U.S. patent number RE28,899 [Application Number 05/564,272] was granted by the patent office on 1976-07-13 for torque control apparatus.
This patent grant is currently assigned to S. Himmelstein and Company. Invention is credited to Sydney Himmelstein, Richard S. Tveter.
United States Patent |
RE28,899 |
Himmelstein , et
al. |
July 13, 1976 |
Torque control apparatus
Abstract
A torque-applying apparatus having one or more torque motors
each arranged for forcibly threading a first threaded member into
tightened association with a corresponding second threaded member.
A control is provided for controlling the operation of each torque
motor to firstly seat the first threaded member relative to the
second threaded member by a rapid threading operation at a low
torque. When the seated condition of all of the threaded members is
sensed, the control automatically operates each torque motor to
slowly apply gradually increasing higher torque to provide a
preselected maximum-torque, tightened condition of the threaded
members.
Inventors: |
Himmelstein; Sydney (Lake
Forest, IL), Tveter; Richard S. (Barrington, IL) |
Assignee: |
S. Himmelstein and Company (Elk
Grove Village, IL)
|
Family
ID: |
26981714 |
Appl.
No.: |
05/564,272 |
Filed: |
April 2, 1975 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
288379 |
Sep 12, 1972 |
|
|
|
Reissue of: |
318864 |
Dec 27, 1972 |
03827506 |
Aug 6, 1974 |
|
|
Current U.S.
Class: |
173/182; 91/59;
91/29 |
Current CPC
Class: |
B25B
23/1456 (20130101) |
Current International
Class: |
B25B
23/14 (20060101); B25B 23/145 (20060101); B25B
023/14 () |
Field of
Search: |
;173/12,20 ;81/52.5
;91/29,59 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Attorney, Agent or Firm: Wegner, Stellman, McCord, Wiles
& Wood
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application comprises a continuation-in-part of application
Ser. No. 288,379, filed Sept. 12, 1972, for a "Torque Control
Apparatus", said application being now abandoned.
Claims
We claim:
1. In a torque-applying apparatus having torque means for forcibly
threading a first threaded member into tightened association with a
second threaded member, control means for controlling the operation
of said torque means comprising:
seating means for causing said torque means to develop a force in
threading the first member into a seated association with said
second threaded member;
means for sensing the amount of torque applied between said
threaded members; and
setting means responsive to said sensing means for causing said
torque means to develop a gradually increasing higher .[.force.].
.Iadd.torque .Iaddend.for applying a preselected maximum torque
between said seated threaded members to provide a preselected
tightened condition of said threaded members.
2. The torque-applying control apparatus of claim 1 wherein said
means for causing said torque means to develop a higher .[.force.].
.Iadd.torque .Iaddend.includes means for slowly increasing the
applied torque whereby the applied torque may be accurately limited
to said preselected maximum torque when sensed by said sensing
means.
3. The torque-applying control apparatus of claim 1 wherein said
torque means comprises fluid pressure means and said means for
causing said torque means to develop a higher .[.force.].
.Iadd.torque .Iaddend.includes restrictor means for slowly
increasing the applied torque whereby the applied torque may be
accurately limited to said preselected maximum torque when sensed
by said sensing means.
4. The torque-applying control apparatus of claim 1 wherein said
seating means comprises means for causing said first member to be
threaded at high speed at low torque and said setting means
comprises means for causing said torque .[.force.]. to be slowly
increased to said preselected maximum.
5. The torque-applying control apparatus of claim 1 further
including means for discontinuing application of torque between
said threaded members substantially immediately upon reaching said
maximum torque.
6. The torque-applying control apparatus of claim 1 further
including means for indicating the amount of torque applied between
said threaded members.
7. The torque-applying control apparatus of claim 1 wherein said
torque means comprises rotary pneumatic motor means.
8. The torque-applying control apparatus of claim 1 wherein said
torque means comprises rotary pneumatic motor means for rotating
said first threaded members and said sensing means comprises a
torquemeter interconnected between said motor means and said second
threaded member.
9. The torque-applying control apparatus of claim 1 including
indicating means for providing a signal whenever the torque applied
between the threaded members is less than a preselected low
torque.
10. The torque-applying control apparatus of claim 1 including
indicating means for providing a signal whenever the torque applied
between the threaded member is greater than a preselected high
torque.
11. The torque-applying control apparatus of claim 1 including
indicating means for providing a signal whenever the torque applied
between the threaded members reaches the preselected maximum
torque.
12. In a torque-applying apparatus having torque means for forcibly
threading a first threaded member into tightened association with a
second threaded member, control means for controlling the operation
of said torque means comprising:
means for sensing the amount of torque applied between said
threaded members;
setting means responsive to said sensing means for causing said
torque means to develop a gradually increasing .[.force.].
.Iadd.torque .Iaddend.for applying a preselected maximum torque
between said seated threaded members to provide a preselected
tightened condition of said threaded members; and
means for causing said torque means to apply a pulse of high torque
momentarily between said threaded members at the initiation of
application of the low seating torque therebetween by said seating
means to positively initiate the threading operation.
13. The torque-applying control apparatus of claim 12 wherein said
pulse applying means comprises means for utilizing energy stored in
the torque means at the conclusion of a prior torque-applying
threading operation.
14. The torque-applying control apparatus of claim 12 wherein said
pulse applying means comprises means for momentarily operating said
setting means for developing said high torque.
15. The torque-applying control apparatus of claim 12 wherein said
torque means comprises means operated by fluid pressure and said
pulse applying means comprises means for momentarily applying high
fluid pressure to said torque means.
16. In a torque-applying apparatus having torque means for forcibly
threading a plurality of first threaded members into tightened
association with a corresponding plurality of second threaded
members, control means for controlling the operation of said torque
means comprising:
seating means for causing said torque means to develop a
.[.force.]. .Iadd.torque .Iaddend.in threading the first members
into seated association with said second members;
means for sensing the amount of torque applied between said
threaded members;
setting means responsive to said .[.sening.]. .Iadd.sensing
.Iaddend.means for causing said torque means to develop a gradually
increasing higher .[.force.]. .Iadd.torque .Iaddend.for applying a
preselected maximum torque between said seated threaded members to
provide a preselected tightened condition of each of said threaded
members; and
means for preventing operation of said setting means until each of
said first threaded members is in seated association with its
associated second threaded member.
17. The torque-applying control apparatus of claim 16 wherein said
torque means comprises means operated by fluid pressure and means
for applying substantially the same pressure to torque each pair of
associated first and second threaded members.
18. The torque-applying control apparatus of claim 16 werein said
torque means comprises means operated by fluid pressure and said
.[.seating.]. .Iadd.setting .Iaddend.means includes a flow
restrictor .[.in the fluid pressure means.]. for controlling the
buildup of torque .[.pressure.]. applied between said threaded
members.
19. The torque-applying control apparatus of claim 16 wherein said
torque means comprises a plurality of fluid operated means and
.Iadd.said apparatus includes .Iaddend.a plurality of
pressurized-fluid supply controls associated one each with said
fluid operated means.
20. The torque-applying control apparatus of claim 19 wherein a
common fluid pressure source is provided with each of said supply
controls being connected thereto.
21. The torque-applying control apparatus of claim 19 wherein each
of said supply controls includes adjustable means for slowly
increasing .Iadd.the fluid pressure provided to the fluid operated
means for correspondingly gradually increasing .Iaddend.the applied
torque.
22. In an apparatus for applying torque to a first threaded member
to sequentially firstly seat and then set said member relative to a
second threaded member with a preselected maximum torque, a fluid
operated torque motor means, means for sensing torque applied
between said first and second members, means for causing torque to
be delivered from said torque motor means to seat said first member
relative to said second member by a relatively low torque, high
speed threading of the first member to the seated condition, second
means responsive to the sensing means sensing the seated condition
for causing the torque delivered from said torque motor means to
slowly increase to set said seated threaded member, and means
responsive to the sensing of the preselected maximum torque by said
sensing means to terminate torque delivery from the torque motor
means with the first member set accurately at said preselected
torque.
23. The torque applying apparatus of claim 22 wherein said first
means comprises solenoid operated apparatus associated with said
torque motor means for causing the torque delivery therefrom to be
said low torque delivery.
24. The torque applying apparatus of claim 22 wherein said second
means comprises solenoid operated apparatus associated with said
torque motor means for causing the torque delivery therefrom to be
said slowly increasing torque delivery.
25. In an apparatus for applying torque to a first threaded member
to sequentially firstly seat and then set said member relative to a
second threaded member with a preselected maximum torque, torque
means, means for causing said torque means to thread the first
member to a seated condition on the second member, sensing means
sensing said seated condition, and mechanism associated with said
torque means for causing said torque means to provide a low kinetic
energy gradually increased torque delivery between said first and
second members to tighten said seated members to a
preselected-torque seated condition, and means for terminating the
torque delivery substantially immediately upon reaching said seated
condition.
26. Torque applying apparatus of claim 25 wherein said mechanism
includes electrically actuated control means and said sensing means
provides an electrical signal suitable to actuate said mechanism
control means. .Iadd. 27. The torque-applying control apparatus of
Claim 1 wherein said torque means includes a torque motor and said
setting means includes means for slowly building up the input to
the torque motor to provide the gradually increasing torque between
said seated threaded members. .Iaddend..Iadd. 28. The
torque-applying control apparatus of Claim 12 wherein said torque
means includes a torque motor and said setting means includes means
for slowly building up the input to the torque motor to provide the
gradually increasing torque between said seated threaded members.
.Iaddend..Iadd. 29. The torque-applying control apparatus of Claim
16 wherein said torque means includes a torque motor and said
setting means includes means for slowly building up the input to
the torque motor to provide the gradually increasing torque between
said seated threaded members. .Iaddend..Iadd. 30. The
torque-applying control apparatus of Claim 25 wherein said torque
means includes a torque motor and said setting means includes means
for slowly building up the input to the torque motor to provide the
gradually increasing torque between said seated threaded members.
.Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to torque-applying apparatus and in
particular to controls for automatically controlling such
apparatus.
2. Description of the Prior Art
In one form of torque-applying system, nut members are run onto
male threaded studs or the like, to provide a tightened, set,
condition therebetween. In certain applications, a number of such
nut setting tools are operated concurrently to effect a setting of
a plurality of nuts for improved speed and efficiency in
manufacture of machinery and the like. To prevent overtightening of
the nuts, control devices have been incorporated to anticipate the
fully tightened condition and thereby discontinue application of
torque in anticipate of the final condition which is reached by the
inertia of the system. Such anticipatory circuits have the
disadvantage of relative inaccuracy in the elements of the
torque-applying system which may include solenoid valves having
variable time delay characteristics and the like. One example of a
prior art torque control system is shown in U.S. Pat. No. 3,596,718
of Charles Dennis Fish et al.
SUMMARY OF THE INVENTION
The present invention comprehends an improved control means for use
in a torque applying apparatus providing improved accurracy in
setting of a first threaded member in tightened association with a
second threaded member. The invention comprehends such a control
means causing the torque means of the apparatus to develop a
relatively low torque for rapidly threading the first threaded
member into a seated association with the second threaded member,
and subsequently causing the torque means to slowly develop a
higher torque for applying a preselected maximum torque between the
seated threaded members to provide a desired preselected tightened,
or set, condition of the threaded members. The control includes
means for sensing the amount of torque applied between the threaded
members, and the setting means is responsive to the sensing means
to effect the desired torque setting of the threaded members.
Means may be provided in the control for apply a starting pulse
momentarily between the threaded members at the initiation of
application of the low seating torque to break the members free at
the start of the threading cycle. The pulse applying means may
comprise means for applying high torque as used in the setting
operation momentarily to the threaded members prior to initiation
of the seating operation.
The invention comprehends providing a plurality of such torque
means for concurrently setting a plurality of first threaded
members into tightened association with a corresponding plurality
of second threaded members. The control may be provided with means
for preventing operation of said setting means until each of the
first threaded members is in seated association with its associated
second threaded member.
The torque means may comprise a pneumatic motor, and where a
plurality of such motors is utilized for setting concurrently a
plurality of threaded members, similar pneumatic pressure may be
applied concurrently to each of the motors.
Thus, the torque-applying apparatus control of the present
invention provides a rapid setting of threaded members without
overshooting of the torque as may result from the rotation inertia
of the system as in conventional setting devices. The control
provides a slow buildup of the setting torque to define a time
expansion means, avoiding inaccuracies in the setting of the
threaded members such as may result from variable valve operation
time constants, threaded member characteristics, and rate of
setting. The control is adapted to be utilized with existing
torque-applying apparatuses and includes simplified control means
including automatic signalling displays for facilitated setting of
a plurality of such threaded means. The setting torque is not
determined by anticipatory control means, but rather, is determined
accurately by the preselected value as reached in the set condition
of the threaded members. The control provides a continuous
monitoring of the applied torque through improved strain gauge
torquemeter means and associated torque readout and control/logic
circuitry. Permanent records of the torque values applied to the
different threaded means may be provided through suitable
associated recording means.
The torquemeter may comprise a hollow torquemeter having one
portion connected to the torque motor and another portion to the
second of the threaded members so as to provide a constant
indication of the torque applied by the torque motor between the
threaded members. Other torquemeter types, such as an in-line
crystal or stain gauge transducers, may be used.
The torquemeter disclosed herein comprises an improved torquemeter
eliminating spurious signals from extraneous bending and thrust
loads and is substantially independent of temperature
variations.
The torque-applying apparatus control of the present invention is
extremely simple and economical of construction while yet providing
the highly desirable features discussed above.
BRIEF DESCRIPTION OF THE DRAWING
Other features and advantages of the invention will be apparent
from the following description taken in connection with the
accompanying drawing wherein:
FIG. 1 is a schematic block diagram of a torque-applying apparatus
having a control embodying the invention;
FIG. 2 is a diametric section of the torque-applying apparatus;
FIG. 3 is a schematic wiring diagram of the control; and
FIG. 4 is a graph illustrating the torque conditions during the
seating and setting operations of the torque-applying
apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the exemplary embodiment of the invention as shown in the
drawing, a torque-applying apparatus generally designated 10
comprises means for threading a first threaded member 11 onto a
second threaded member 12. In the illustrated embodiment, first
threaded member 11 comprises a nut and second threaded member 12
comprises a stud onto which the nut is threaded. Torque to effect
the threading operation is provided by a torque motor 13 having a
spindle 14 adapted to rotate the nut 11. The spindle extends
through a hollow reaction torquemeter 15 which is connected between
the torque motor 13 and the support 16 carrying the stud 12 to
provide constantly a signal indicating the amount of torque
developed by the torque motor in threading the nut onto the stud.
In the illustrated embodiment, a plurality of nuts are threaded
concurrently to a corresponding plurality of studs, and more
specifically in FIG. 1, a second station is illustrated wherein a
second torque motor 13a is shown in association with a second
torquemeter 15a for controlling the setting of a second nut 11a on
a second stud 12a. As will be obvious to those skilled in the art,
any suitable number of such stations may be paralleled therewith.
However, in describing the structure of the invention, the
description will be limited primarily to the first described
structure utilizing torque motor 13, spindle 14, and torquemeter
15, it being understood that the other stations are substantially
identical thereto.
As shown in FIG. 2, torquemeter 15 includes a torque transmitting
tube 17 and a torque measuring tube 18 carrying suitable strain
gauges 19 defining a transducer for providing an electrical signal
corresponding to the torque being transmitted through the
torquemeter. The torque motor 13 includes an end flange 20 having
the torque transmitting tube 17 secured thereto by means of bolts
21 extending through motor flange 20 and a turned flange 22 at one
end of the torque transmitting tube. The other end of the torque
transmitting tube is provided with a flange 23 which is secured to
the support 16 by means of bolts 24 threaded into an intermediate
support 25 which is, in turn, secured to the flange 23 by bolts 26.
The spindle 14 extends coaxially through the torque measuring tube
18 and includes a socket head 27 adapted to engage the nut 11 for
threading it onto the stud 12 as an incident of rotation of the
spindle 14 by the torque motor 13.
The torquemeter 15 comprises an improved hollow reaction
torquemeter which is described more fully in copending application
Ser. No. 238,239 of Richard S. Tveter, identified as "Hollow
Reaction Torquemeter," and owned by the assignee hereof, to which
application reference may be had for more specific details of the
construction of the torquemeter. The present invention is directed
more specifically to the means for controlling the torque motors by
the torquemeters to provide a facilitated accurate setting of the
nuts as discussed below.
In the illustrated invention, the torque motors comprise
pneumatically operated air motors, it being understood that other
suitable torque motors, such as hydraulic or electric torque
motors, may be utilized by suitable modifications of the control as
will be obvious to those skilled in the art. Thus, in the
illustrated embodiment, air is supplied to the pneumatic control
system generally designated 28 from a source 29 of pressurized air
which, illustratively, may have a pressure of approximately 100
p.s.i. The air is delivered to a high pressure supply portion 30
and to a low pressure supply portion 31 of the pneumatic control 28
through a suitable distribution duct 32. The high pressure control
includes a conventional high pressure regulator 33 and a two-way
solenoid valve 34 which comprises a normally closed valve. A
restrictor illustratively in the form of a needle valve 35 is
connected in series with the regulator 33 and valve 34 for
providing a slow buildup of high pressure when a second solenoid
valve 36 comprising a normally closed three-way valve leading to
air motor 13 is opened. The low pressure control includes a
conventional low pressure regulator 37 for regulating the pressure
illustratively at a low pressure of approximately 50 p.s.i.
connected in series with a conventional check valve 37 which is
connected to the solenoid valve 36 through a common connecting duct
39. As indicated above, additional nut setting devices may be
provided in parallel and, thus, additional torque motor solenoid
valves, such as solenoid valve 36a, may be provide in parallel with
solenoid valve 36 for concurrently operating each of the plurality
of nut setting devices. The operation of the solenoid valves 34 and
36 (including solenoid valve 36a, etc.) is controlled by a suitable
electrical control 40 through suitable electrical conductors 41
(41a etc.), 42 (42a etc.) as a function of the signals delivered
from the torquemeters 15 (15a etc.) connected to control 40 by
suitable conductors 43 (43a etc.). Suitable operating power may be
provided to control 40 by power supply lead 44 and operation of the
system may be manually controlled by a conventional normally closed
"start" pushbutton station 45 connected to the control 40 by
suitable conductors 46.
Each additional nut setting device is preferably connected to a
separate air supply control system 28a etc. as shown in FIG. 1.
Such individual air supplies to the different air motors permit
adjustment of the air delivery to the air motors for accurate
correlation with the desired torque profiles which are a function
of the characteristics of the individual air motors. Thus, optimum
control of a plurality of concurrent threading operations is
obtained.
Control 40 is arranged to provide a two-step tightening of the nut
14 on stud 12 to permit high accuracy in the setting of the nut on
the stud with a preselected maximum torque. As shown in FIG. 4,
control 40 operates the air motor 13 to provide a relatively low
rundown, or seating, torque which quickly threads the nut onto the
stud into a seated condition, as shown at 47 on the torque time
graph. When the nut reaches the seated condition, the torque rises
rapidly as shown at 48 to a peak 49 which is above a preselected
seating torque T.sub.c 50 and below a low torque limit T.sub.L 51.
At this point, control 40 opens solenoid valve 34 which, by virtue
of the flow restriction afforded by needle valve 35, provides a
slow buildup of torque, as shown at 52, to a maximum preselected
torque 53 which is approximately at a preselected set torque 54. As
shown in the graph of FIG. 4, the control sets maximum torque 55 as
an upper safety limit in operation of the system above the
preselected maximum desired torque 53, as will be brought out more
fully hereinafter. When the preselected torque 53 is reached, the
torque quickly drops to zero, as shown at 56.
As shown at 57 in FIG. 4, a pulse of high pressure is provided at
the initiation of the threading cycle to break the nut free on the
stud and assure threading thereof to the seated condition. Once the
nut is broken free, the torque applied is the relatively low torque
47 as discussed previously.
Control 40 is more specifically illustrated in FIG. 3. The signal
from the torquemeter strain gauge 19 is delivered to an amplifier
(d-c or carrier type) suitable for use with conventional strain
gauges. Illustratively, the amplifier may comprise a Model 8000
amplifier manufactured by S. Himmelstein & Co., the assignee
hereof, a Model 311A amplifier manufactured by the Hewlett-Packard
Co., a Model 3C66 amplifier manufactured by Tektronix, Inc., and
the like. The output from amplifier 58 preferably comprises a
standardized voltage directly proportional to the measured torque
developed by the torque motor 13. The output voltage from the
amplifier is concurrently applied to the input of four voltage
comparators 59, 60, 61 and 62. Voltage comparator 59 has a second
reference input voltage delivered thereto from a stable power
supply 63 corresponding to the torque T.sub.c illustrated in FIG.
4. Voltage comparator 60 has a second reference input voltage
delivered thereto from a stable power supply 64 corresponding to
the torque T.sub.L of FIG. 4. Comparator 61 has a second reference
input voltage delivered thereto from a stable power supply 65
corresponding to torque T.sub.S of FIG. 4. Voltage comparator 62
has a second reference input voltage delivered thereto from a
stable power supply 66 corresponding to torque T.sub.H of FIG. 4.
The voltage comparators function in the conventional manner so that
when the voltage delivered from amplifier 58 is at least equal to
the reference voltage delivered from the power supplies 63, 64, 65
and 66 to a comparator, that comparator changes state in that it
goes from zero to saturation. As is well known to those skilled in
the art, other voltage comparators may be employed such as those
that will go from plus to minus saturation, a solid state switch or
diode coupled relay being utilized in combination therewith.
The output change from the voltage comparators is delivered to
corresponding sensitive relays 67, 68, 69 and 70. As will be
obvious to those skilled in the art, the sensitive relays may
comprises electronic switches, and may have four normally open
contacts 67a, 68a, 69a and 70a. Voltage comparators are
conventional devices manufactured by a large number of
manufacturers, such as Texas Instruments, Inc., Fairchild Camera
and Instrument Corporation, etc. The voltage comparators combine
with the sensitive relays to form a bistable trip with an
adjustable trip point, a voltage sensitive relay driver, or
adjustable solid state meter relay. As is well known in the art,
combination assemblies of such voltage comparators and sensitive
relays are manufactured by manufacturers such as California
Electronic Manufacturing Co., Alamo, Calif.
As shown in FIG. 3, each of the normally open contacts 67a-70a is
connected in series with an electromechanical relays 71, 72, 73 and
74, respectively. A fifth relay 75 is provided with a coil 75a is
used for resetting the control, as will be brought out more fully
hereinafter.
Power is supplied to the control through power supply leads 76 and
77 from a suitable direct current power supply (not shown). Reset
coil 75a is connected in series with the normally closed pushbutton
45 contacts across the power supply to energize the relay and
thereby close normally open contacts 75b, 75c, 75d and 75e
connected at one side to power supply lead 76. Assuming that the
torque motor 13 has not as yet developed any torque, each of the
other relays 71, 72 and 73 is energized. Pushbutton 45 includes a
normally open set of contacts 45a which are closed by the momentary
operation of the pushbutton station at the initiation of a new
threading operation, concurrently with the operation of the
normally closed contacts. Illustratively, the pushbutton unit may
comprise a single unit having the two different sets of contacts.
Energization of the high pressure solenoid 34a of solenoid valve 34
opens the valve to apply a pulse of high pressure to air motor 13
breaking free the nut 11 on stud 12 to provide a positive start of
the threading operation. Release of the pushbutton opens the
contacts 45a to de-energize solenoid 34a. The solenoid 36a of
solenoid valve 36 is energized at this time from the power supply
lead 76 through the normally closed contacts 72c. Thus, low
pressure air is delivered to the air motor 13 at this time from the
supply 29 through regulator 37, check valve 38, duct 39 and open
solenoid valve 36.
The torque developed by the air motor, when operated with the low
pressure, remains relatively low, as shown at 47 in the graph of
FIG. 4, until the nut seats itself relative to the stud 12 at which
time the torque developed by the air motor 13 rises to peak 49.
When the torque reaches the setting torque 50, relay coil 74a is
energized by the closing of contact 70a under the control of
sensitive relay 70. Relay coil 74a latches itself in by means of
the normally open latching contacts 74b of the relay 74 which are
connected in series with the now closed normally open contacts 75b.
A second set of normally open contacts 74c are closed by the
energization of relay coil 74a to reconnect high pressure solenoid
valve solenoid 34a to power supply lead 75, thereby applying high
pressure to the air motor 13 through the series connection from the
air supply 29 of high pressure regulator 33, solenoid valve 34,
needle valve 35, duct 39 and open solenoid valve 36.
The pressure slowly increases as controlled by the restrictor
action of needle valve 35 so as to provide a gradually increasing
torque, as shown at 52 in FIG. 4. Until the torque reaches the low
torque limit 51, a "Low" lamp 78 connected to power supply lead 77
is energized through a set of normally closed contacts 73c of relay
73. When the torque reaches the low limit torque 51 as illustrated
in FIG. 4, the relay coil 73a is energized by the closing of
contact 69a by sensitive relay 69, thereby opening the contact 73c
to deenergize lamp 78 and close normally open contacts 73b
connected in series with now closed contact 75c of the relay 75 to
provide a holding circuit paralleling contact 69a.
When the torque reaches the preselected desired torque 54 as shown
in FIG. 4, relay coil 72a is energized by the closing of contact
68a under the control of sensitive relay 68. The relay coil is then
latched in through the closing of normally open contacts 72b
connected in series with the now closed contacts 75d and solenoid
valve 36 is closed by the deenergization of solenoid 36a resulting
from the opening of normally closed contacts 72c. Should the torque
rise beyond the preselected point 53 to a high limit torque 55, as
shown in FIG. 4, relay coil 71a is energized by the closing of
contact 67a by sensitive relay 67. The coil is latched in by the
closing of normally open contacts 71b connected in series with the
now closed contacts 75e and a set of normally open contacts 71c is
closed to energize a "High" lamp 79 to indicate the high torque
condition. Thus, lamps 78 and 79 cooperatively provide an
indication that the torque applied by the air motor 13 to the
threaded members is either below the low torque limit 51 or above
the high torque limit 55.
Diode suppressors may be connected in parallel with the different
coils for limiting the magnitude of transient spikes in the
operation of these inductive elements. Thus, diodes 80a is
connected in parallel with relay coil 71a, diode 80b is connected
in parallel with relay coil 72a, diode 80c is connected in parallel
with relay coil 73a, diode 80d is connected in parallel with relay
coil 74a, and diode 80e is connected in parallel with relay coil
75a. Diode 80f is connected in parallel with valve solenoid 36a and
diode 80g is connected in parallel with valve solenoid 34a.
The operation of normally closed Reset pushbutton 45 resets the
entire control by de-energizing the relay coil 75a so as to open
contacts 75b, 75c, 75d, and 75e, thus opening the holding circuits
to each of the relay coils 71a, 72a, 73a and 74a.
As will be obvious to those skilled in the art, the use of solid
state logic and driver circuits may be substituted for the
electromechanical relay means disclosed. Alternating current relay
coils and solenoid valves similarly may be utilized so that the
alternating current power supply may be employed instead of the
direct current power supply disclosed. Further, the torques 50 and
51, as shown in the graph of FIG. 4, may be made to coincide,
and/or similarly, the torques 51 and 54 may be made to coincide to
provide a modified operation of the control.
As indicated above, the control contemplates the concurrent
threading of a plurality of nuts on a corresponding plurality of
studs such as in mass production techniques. The control functions
to assure that all nuts are seated before initiating the high
pressure setting operation wherein high torque 52 is applied to
slowly reach the desired preselected maximum torque 53 in each of
the associated nut and stud sets. To provide this functioning, a
set of normally open contacts 81 is provided in series with switch
74c and high pressure valve solenoid 34a and a set of normally open
contacts 82 is connected in series with the holding contacts 74b
and 75b associated with relay coil 74a. The contacts 81 and 82 are
closed by the energization of the relay coil 74a of the high
pressure control relay 74 of a second control 40a substantially
similar to control 40 controlling valve 36a and torque motor 13a
for controlling the threading of nut 11a on stud 12a. Thus, if for
any reason the torque applied by air motor 13a between nut 11a and
stud 12a does not reach the seating torque 50 to energize the relay
74 of the second control 40a, coil 74a of control 49 is prevented
from energizing the high pressure valve solenoid 34a whereby each
of the controls maintains the threading means in the low pressure
condition until such time as the problem is rectified and all nuts
are properly seated to permit initiation concurrently of the high
pressure setting operation by each of the air motors. As will be
obvious to those skilled in the art, any number of such threading
devices and similar controls 40, 40a (etc.) and 28, 28a (etc.) may
be utilized in parallel for setting a corresponding number of
cooperating threaded elements by means of the common pressurized
air support 29.
The use of the high and low controls at torques 50 and 55 provides
an indication functioning which may not be required in a particular
installation. The primary functioning of the control is to provide
a two-step seating and setting operation for improved accurate
setting of the threaded members to the preselected torque. The use
of the high and low limit lamps and/or recording apparatus as
desired, provides a fault indication functioning which is
supplementary to the basic threading functioning of the
control.
When the nuts are seated on the studs, the control causes a
discontinuation of the torque application, as shown at 49 of FIG.
4, so as to eliminate kinetic energy in the spindle 14 to permit
accurate final setting of the nuts in the high pressure operational
phase. As the high pressure torque phase provides a slow buildup of
the torque, a time expansion occurs permitting conventional low
cost solenoid valves and control elements having appreciable time
delays to be used without substantially adversely affecting the
accuracy of the final setting torque. If desired, a further signal
lamp 83 may be energized by switch 72c when relay coil 72a is
energized to indicate the reaching of the desired preselected set
torque 54.
As will be obvious to those skilled in the art, if desired, the
control 40 may be arranged to permit independent complete threading
operations wherein the setting of the nut and subsequent setting
thereof are effected independently of the seating and setting of
the other nuts by the other air motors.
The foregoing disclosure of specific embodiments is illustrative of
the broad inventive concepts comprehended by the invention.
* * * * *