Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND AND SUMMARY
This invention relates generally to improvements in
fluid dispersing apparatus and methods of applying fluids to
precise locations of hollow objects utilizing centrifugal
force. One application of the invention is the application of
liquid to the internal threads of a fastener nut.
Various coatings of fluid materials are applied to the
internal surfaces of hollow objects such as nut type fasteners
by a variety of coating systems. For e~ample, "Teflon"
(trademark of E. I. DuPont de Nemours & Co.) sealant is applied
to the threads of nuts in order to provide an improved seal.
The presence of the Teflon compound interferes with subsequent
plating or surface coating if the Teflon is leaked onto the
e~terior surfaces.
For example, Teflon coated fasteners are used
e~tensively in the automotive industry where steel parts are
commonly immersed and coated with an electrodeposited rust
inhibitor. A Teflon coating prevents the rust inhibitor
solution from adhering to selected surfaces where the rust
inhibitor layer may interfere with subsequent assembly
requirements. For example, it is often desirable to maintain
internal threads of fasteners free of the rust inhibitor to
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provide more reliable fit-up and assembly. Fasteners which
have a Teflon coating on their internal threads can be immersed
into a rust inhibitor bath along with an entire automotive
assembly while maintaining selected surfaces where the rust
inhibitor will not adhere. This is accomplished without the
use of previous labor intensive, and often ineffective rubber
plugs. In subsequent assembly, the Teflon coating readily
yields to the insertion of a mating external thread.
The process of the present invention teaches coating
on a repetitive part basis to pre-selected surfaces, such as
the threaded cavities of nuts, and avoids contamination of
adjacent and exterior surfaces. The apparatus for practicing
the described process uses substantially all of the material to
coat the nut, thereby eliminating waste.
U.S. Patent 4,652,468 to Gould, et al. discloses a
process for high pressure impact coating of portions of work
pieces such as threaded openings and fasteners and avoidance of
contaminating portions of the work piece with the coating
material. The process requires masking of the surfaces of the
nut in order to restrict material from contaminating the outer
surfaces of the nut. Additionally, the machine requires a
choked area for sucking the waste material from the fastener.
Illustrated preferred embodiments of the present invention
provide a precise amount of material to selected surfaces of
the nut and eliminates the need to suck waste material from the
nut.
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_ U.S. Patent 4,528,938 to Nevel discloses a rotary work
piece treating apparatus for depositing coating or adhesive
materials within threaded fastener nuts. The device includes a
continuously rotating turntable assembly having a plurality of
work station cylinders attached thereto. A probe attached to
the plunger is caused to enter within the internal bore of the
nuts and release flowable material within the nut. The flow of
such material is controlled by a valve stem protruding from the
probe which is depressed against the stop surface when the
probe is inserted within the nuts. Certain preferred
embodiments of the present invention utilize straight line
feeding and eliminates the valve stem control for the
material.
Other prior art such as U.S. Patents 4,060,868 to
Axvig and 3,896,760 to R. J. Duffy disclose systems and methods
for coating the interior surfaces of pipes using a low pressure
application of dry resin material to the interior of heated
pipe sections. These disclosures do not address the problem of
controlling the flow of liquid material to a selected surface
with precise isolation from portions not to be coated with the
liquid material.
Accordingly, it is an object of the present invention
to provide an improved method and apparatus for applying a
precise liquid coating to predetermined selected surfaces of
hollow objects utilizing centrifugal force to disperse a
metered quantity of fluid material.
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_ It is another object of the present invention to
rapidly apply fluid coatings to objects utilizing centrifugal
force from the rotation of a probe inserted into the hollow
cavity of an object.
It is another object of the invention to provide a
process and apparatus which will eliminate waste material,
thereby reducing material costs and ultimately disposal costs
for the waste material.
It is another object of the invention to provide an
apparatus and process for coating objects which will reduce
production and maintenance labor.
It is another object of the invention to provide an
apparatus and process which will eliminate utility costs,
particularly the volume of air needed in the coating process.
It is another object of the invention to provide a
process and apparatus which eliminates the need for sealing
and/or masking of the object to be coated.
It is another object of the invention to provide a
process and apparatus which can control the coating process by
calculating the metered pumping rate, and the up and down cycle
of the probe.
It is another object of the invention to provide an
apparatus and system which applies a uniform coating to a
precise portion of the object to be coated.
It is another object of the invention to provide a
system which recirculates the coating mater~al thereby
restricting settlement problems in the material.
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_ It is another object of the invention to provide a
machine which reduces noise, spillage, and other problems in
the work place.
It is another object of the invention to eliminate
high pressure delivery lines for coating objects.
Additional benefits and advantages of the present
invention will become apparent to those skilled in the art to
which this invention relates from the subsequent description of
the preferred embodiments in the appended claims, taken in
conjunction with the accompanying drawings.
The above objects are accomplished with the apparatus
and process for coating hollow objects with fluid materials
according to this invention. The apparatus and process
described herein utilizes centrifugal force to disperse fluid
from a probe. The apparatus meters a precise amount of fluid
thereby eliminating waste of excess material and the need to
mask the article. Preferred embodiments of the present
invention incorporate a conveying device for moving a
succession of workpieces, for example, internally threaded
articles, into position for application of fluid. In certain
preferred embodiments, a rotating hollow probe is then moved
from under the object into a coating position. Preferably, the
probe is simultaneously moved upward through the workpiece
coating the object as the material is pumped from a holding
chamber through the metering pump, thereby metering the volume
of fluid, and dispersed by the centrifugal force from the
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rotary motion of the probe. In certain preferred embodiments,
when the selected area has been coated, the pump is reversed to
pull the material away from the opening in the probe and the
probe is then withdrawn from the object. In preferred
embodiments, the probe dispenses a second coating during the
removal from the object. The object is then preferably moved
into a drying chamber where the excess vapors are drawn off
from the object. The process minimizes any waste material thus
improving the environmental aspects of the work place.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a fragmentary sectional view of the
apparatus used in the process of coating the objects with
fluid.
Figure 2 is a diagrammatic view of the coating
apparatus.
Figure 3 is a fragmentary sectional view of another
preferred embodiment of the apparatus used in the process of
coating the objects with fluid.
Figure 4 is a top view of the embodiment shown in
Figure 3.
Figure 5 is a cross-sectional view of the rotary probe
in the embodiment shown in Figure 3.
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DETAILED DESCRIPTION OF THE INVENTION
In figure 1, fastener nuts 2 are being coated with a
material such as Teflon fluid material. The nut is delivered
to the coating position by a straight line feeding means. One
embodiment uses a support track moving the nuts to the coating
position. The nuts are loaded onto the feeding means by a
rotary bowl feeder. Any conventional object feeding means is
appropriate.
Spring detent 12 holds a nut 2 in position for
coating. Arrow 60 designates any conventional plunger means to
move the rotary probe 70 into the internal cavity of the nut.
In a preferred embodiment a lead screw drive means (not shown,
but designated by arrow 60) moves the probe 70, motor 82, and
the supporting brackets uniformly upward so that the probe is
inside the cavity of the object to be coated. Since probe unit
79 is driven by belt 73 the entire unit 80 must be moved so
that the probe 70 is within the cavity of the object to be
coated. Lead screw drive means is one example used as a
plunger means 60. Any type of vertical drive means 60 could be
used or alternatively only probe 70 could be moved into the
cavity of the nut if a different apparatus is used to rotate
probe 70.
A portion of table 15 is shown with opening 16 in a
bottom section. Table 15 includes side support 17 which works
in conjunction with spring detent 12 to hold nut 2 in
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position. Table 15 can also support the feedinq means, drying
means, plunger means 60, and computer 50.
Referring to Figure 3, in another preferred embodiment
of the present present invention, conventional microlab
metering pump 75 is utilized to provide precise control over
the volume of fluid introduced into rotary probe 170. A
relatively narrow hollow stainless steel tube 30, on the order
of 0.083 inches in outside diameter and 0.062 inches in inside
diameter, is connected to the fluid supply through pump 75.
Top end 32 of tube 30 is preferably positioned in hollow cavity
180 of probe 170 up to a distance approsimately 0.032 inches
below opening 176 in rotary probe 170. The small diameter of
tube 30 provides better control of fluid presentation to rotary
probe 170 and minimizes the volume of fluid necessary to
prefill the system.
In the embodiment shown in Figure 3, clamp 100 fixedly
secures probe 170 to housing assembly 102. A pair of
conventional bearings 95, driven by belt 73, provides rotation
of probe 170 and housing assembly 102. Tube 30 is connected to
pump 75 and therefore does not rotate. Second housing 35 is
fixedly attached to tube 30 and includes cavity 36 for
capturing fluid and solvent which runs downwardly into the
space caused by clearance between tube 30 and internal cavity
180 of probe 170.
Referring to Figure 4, a slideably mounted
presentation pin 20 is positioned over internal cavity 19 of
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fastener 8 and moves vertically downwardly into internal cavity
19 of the ne~t fastener 8 to be coated. Once inserted, the
presentation pin 20 moves fastener 8 horizontally along
direction 6 and positions the fastener 8 into the position of
fastener 4 centered over rotary probe 170. Positioning spring
22 engages fastener 4 securely against side support 17 to
position internal cavity 19 of fastener 4 in the proper
position for the coating process. The width between side
support 17 and positioning spring 22 is transversely adjustable
to accommodate fasteners 4 with different outside diameters
while maintaining alignment between internal cavity 19 of
fastener 4 and probe 170.
Referring to Fig. 5, rotary probe 170 is shown. Probe
170 preferably has shaft section 172 which transitions into
cylindrical section 174 of smaller diameter than shaft section
172. Preferably, at least one opening 176 is provided in the
vertical portion of cylindrical section 174 to allow for
centrifical dispersion of the fluid therethrough. Although it
is not necessary for the non-pressurized fluid coating system
of the present invention, cap 178 preferably encloses the top
of probe 170. Tube 30 enters into hollow cavity 180 of probe
170 and transfers fluid into a position for centrifical
dispersion through opening 176. In a preferred embodiment, two
0.20 inch diameter openings 176 are utilized in probe 170.
Shaft section 172 with an outside diameter of appro~imately
0.125 inch and cylindrical section 174 with an outside diameter
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ranging from 0.070 inch through 0.125 inch has proven to be
effective in coating internal cavity 19 of fasteners 4 with
inside diameters ranging from approximately .125 inch to .500
inch.
In the preferred embodiment shown in Figure 3, tube 30
is prefilled with fluid pumped from metering pump 75. Once the
capacity of tube 30 is exceeded, the excess fluid runs out
opening 176 and proceeds into purging chamber 128. This
initial overflow of fluid permits air and other impurities
which may be present in the fluid remaining in tube 30 to be
replaced with clean fluid drawn from Teflon tank 85.
During the solvent cleaning cycle, selector valve 118 is
reset to draw solvent from solvent tank 125 into tube 30.
Again, once the drawn solvent exceeds the capacity of tube 30,
the excess solvent runs out opening 176 and proceeds into
purging chamber 128. The fluid and solvent in purging chamber
128 is tranferred through line 119 into waste container 127.
Once the solvent purge cycle is completed, selector valve 118
is again reset to draw from Teflon tank 85 and Teflon fluid is
again prefilled into tube 30 as described above. Once this
Teflon fluid prefill cycle is complete, the system is again
ready to apply Teflon fluid coating to internal cavity 19 of
fastener 4.
In certain preferred embodiments, stepping motor 82 is
programmable through digital computer 50 to control the rate
and extent of vertical travel of rotary probe 170. Preferably,
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once fastener 4 is in the proper position to initiate the
coating process, stepping motor 82 moves rotary probe 170
fairly rapidly to a position immediately below the top surface
14 of table 15. At this point, the vertical travel is
momentarily stopped. During the momentary stoppage, metering
pump 75, controlled by digital computer 50, begins to pump
fluid through tube 30. Rotary probe 170 then continues
vertically upwardly at a pre-selected coating travel speed
through internal cavity 19. Once the coating operation has
been completed, rotary probe 170 can be withdrawn from internal
cavity 19 fairly rapidly to a position below the top surface 14
of table 15 to allow the next fastener 8 to be positioned for
coating.
In most applications, rotation of probe 170 at a rate
of appro2imately 10,000 revolutions per minute has proven
effective in providing sufficient centrifical force to disperse
Teflon fluid from probe 170 onto the selected portions of
internal cavity 19. The optimum revolution rate varies
somewhat with the viscosity of the fluid being dispersed. For
example, a slight increase in rotation can often be effective
when dispersing fluids with higher viscosities.
In certain preferred embodiments, metering pump 75 may
be initiated when opening 176 in rotary probe 170 is positioned
at any pre-selected vertical position below or above top 14 of
table 15 in interior cavity 19 of fastener 4. Therefore, the
position of initiating fluid flow can be input via digital
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computer 50 to begin below top 14 of table 15 prior to opening
176 entering internal cavity 19, to ensure complete thread
coverage. Alternatively, the coating can begin at any
pre-selected level above top 14 of table 15 in internal cavity
19 of fastener 4 for coating of only selected portions of the
length of internal cavity 19.
In certain preferred embodiments, rotary probe 170
spins continuously, and the dispersion of fluid is controlled
by metering pump 75 pumping fluid above the level of opening
176 in rotary probe 170. The total volume of fluid dispersed
can be pre-selected by entering the number of steps of metering
pump 75 via digital computer 50. To discontinue coating,
metering pump 75 is stopped and no further fluid is present at
opening 176. Therefore, no further fluid dispersement occurs.
In most applications, the volume of fluid dispersed is selected
to provide a Teflon coating of approsimately .001 inch on those
surfaces to be coated. By control of metering pump 75 and
vertical coating travel speed by digital computer 50, a uniform
coating of Teflon is achieved, even on uneven surfaces such as
threads. By programming digital computer 50 and control of
metering pump 75, internal cavity 19 of fasteners 4 can be
completely coated or alternatively only preselected portions of
the length of internal cavity 19 may be coated.
Simultaneously a digital computer 50 controls the
movement of the nut positioning means (not shown), the vertical
plunger means 60, (illustrated by the arrows), and the pump 75
providing fluid.
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_ When the apparatus is activated, unit 80 is programmed
to automatically move into a position until probe 70 contacts
a photo electric sensor 78 located near table 15. The computer
50 is then programmed to define the position where probe 70
begins coating a nut 2.
In preferred embodiments, photosensitive electric eye
24 verifies that fastener 4 is in the proper position for
coating before allowing probe 170 to enter internal cavity 19
of fastener 4. If fastener 4 is not positioned in a suitable
position for coating, digital computer 50 will prevent rotary
probe 170 from dispersing fluid. This prevents inadvertent
dispersion of fluid when internal cavity 19 of fastener 4 is
not in the proper position for coating. A counter mechanism
(not shown) may also be included to track the number of
fasteners 4 coated.
Unit 80 includes replaceable unit 79 made up of probe
and pulley section 79. This portion of the machine is
easily disconnectable in order to provide a different tip for
different types of fluids to coat different objects. The
pulley diameter is constructed for the specific type of fluid
to be dispersed. This provides an easy control for the
operator to change from one fluid to another.
The pulley 72 is connected via a belt 73 to a pulley
74 connected to a motor 82. The speed of the motor 82 can be
controlled by the computer 50. In a preferred embodiment, the
probe is continually rotating while the apparatus is
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operating. A recirculating pump 112 pumps well stirred fluid
from Teflon tank 85 continuously through supply line 114 in
order to keep the coating fluid from possible segregation.
When pump 75 is connected to supply line 114, fluid moves
through selector 118, into mi~ing valve 86, then through
positive displacement metering pump 75. A metered amount of
fluid is delivered through delivery tube 71 in rotary union 90
to rotating probe 70. Rotary union 90 allows probe 70 to turn
during the delivery of fluid. Conventional bearings 95 are
shown at a suggested location in rotary union 90.
As seen in figure 2, a separate additional fluid in
fluid #2 tank 105 can be introduced into mixing valve 86
through line 110 by conventional valving means when a two
component fluid mixture is desired. Computer 50 controls valve
86 for such a mixture. Computer 50 controls the metering pump
rate, the distance and speed of the plunger means 60, and the
operation of the selector valve 118.
The pump 75 moves fluid into the probe 70. The pump
does not disperse the fluid out of opening 76. The fluid is
dispersed by the centrifugal force of the probe rotating. In
other words pump 75 simply positions fluid to a level from
which the rotation of the probe forces the fluid out the
openings. In preferred embodiments rotating the probe at
speeds between 10,000 and 15,000 revolutions per minute have
been particularly effective to utilize centrifugal force to
disperse the fluid.
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_ Computer 50 can be programmed to coat the material
while traveling upward through the nut and then recoat the nut
during removal from the nut. The use of the probe and location
of the opening provides the nut to be coated in precise bands
within the internal cavity 19. For esample, the coating can
start at 2 centimeters from the bottom of the nut and end 4
centimeters form the top of the nut by programming the computer
for this band of coating.
When the coating operation is one coat in only one
direction, preferred embodiments use a reversible pump to pump
material back to supply chamber 85. When pump 75 is reversed
it pulls material back into the supply chamber and allows the
probe to continue spinning without dispersing fluid. The probe
would stop dispersing fluid without reversing the pump.
However, the reversing of the pump pulls material away from the
discharge opening to ensure material will not be inadvertently
dispensed.
Diagramatic view 2 illustrates the use of Teflon
material in a system utilizing two coating machines controlled
by one computer. Recirculating pump 112 is connected to a
supply of fluid 85, for example, Teflon. This recirculation of
fluid mixes the material and restricts settlement of components
from the mixture. Selector valve 118, controlled by computer
50, is open to either supply line 114 allowing Teflon from tank
85 or line 115 allowing solvent from tank 125 into the mising
valve 86. Teflon is selected for coating the nut. Solvent is
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selected for purging of the system prior to a process shutdown
for a variety of reasons including but not limited to
maintenance or changing to a different nut size. To ensure
consistent, high quality coating, the solvent purge cycle
should preferably be utilized at least once during each four
hour period in which the equipment is operated.
Computer 50 is a programmable computer allowing the
operator to provide pumping speed rates of material to be
pumped and the location of the probe within the article to be
coated. It may be appreciated that the operator can easily
program the computer while observing the coating operation.
The speed of vertical travel of plunger means 60 can be
controlled to provide for different viscosities of fluids and
the desired thickness of the coating. Stepping or servo motors
can be connected to the motor 82 in order to provide precise
control of the operation.
Figure 1 shows the fluid chamber 71 leading to the
probe 70. In this preferred embodiment, the opening 76 for the
dispersion of material is on or near the top of the probe 70.
It can be appreciated that as the probe rotates, the coating
material will be discharged from the top of the probe. The
material in the probe forms a parabolic configuration. If the
material is not near the upper portion of the probe, the
material will not be discharged from the opening 76.
A conventional vapor discharge means (not shown) is
provided after the nut has received the coating fluid and moved
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through a drying chamber (not shown). The drying chamber can
use heated air forced through a closed chamber by a fan.
In another preferred embodiment, a drying track (not
shown) is utilized to ensure that the Teflon coating is dry
before fasteners 4 are dropped into a storage or shipping
container (not shown). Preferably, a drying track containing
forced air heated to approximately 120F is used with a track
length sufficiently long to ensure complete drying of the
Teflon coating before the fasteners reach the end of the line.
It should be recognized that the temperature and length of the
drying track may be readily adjusted to accommodate fluids with
different drying characteristics.
Preferred embodiments of the present invention reduce
the waste material. A preferred embodiment provides a purging
chamber 128 whereby the material in the system can be shut off
at valve 118 and the material left can be discharged into a
waste container 127. The solvent remains in fluid chamber 71
until a pre-filling operation forces the solvent into purging
chamber 128 and fills fluid chamber 71 with Teflon. The waste
material flows from purging chamber 128 through line 119 into
waste container 127.
Certain preferred embodiments of the present invention
utilize one computer 50 to control two production lines. The
computer is programmable to provide one coating application on
one head and a distinct coating application on the other head.
Several "lines~ could be controlled by one computer. The use
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of the computer allows precise bands of fluid to be dispersed
within the hollow object.
Preferred embodiments of the present invention may be
used to coat objects with any flowable material. For example,
an extremely fine flowable Teflon material is contemplated for
use with this invention. Also, a material such as
microencapulated epo2y such as that sold under the trademark
Scotchgrip by Minnesota Mining & Manufacturing Co. or
microencapulated anarobic epoxy such as that marketed by Lock
Tite Corporation may be readily applied to the internal
cavities of fasteners using this invention. Also, fluid weld
spatter repellant may be applied to selected internal cavities
using this invention. Preferred embodiments of the present
invention are also capable of coating non-circular internal
cavities in fasteners without any change in the equipment
set-up.
While the above description constitutes the preferred
embodiments of the present invention, it will be appreciated
that the invention is susceptible to modification, variation
and change without departing from the proper scope and fair
meaning of the accompanying claims.
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