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Patent 1125593 Summary

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Claims and Abstract availability

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(12) Patent: (11) CA 1125593
(21) Application Number: 1125593
(54) English Title: SPEED RESPONSIVE MOTOR SHUTOFF MECHANISM FOR FLUID OPERATED TOOL
(54) French Title: MECANISME DE COUPURE REAGISSANT AU REGIME MOTEUR POUR OUTIL COMMANDE PAR FLUIDE
Status: Term Expired - Post Grant
Bibliographic Data
(51) International Patent Classification (IPC):
  • B23P 19/06 (2006.01)
  • B25B 23/145 (2006.01)
  • F01C 13/02 (2006.01)
(72) Inventors :
  • WORKMAN, WILLIAM, JR. (United States of America)
(73) Owners :
  • COOPER INDUSTRIES, INC.
(71) Applicants :
  • COOPER INDUSTRIES, INC. (United States of America)
(74) Agent: GOWLING WLG (CANADA) LLP
(74) Associate agent:
(45) Issued: 1982-06-15
(22) Filed Date: 1979-10-12
Availability of licence: N/A
Dedicated to the Public: N/A
(25) Language of filing: English

Patent Cooperation Treaty (PCT): No

(30) Application Priority Data:
Application No. Country/Territory Date
013,486 (United States of America) 1979-02-21

Abstracts

English Abstract


ABSTRACT OF THE DISCLOSURE
A portable pneumatic tool includes a valve closure member
interposed in the tool motor exhaust passage and engaged with
a speed responsive mechanism comprising a plurality of flyweights
operable to move the closure member to an open position on starting
of the tool motor. On decreasing motor speed a coil spring
assisted by a fluid pressure drop across the closure member
forces the closure member to move against the decreasing centri-
fugal force exerted by the flyweights to shut off-motor exhaust
fluid flow to stop the motor. The closure member is normally
held in a partially open position by a second spring to enable
the motor to be started.
-10-


Claims

Note: Claims are shown in the official language in which they were submitted.


The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. In a fluid operated tool for tightening threaded fasteners
and the like:
a housing;
a fluid operated motor disposed in said housing;
means forming a fluid exhaust passage in said housing
for conducting exhaust fluid away from said motor to the exterior
of said housing;
a valve closure member operable to be in an open position
to permit exhaust fluid flow through said exhaust passage and a
closed position blocking the flow of exhaust fluid through said
exhaust passage to stop said motor;
a member engaged with said motor and operable to be
rotatably driven by said motor;
flyweight means engaged with said member and responsive
to starting of said motor to move said closure member to a
substantially full open position to permit the flow of exhaust
fluid through said exhaust passage; and
means responsive to decreasing motor speed to cause said
closure member to move to said closed position.
2. The invention set forth in Claim 1 together with:
first spring means for biasing said closure member to
move toward a closed position in response to a decreasing centri-
fugal force on said flyweight means caused by the speed of said
motor decreasing below a predetermined minimum.
3. The invention set forth in Claim 2 together with:
second spring means for biasing said closure member
to a partially open position to permit an initial flow of exhaust
fluid from said motor upon starting said motor.
4. The invention set forth in Claim 3 together with:
a motive fluid shutoff valve interposed in a motive
fluid supply passage leading to said motor, said motive fluid
shutoff valve being operable in its motive fluid shutoff
position to vent pressure fluid from said motor and said exhaust
passage between said motor and said closure member.
5. The invention set forth in Claim 3 wherein:
said member drivably engaged with said motor includes a
plurality of substantially radially extending grooves, said
grooves having respective inclined bottom surfaces, and said
flyweight means comprises a plurality of spherical balls disposed
one in each of said respective grooves and operable in response
to centrifugal forces acting thereon to move radially outwardly
in said grooves to cause said closure member to move to a
fully open position.

6. The invention set forth in Claim 5 wherein:
said means responsive to decreasing motor speed
includes a plate interposed between said closure member
and said balls and engageable with said balls, and said
second spring means includes a spring washer interposed
between and engaged with said plate and said closure
member.
7. The invention set forth in Claim 2 wherein:
said housing includes first and second interior chambers
forming at least part of said exhaust passage, a transverse
wall surface in said first chamber forming a valve seat en-
gageable by said closure member for shutting off the flow of
exhaust fluid from said first chamber to said second chamber.
8. The invention set forth in Claim 7 wherein:
said closure member includes a pressure surface responsive
to an increase in the exhaust fluid pressure in said first
chamber when said closure member moves toward the valve closed
position to assist said first spring means in biasing said
closure member to engagement with said valve seat.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY
DISCLOSURE
9. The invention set forth in Claim 1 together with:
a limited motion coupling drivably interconnecting
said motor and said closure member and operable to urge said
closure member to move toward a closed position in response
to a decreasing centrifugal force on said flyweight means
caused by the speed of said motor decreasing below a
predetermined minimum.
10. The invention set forth in Claim 9 wherein:
said coupling includes a coupling member drivably
connected to said motor and to said closure member and opera-
ble in response to increasing motor speed to permit said fly-
weights to move said closure member to said open position.
11. The invention set forth in Claim 10 wherein:
said coupling member includes a journal portion, said
closure member is disposed on said journal portion and said
coupling includes means forming a driving connection between
said coupling member and said closure member which provides
for limited axial and rotational movement of said closure
member with respect to said coupling member.
12. The invention set forth in Claim 11 wherein:
said means includes spiral groove means on one of said
members and key means engaged with the other of said members
and extending into said groove means.
13. The invention set forth in Claim 12 together with:
spring means for biasing said closure member to a
partially open position to permit an initial flow of exhaust
fluid from said motor upon starting said motor.
14. The invention set forth in Claim 13 together with:
a motive fluid shutoff valve interposed in a motive
fluid supply passage leading to said motor, said motive fluid
shutoff valve being operable in its motive fluid shutoff posi-
tion to vent pressure fluid from said motor and said exhaust
passage between said motor and said closure member.
15. The invention set forth in Claim 13 wherein:
said member drivably engaged with said motor includes
a plurality of substantially radially extending grooves, said
grooves having respective inclined bottom surfaces, and said
flyweights comprise a plurality of spherical balls disposed
one in each of said respective grooves and operable in response
to centrifugal forces acting thereon to move radially outward
in said grooves to cause said closure member to move to a fully
open position.
11

16. The invention set forth in Claim 15 wherein:
said means responsive to decreasing motor speed includes
a plate interposed between said closure member and said balls
and engageable with said balls, and said spring means includes
a spring washer interposed between and engaged with said plate
and said closure member.
17. The invention set forth in Claim 2 wherein:
said housing includes first and second interior chambers
forming at least part of said exhaust passage, transverse wall
surface in said first chamber forming a valve seat engageable
by said closure member for shutting off the flow of exhaust
fluid from said first chamber to said second chamber.
12

Description

Note: Descriptions are shown in the official language in which they were submitted.


SPEED RESPONSIVE MOTOR SHUTOFF MECHANISM
FOR FLUID OPERAI'ED TOOL
BACKGROUND OF THE INVENTION
This invention pertains to a speed responsive shutoff
mechanism for a pneumatic nut running-tool wherein the motor
exhaust flow is interrupted at a predetermined minimum speed
of the tool motor as the motor approaches the stall condition.
In the art of control devices for pneumatic power tools,
in particular nutsetters, screwdrivers and the like, there have
been a number of inventions dealing with a speed responsive valve
for shutting off the motor inlet air flow when the motor speed
approaches the stall condition. U.S. Patents 3,904,305; 4,004,859
10 and 4,120,604 disclose pneumatic tools which include speed res-
ponsive valve mechanisms for shutting off fluid flow to the motor
inlet port when the motor approaches the stall condition from a
relatively high speed operating condition. U.S. Patents 3,785,442;
3,791,458 and 3,850,553 disclose speed responsive devices which
generate a pressure fluid signal at a predetermined minimum speed
of the tool motor to cause a servo-operated valve to shut off
motive fluid flow.
A common disadvantage of the devices disclosed in the first
three patents abovementioned is that although the speed responsive
devices operate to shut off direbtly the fluid flow to the motor
inlet port, these devices all require a so-called bypass valve
for providing motive air to start the motor so that the respective
centrifugal force responsive mechanisms can open a motor inlet
fluid passage which is then reclosed on decreasing motor speed.
The three last mentioned patents also disclose somewhat com-
plicated mechanisms which require speed responsive valve devices
that provide a pressure fluid signal for operating separate motive
fluid shutoff valves.
- 1 -

112~;i5~3
SUMMARY OF THE INVENTION
The present invention provides for a speed responsive motive
fluid shutoff device for a fluid operated tool such as a pneumatic
nutsetter or the like which operates to shut off the motive fluid
exhaust flow from the tool motor in response to decreasing motor
speed. Accordingly, the shutoff -device according to the present
invention may be used to control the maximum torque exerted by
the tool on a driven fastener. The motor shutoff mechanism of
the present invention also functions to indicate that the tool
motor speed has decreased to a predetermined minimum on approach-
ing a stalled condition. Moreover, the motor shutoff mechanismin accordance with the present invention is designed to minimize
.,
the torque reaction imposed on the tool operator as the tool
motor approaches the stalled high output torque condition.
~The speed responsive motor exhaust flow shutoff valve is
particularly advantageous in that a disc or plate type valve
closure member is arranged in the motor exhaust fluid flow path
and is actuated substantially directly by a speed responsive
flyweight mechanism. Moreover, the motor exhaust flow shutoff
valve does not require a bypass valve for providing motive fluid
to start the tool motor as with prior art mechanisms.
Accordingly, the speed responsive motor shutoff mechanism
of the present invention is compact, mechanically simple, less
complicated, and less expensive than heretofore known speed res-
ponsive motor shutoff devices for fluid operated tools.
BRIEF DESCRIPTION OF THE DRAWING
Fig. 1 is a longitudinal side elevation of a portable pneu-
matic tool which includes the speed responsive motor shutoff
mechanism of the present invention;
Fig. 2 is a longitudinal center section of the speed respon-
sive motor shutoff mechanism embodied in the tool shown in Fig. l;
and,
--2--

1~4'~S~
Fig. 3 is a section view taken along the line 3-3 of
Fig. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Fig. 1 of the drawing the speed responsive
motor shutoff mechan-ism of the present invention is adapted,to
be used in a portable pneumatic tool gene~ally designated by the
numeral 10 and comprising a nutsetter. The tool 10 includes a
housing portion 12 in which is disposed a conventional rotary
vane type expansible chamber motor 14. Motive fluid such as
compressed air is supplied to the tool by way of a flexible
conduit 16 connected to the tool handle 18. A manually actuated
shutoff valve 20,shown schematically in Fig. 1, is operable to
control the supply of pressure fluid to the motor by way of
passage 22. The valve 20 is shown schematically in Fig. 1 for
clarity and is adapted to be disposed in the tool housing and to
be actuated by a suitable operating lever 24. The tool 10 also
includes a housing portion 26 which includes a drive shaft 28
suitably connected to a socket member 30 for driving a threaded
fastener or the like in a known way.
The tool 10 further includes a housing portion 32 intermediate
the housing portions 12 and 26 and suitably secured thereto by
respective threaded collars 34 and 36. Referring to Fig. 2, the
housing portion 32 is adapted to have interior chambers 38 and
40 which may be in fluid conducting communication with each other
to form passage means for the exhaust fluid flow from the motor
14. Exhaust fluid from the motor 14 is conducted to the chamber
38 through motor exhaust port means 42 in the motor end plate 44.
Exhaust fluid flows from the chamber 40 through the hollow interior
of the housing portion 26 and exits from the tool through suitable
louvers 46, shown in Fig. 1.
Referring again to Fig. 2, the motor 14 includes a rotor 48
having an output shaft portion 50 which is drivably coupled to

S5~
an intermediate drive shaft 52. The drive shaft 52 is rotatablY
supported in the housing portion 32 and includes a portion forming
the sun gear 54 of a planetary gear drive. The planetary gear
drive includes a planet gear carrier 56 which is drivably connected
to the final drive shaft 28. The speed responsive motor shutoff
mechanism of the present invention 1ncludes a member 58 disposed
on the drive shaft 52 for rotation therewith. The member 58
includes a plurality of generally radially extending grooves 60
formed therein, see Fig. 3 also. The grooves 60 are formed to
have inclined bottom surfaces 62 and the grooves each contain
a movable flyweight or spherical ball 64 which is movable along
the groove radially outwardly with respect to the drive shaft
. .,
52 in response to centrifugal force. The speed responsive motor
shutoff mechanism further includes an axially movable member 66
forming a valve closure member for interrupting the flow of
exhaust fluid from the chamber 38 to the chamber 40. The closure
member 66 is axially slidably supported by a hub portion 68 of
the motor end plate 44 and by the intermediate drive shaft 52.
The closure member 66 is operable to engage a seat 70 formed by
a transverse wall surface facing the interior chamber 38. The
closure member 66 is biased toward the seat 70 by a coil spring 72
disposed between a flange 74 on the closure member and the motor
end plate 44.
The closure member 66 includes a recess 76 opening to one
end thereof in which the member 58 is partially disposed. An
annular plate 78 is also disposed in the recess 76 and is engage-
able with the balls 64 even when they are disposed in their radially
innermost positions in the grooves 60. A circular disc spring
washer 80 is disposed between the plate 78 and the bottom of the
recess 76. The stiffness of the spring washer 80 is greater than
the stiffness of the spring 72 and the spring washer exerts a
biasing force in opposition to the spring 72. Accordingly, when

SC~3
the fluid pressure in the chambers 38 and 40 is essentially
the same the spring washer 80 holds the closure member 66 a
short distance away from the seat 70 as shown in Fig. 2.
Accordingly, when pressure fluid is introduced to the motor 14
on startuE somcexhaust fluid flow is allowed to pass through the
chambers 38 and 40 to enable the motor to start. Once the motor
14 has commenced to rotate the shaft 52 rapidly, the balls 64
are forced radially outwardly in the grooves 60 and due to the
inclined bottom surfaces 62 the balls force the plate 78 and the
closure member 6,6 to the right, viewing Fig. 2, to increase the
size of the passageway formed between the closure member and the
seat 70. Therefore, when the motor 14 is operating at greater
.,
than idle speed or greater than approximately ten percent of its
free speed, the exhaust flow is not impeded.
lS In normal operation of the tool 10 for running down and
tightening a threaded fastener, when the motor 14 is at rest and
the valve 20 is closed, the closure member 66 is in the position
shown in Fig. 2. When the valve 20 is moved to the position to
conduct pressure fluid through the passage 22 to the motor 14 the
initial flow of motive fluid permitted by the small opening between
the closure member 66 and the seat 70 is sufficient to allow the
motor to accelerate enough to cause the balls 64 to force the
closure member to the fully open position. The closure member 66
will remain in a substantially full open position with the spring
72 compressed until rotative speed of the motor 14 and the drive
shaft 52 decreases to approximately ten percent of the motor free
or unloaded speed. This reduced speed is normally commensurate
with the desired maximum torque to be delivered by the motor to
.~
the fastener being tightened. As the motor speed decreases to
the condition mentioned above, the bias of the spring 72 will
force the balls 64 radially inward in the grooves 60 overcoming
the reduced centrifugal forces acting on the balls and the closure
_5_

~ ~5tj~ ~
member will move toward the,seat 70. As the passageway formed
between the closure member 66 and the seat becomes more restricted
with movement of the closure member, the exhaust fluid pressure
in the chamber 38 increases in relation to the pressure in chamber
40 and a pressure force acting on the flange 74 will cause the
, .
closure member to move rapidly in^to engagement with the seat
overcoming the bias force of the spring washer 80. When the
exhaust flow is shut off entirely the motor 14 will stop and the
fluid pressure difference across the motor will quickly diminish
to reduce substantially the motor output torque whether or not
the valve 20 remains open or closed.
When the valve 20 is released by the tool operator the fluid
pressure in the motor 14 as well as the exhaust chamber 38 will
be reduced due to leakage flow and venting through the valve 20
in the closed position. When the fluid pressure in the chamber 38
decreases sufficiently, the spring washer 80 will move the closure
member 66 away from the seat 70 to the position shown in Fig. 2
and the shutoff mechanism will be ready for another operating
cycle of the tool 10.
What is claimed is:
. . .
. _
--6--
_ . _ _ .. . . . .. . . . _ . _

55~.f3
SUPPLEMENTARY DISCLOSURE
An alternate embodiment of the present invention is shown in Figures 4
and 5. Referring to Figure 4 the motor rotor output shaft portion 50 is
drivably connected to a coupling member 82 having cylindrical journal 83
5 and a plural;ty of spiral grooves 84 formed on the periphery thereof, as
shown also in Figure 5. The coupling member 82 is drivably connected to
the shaft 52. A closure member 86 similar to the closure member 66 is
mounted on the coupling member 82 and includes a hub portion 88 having
spaced apart holes 90 in which are disposed ball keys 92. The ball keys c
10 92 extend into the grooves 84 to form a driving connection between the
coupling member 82 and the closure member. The ball keys 92 are retained
in engagement with the closure member 86 and the coupling member 82 by a
spring band 94. Accordingly, the closure member 86 is operable to move
axially on the coupling member 82 between a shoulder 96 on the coupling
15 member and a retaining ring 98 also disposed on the coupling member. In
moving axially the closure member 86 also undergoes some rotation with
respect to the coupling member because of the coupling formed by the ball
keys 92 and the spiral grooves 84.
The shutoff mechanism sh~n in Figures 4 and 5 operates in a manner
20 similar to the mechanism shown in Figures 1 through 3, that is, when the
motor 14 is at rest and the valve 20 is closed the closuré member 86 nor-
mally assumes the position shown in Figure 4. However, because of the
limited motion coupling formed between the member 82, and the closure
member 86 the closure member may be in a further open position. Accord-
25 ingly, when the valve 20 ;s opened the motor 14 will accelerate the balls
64 to force the closure member 86 to the fully open position if in fact
it is not already in that position. The coupling formed between the closure
member 86 and the coupling member 82 will also assist in moving the closure
member toward the open position due to the inertia of the closure member.
When motor speed decreases due to increased torque and the balls 64
move radially inwardly in the grooves 60 the angular momentum of the ro-
.~

1~5SC~3
tating closure member 86 will urge it to move with respect to the coupling
member 82 rotatably and axially toward the valve seat 70. As the closure
member 86 approaches the seat 70 the reduced flow area formed between the
seat and the closure member will create a pressure differential acting
on the flange 99 of the closure member causing the same tg move rapidly
toward the closed position whereby the motor 14 will stop. As in the
embodiment of Figures 1 thru 3 the valve closure member 86 will remain
closed as long as the valve 20 is held open and a pressure differential
exists across the flange 99 of the closure member. When the pressure
in the chamber 38 is reduced upon closure of the valve 20 the spring
washer 80 will move the closure member 86 to the partially open position
shown in Figure 4 so that another operating cycle may be commenced upon
opening of the valve 20.
~1¢'~'' i
....' . ~

Representative Drawing

Sorry, the representative drawing for patent document number 1125593 was not found.

Administrative Status

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Event History

Description Date
Inactive: IPC from MCD 2006-03-11
Inactive: Expired (old Act Patent) latest possible expiry date 1999-06-15
Grant by Issuance 1982-06-15

Abandonment History

There is no abandonment history.

Owners on Record

Note: Records showing the ownership history in alphabetical order.

Current Owners on Record
COOPER INDUSTRIES, INC.
Past Owners on Record
WILLIAM, JR. WORKMAN
Past Owners that do not appear in the "Owners on Record" listing will appear in other documentation within the application.
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Document
Description 
Date
(yyyy-mm-dd) 
Number of pages   Size of Image (KB) 
Abstract 1994-02-16 1 16
Claims 1994-02-16 4 137
Drawings 1994-02-16 2 60
Descriptions 1994-02-16 8 289