of the hammer
cage and splined to a shaft portion extending through
the bore of the hammer cage top. Furthermore, biasing
spring 50 can be positioned anywhere along the shaft
portion of the anvil sha~t 60. For example, in the
embodiment with a two piece anvil shaft, the biasing
spring can be positioned on the splined connection
between the cam portion and the shaft portion
The purpose of the impact clutch mechanism is to
translate rotary motion to interrupted rotaxy motion
having less torque reaction. The impact clutch
mechanism described in connection with the preferred
embodiment can be broadly categorized as a unique
embodiment o~ a cam engage, spring disengage impact
clutch. Other embodiments of the cam engage, spring
disengage type impact clutch are also considered to be
within the scope of this invention. For example, in
the pre~erred embodiment, the anvil shaft moves
axially. An alternate embodiment can provide for the
hammer jaws to move axially rather than the anvil
shaft.
Additionally, other types of impact clutch
mechanisms, such as the cam engage, cam disengage
impact clutch of Mauer (U.S. Patent 3,661,217 issued
May 9, 1972), and the spring engage, spring disengage
impact clutch o~ Pott (U.S.- Patent 3,369,615 issued
February 20, 196~), are considered to be within the
scope of this invention. The Pott impact clutch is
particularly suitable`for electric driven ratchet
wrenches.
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Docket No. 0186-IR-TH
One advantage of this invention over the prior art
includes minimizing the torque reaction to the tool
operator when a fastener is tight and the tool
continues to run. TAis allows the tool to be safely
operated with one hand and also in cunfined and
aw~ard situations. The tool will also produce a
consistent tightening torque. The operator will not
have to stop the tool before the fastener is tight and
manually tighten the fastener out o~ concern for his
own safety and well-being. Additionally, the tool
allows a faster "run-down" of the fasteners than prior
art powered ratchets.
From the foregoing, those skilled in the art will
recognize the improvements over prior art tools and
the considerable advantages.
Changes and modi~ications in the specifically
described embodiments can be carried out without
departing from the SCOpQ of the invention which is
intended to be limited only by the scope o~ the
appended claims.
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