U.S. patent number 3,616,864 [Application Number 04/880,663] was granted by the patent office on 1971-11-02 for torque-controlled motor shutoff for power tool.
This patent grant is currently assigned to Gardner-Denver Company. Invention is credited to Edwin J. Deremo, Clarence A. Sorensen.
United States Patent |
3,616,864 |
Sorensen , et al. |
November 2, 1971 |
TORQUE-CONTROLLED MOTOR SHUTOFF FOR POWER TOOL
Abstract
A torque-responsive shutoff mechanism for a torque-producing
power tool having a valve operable to shut off the flow of motive
pressure air to the tool motor. The shutoff valve includes an
elongated actuating rod which is releasably held by a plurality of
radially spaced balls which are operable to frictionally grip the
rod diameter. The gripping ball members are forced into engagement
with the rod by a driven member of a torque-sensing device
interposed in the drive train of the tool. The driving and driven
members of the torque-sensing device include interengaging sloped
surfaces which force the members to move axially relative to each
other upon reaching a predetermined resistance to rotation. The
radially spaced balls contained within a conical recess in the
driven member are relieved of their engaging force on the
valve-actuating rod upon axial movement of the driven member
whereby the shutoff valve is biased to the closed position. The
driving and driven members of the torque-sensing device are biased
into engagement by a variably compressible coil spring.
Inventors: |
Sorensen; Clarence A.
(Fruitport, MI), Deremo; Edwin J. (Spring Lake, MI) |
Assignee: |
Gardner-Denver Company (Quincy,
IL)
|
Family
ID: |
25376795 |
Appl.
No.: |
04/880,663 |
Filed: |
November 28, 1969 |
Current U.S.
Class: |
173/176; 192/150;
91/59 |
Current CPC
Class: |
F16D
43/20 (20130101); B25B 23/145 (20130101) |
Current International
Class: |
F16D
43/00 (20060101); B25B 23/14 (20060101); B25B
23/145 (20060101); F16D 43/20 (20060101); B23q
005/00 () |
Field of
Search: |
;173/12 ;91/59 ;192/150
;81/52.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leppink; James A.
Claims
What is claimed is:
1. In a torque tool:
a motor operable to rotatively drive a spindle;
a power supply;
shutoff means including an elongated actuating rod operable to
provide for said power supply to be connected to said motor and for
said power supply to said motor to be shut off, and the improvement
comprising:
torque-sensing rotation transmitting means interposed between said
motor and said spindle including driving and driven members having
complementary sloped surfaces providing for engagement therebetween
to transmit torque from said motor to said spindle, said driven
member being operable to move axially with respect to said driving
member upon sensing a predetermined torque produced by said motor,
and said driven member including a conical recess forming an
inclined surface substantially circumsurrounding and engaged with a
plurality of gripping members and forcing said gripping members
into engagement with said rod, said gripping members being
responsive to the axial movement of said driven member to release
said rod to provide for the shutoff of said power supply to said
motor, and adjustable biasing means operable to yieldably bias said
driving and driven members into engagement and to force said driven
member to forcibly engage said gripping members to hold said
gripping members in engagement with said rod.
2. The invention set forth in claim 1 wherein:
said gripping members comprise a plurality of balls radially spaced
with respect to said actuating rod.
3. In a torque tool:
a motor operable to rotatively drive a spindle;
a power supply;
shutoff means including an elongated actuating member movable to
provide for said power supply to be connected to said motor and for
said power to said motor to be shut off, and the improvement
comprising:
torque-sensing rotation transmitting means interposed between said
motor and said spindle including driving and driven members
operable to move axially relative to each other upon sensing a
predetermined torque produced by said motor, a plurality of members
spaced around and operable to be in frictional gripping engagement
with said actuating member for moving said actuating member,
surface means on one of said driving and driven members
circumsurrounding and engageable with said plurality of members to
hold said plurality of members in frictional gripping engagement
with said actuating member and in response to the relative axial
movement of said driving and driven members said plurality of
members are operable to release said frictional gripping engagement
with said actuating members to allow said actuating member to move
to shut off said power to said motor.
4. The invention set forth in claim 3 wherein:
said driving and driven members of said torque-sensing means
include complementary sloping surfaces operable to provide for
engagement between said driving and driven members to transmit
torque from said motor to said spindle, and said driven member
includes a substantially conical recess forming said surface means
engageable with said plurality of members and said driven member
operable to move axially with respect to said driving member in
response to a predetermined torque produced by said motor.
5. The invention set forth in claim 4 wherein:
said torque-sensing means includes adjustable biasing means
operable to yieldably bias said driving and driven members into
engagement.
Description
BACKGROUND OF THE INVENTION
In torque-producing power tools such as nutrunners, screwdrivers
and the like, various devices are known for sensing the torque
output of the tool and operating, upon sensing a predetermined
torque, to disengage the tool motor from the output spindle or to
shut off the power supply to the tool. A number of tool designs
include means operable to both shut off the tool motor and
disengage a clutch comprising part of the drive train of the
tool.
Prior art fluid-operated power tools which include releasable
clutch means operable to disengage the tool motor from the drive
spindle and simultaneously actuate a motive fluid shutoff valve are
disclosed in U.S. Pat No. 3,262,536 to R. C. Frisbie et al. and
U.S. Pat. No. 3,275,116 to P. W. Martin. Generally, known devices
are unduly complicated in design and comprise an excessive number
of mechanically interacting components which are subject to wear
and breakage thereby impairing the accuracy of torque control and
resulting in frequent malfunction. Many disengaging-type clutches,
which are widely used in prior art tools for controlling the torque
output thereof, are also subject to breakage due to repeated
impacting of the interengaging surfaces of the driving and driven
elements. Although releasable or disengaging-type clutches are
sometimes considered desirable in large portable torque tools, they
are unnecessary in the relatively smaller tools having low drive
train inertia and negligible operator reaction torque.
SUMMARY OF THE INVENTION
The present invention provides a torque control mechanism for a
power torque tool which is operable to sense a predetermined torque
transmitted to the drive spindle of the tool and actuate a shutoff
device to interrupt the power supply to the tool motor. In the
present invention there is provided a torque-sensing rotation
transmitting means interposed in the drive train of a pressure
fluid operated torque tool which is operable to sense a
predetermined torque and, accordingly, produce mechanical movement
sufficient to actuate a value to shut off pressure fluid to the
tool motor without requiring total disengagement of the tool motor
from the drive spindle.
The present invention also provides a torque-sensing device which
is operable to actuate a shutoff valve of a fluid operated tool
wherein mechanical movement is minimal and, accordingly, reliable
operation and accurate control of output torque may be obtained. In
the present invention a torque-sensing rotation transmitting device
comprising relatively movable driving and driven members is
operable to a cam a plurality of spherical members into
frictionally gripping engagement with a shutoff valve actuator to
hold the valve in the open position. In response to a predetermined
torque transmitted from the driving to the driven member small
axial movement therebetween operates to relieve the camming force
on the spherical members whereby the gripping engagement of the
actuator is relieved to allow the valve to close. The present
invention may be advantageously utilized in various types of power
torque tools including what are known as push-to-start tools and
manual throttle valve controlled types.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a longitudinal section view of a pressure fluid operated
torque tool according to the present invention;
FIG. 1a is a continuation of FIG. 1 from the line a--a;
FIG. 2 is a section view taken substantially along the line 2--2 of
FIG. 1;
FIG. 3 is a perspective detail view of the driving and driven
members of the torque-sensing device.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 and 1a a power torque tool is illustrated in
the from of a portable screwdriver, generally designated by the
numeral 10. The tool 10 includes a housing 12 threadably engaged
with a head portion 13 and containing a pressure fluid operated
rotary vane motor 14 of a type well known in the art of industrial
power tools. The motor 14 includes a rotor 16 suitable journaled in
bearings 18 and 20. The rotor 16 includes an integral shaft portion
22 which is drivably engaged with a planetary gear speed reduction
unit 24 having an output shaft formed by the planet gear carrier
26. The tool 10 is adapted to be connected to a power supply such
as a source of pressure fluid, not shown, by means of a connector
28 mounted on the head portion 13. The connector 28 is in fluid
flow communication with a passage 30 centrally positioned in the
head. Located in the passage 30 is a pressure fluid shutoff valve
assembly 32 including a valve guide 34, valve closure member 36,
and a valve seat 38.
In the position shown in FIG. 1a the closure member 36 is in the
seated or closed position preventing the flow of pressure fluid to
the motor inlet port 40 from passage 30 by way of the passages 42
and 44 in the valve guide 34 and the passage 46 in the housing 13.
Pressure fluid when supplied to the motor 14, is exhausted
therefrom by suitable passage means, not shown.
The tool 10 includes a hollow detachable cover member 48 threadedly
engaged with the housing 12. The cover 48 includes a nose portion
50 having a bore for receiving a cylindrical bushing 52. The
bushing 52 rotatably journals a spindle 54 which in turn is
drivably engaged with a screwdriver bit 56. The bit 56 is retained
in engagement with the spindle 54 by a spring-biased screwfinder 58
and sleeve 60 threadably retained on the housing nose portion 50.
The spindle 54 extends into the interior of the cover 48 and
includes a slot 62 providing clearance for a transverse pin 64
suitably retained in a rotating thrust collar 66 which bears
against a thrust washer 68. The spindle 54 is drivably engaged with
a torque-sensing rotation transmitting means generally designated
by the numeral 70. The torque-sensing means 70 includes a driving
member 72 having a shaft portion 74 nonrotatably engaged with
respect to the planet carrier 26 by suitable means such as
complementary splines. The driving member 72 is provided with a
pair of transverse sloping surfaces 76, one shown, see FIG. 3,
engageable with coacting surfaces 78 on a driven member 80. The
driven member 80 is provided with an integral sleeve portion 82
coaxially surrounding the spindle 54 and nonrotatably engaged
therewith by means of ball keys 84 located in the keyway 86 and key
slot 88 on the spindle 54 and sleeve portion 82, respectively. The
ball keys 84 are radially retained by a tubular sleeve 90 which in
turn is retained on the driven member 80 by a ring 92. The tubular
sleeve 90 also retains a ball key 94 positioned partially in a
groove 96 in the hub 98 of the driving member 72 and partially in a
radial aperture 100 in the driven member 80. The groove 96 is
dimensioned to permit limited axial movement between the driving
member 72 and driven member 80 and cooperates with the ball key 94
to prevent total disengagement of the two members. The driving and
driven members are axially biased into engagement by a coil spring
102. The axial biasing force produced by the spring 102 may be
varied by adjustment of a tubular nut 104 threadably engaged with
the driving member 72.
Referring to FIGS. 1 and 2, the driven member 80 includes a conical
recess 106 opening to one end and forming an inclined surface
circumsurrounding and forcibly engaging a plurality of radially
spaced spherical members or balls 108. The balls 108 are located in
radial holes 110 in the hub 98 of the driving member. The balls 108
are engaged by the surface 106 to be forced radially inwardly into
fractional gripping relationship with an actuating member for the
shutoff valve 32 comprising an elongated cylindrical cross section
rod 112. The rod 112 extends longitudinally through the spindle 54,
driving member 72 and rotor 16 to engage the valve closure member
36 for actuating the same to open in response to axial movement of
the spindle 54 and torque-sensing means 70 toward the motor 14. In
response to release of the actuating rod by the gripping balls 108,
an unbalanced pressure force caused by pressure fluid acting on the
surface 114 of the valve closure member 36 will operate to close
the valve shutting off the motive fluid supply to the motor 14.
The torque-sensing means 70 is axially movably held in the shutoff
valve closed position shown in FIG. 1 by a bias spring 116 located
between the driving member 72 and the planer carrier 26 and by a
spring 118 engaging the tubular nut 104 and the thrust collar
66.
To operate the tool 10, upon engagement of a fastener to be driven
by the bit 56, application of an axial force by the tool operator
against the bias of the spring 116 will move the bit 56, spindle
54, and torque-sensing means 70 axially toward the motor 14. The
balls 108, forced into gripping relationship with the rod 112 by
the driven member 80, will actuate the rod to open the valve
closure member 36 thereby supplying motive pressure fluid to the
motor 14. With pressure fluid supplied to the motor 14 the same
will rotatively drive the spindle 54 through the gear reduction
unit 24 and the torque-sensing means 70. The rod 112 nonrotatably
gripped by the balls 108 will rotate with the torque-sensing means
70 and is suitably journaled by the bore 130 of the rotor 16 to
permit relative rotation with respect thereto. The torque applied
to the spindle by the motor 14 is sensed by the driving and driven
members 72 and 80, respectively, and the force transmitted between
the complementary sloped surfaces 76 and 78 produces a component
tending to move the driven member 80 axially relative to the
driving member 72. When said force component exceeds the biasing
force produced by the spring 102 the driven member will move to
release the engagement of the balls 108 with the inclined surface
106 whereby the gripping force of the balls against the rod 112
will be relieved and the valve closure member 36 will move to close
in response to pressure fluid force on the surface 114, shutting
off motive pressure fluid to the tool motor 14. Axial movement of
the rod 112 on closing of the valve is limited by the transverse
pin 64.
When the tool motor 14 shuts off indicating that maximum torque, as
predetermined by the adjustable biasing force of the spring 102,
has been applied to the fastener the operator will remove the tool
from the work. The spring 116 will reposition the spindle 54 and
torque-sensing means 70 to the position shown in FIG. 1. Since the
relative movement of the balls 108 with respect to the rod 112
tends to move the balls away from the inclined surface 106, the
gripping force between the balls and rod will be relieved
sufficiently to allow the torque-sensing means 70 to be
repositioned by the spring 116 for the next operating cycle.
As may be appreciated from the foregoing, the torque-sensing means
70 operates to control the torque output of the tool 10 with a
minimum of mechanical movement but yet with accuracy and great
reliability. Since the driving and driven members 72 and 80 do not
disengage completely there is minimal wear and chance of failure
from breakage commonly encountered with prior art torque control
clutches and similar devices.
The present invention need not be limited to the tool embodiment
illustrated. For example, some types of pressure fluid operated
torque tools utilize a manually controlled throttle valve for
starting the operating cycle of the tool. The throttle valve is
interposed between the shutoff valve, such as the valve 32, and the
pressure fluid supply. In such an arrangement the shutoff valve
would be spring biased to be in the open position and in response
to release of the actuating rod by the torque-sensing means the
shutoff valve would be closed by a pressure fluid force acting on a
surface such as the surface 114 in opposition to the spring bias.
The aforementioned manually controlled valve when released by the
operator would be operable to vent pressure fluid from the passage
upstream of the shutoff valve relieving the pressure fluid force on
the shutoff valve and allowing the aforementioned bias spring to
reopen the shutoff valve for the next operating cycle. Moreover,
the present invention may be used with tools having other sources
of motive power, namely, electric motor-driven tools whereby the
actuating rod 112 may, for example, operably engage a spring-biased
switch to shut off motive energy to the tool motor.
* * * * *