BACKGROUND OF THE INVENTION
The present invention generally relates to improved discrete
parts, such as fasteners, having a useful barrier coating applied to a portion thereof
and a method and apparatus for processing such parts with a coating material. More
particularly, the invention relates to the deposition of liquid fluorocarbon or
hydrocarbon type coating materials in a precise and continuous high speed manner
onto selected surfaces of fasteners to form a masking insulating and/or lubricating
barrier coating on the fasteners. A particular application of the invention is the
application of liquid fluorocarbon coating material to the internal threads and
possibly other surfaces of an odd shaped nut having a deep threaded central hub.
Metal parts such as fasteners are being increasingly exposed
to electrodeposition paints, primers, and corrosion resistant materials. Recent
advances in improving the corrosion resistance of automobile bodies and other like
structures have made use of such formulations for the treatment of steel structural
members standards in industry. Many.fastening elements are attached to basic structural
components prior to processing of such components with electrodeposited primers,
paints, and rust inhibitors. Therefore, any exposed threads of the fasteners attached
to such components may become contaminated and make it difficult or impossible to
thread such exposed fasteners with a mating fastener for subsequent assembly. Any
coatings applied to such fasteners to resist contamination must also be sufficient
to resist splatter from the welding procedures that they may be exposed to as they
are affixed to the structural components. The need, therefore, arose to develop
a way of preventing contamination of these exposed fastener threads that would not
substantially interfere with the ultimate performance of such fasteners.
The prior art proposed a variety of coating systems to
attempt to solve the problem of resisting corrosion inhibitor build-up on the threads
of fasteners. However, these prior coating systems all suffered from substantial
drawbacks even when used to coat standard types of fasteners. This has led to the
development of improved coating methods and apparatus utilizing liquid fluorocarbon
coating materials, such as described in US 5679160. Such new systems feature capabilities
that have caused demand for such coatings on a wide variety of different types of
fasteners and other discrete parts to continue to increase. The expanding popularity
of such coatings has further compounded the challenges facing existing coating systems.
For example, there has been increasing demand in industry
for providing coatings on various odd shaped fasteners to resist the build-up of
electrodeposited paints, primers, and corrosion resistant materials. These fasteners
include, for example, internally threaded fasteners with extended hub sections,
internally threaded fasteners with rounded lead in sections between the top surface
of the fastener and the threaded portion, fasteners having off center openings and
fasteners that have significantly different top surfaces than bottom surfaces.
Further compounding the difficulties of depositing a suitable
barrier coating on such fasteners has been an increase in the need to cover not
just threaded portions of such fasteners, but also all or a portion of other surfaces
such as lead in sections or top or bottom face portions of the fastener at the same
Specifications requiring such extended coating coverage necessitate very precise
control so that only certain predesignated portions of the threads and additional
parts of the fastener are coated while the remainder of the fastener remains free
of such barrier coatings.
The vast majority of prior art systems are incapable of
accommodating irregular types or shapes of fasteners or achieving the coating of
a combination of fastener surfaces described above. U.S. Patent No. 4,842,890 to
Sessa et al. discloses a method for coating fasteners with a powdered fluorocarbon
material. This method, however, is restricted to coating fasteners that have a head
and shank portion and cannot accommodate either internally threaded fasteners or
odd shaped fasteners.
U.S. Patent No. 4,652,468 to Gould et al. discloses a process
for high pressure impact coating of threaded openings of internally threaded fasteners
with fluorocarbon materials such as Teflon®. The Gould process attempts to
specifically avoid the deposition of coating material on any surfaces of the fastener
other than the threads. The process requires a masking of the surfaces of a nut
in order to restrict the coating material from being applied to any other surfaces
of the nut.
This process is complicated and expensive because it requires
a choked area for drawing in the excess coating material from the opening of the
nut and necessitates indexing, masking, and removing excess material during the
coating process in a manner that significantly slows processing speeds. Additionally,
Gould does not teach a way of accommodating any odd shaped internally threaded fasteners.
U.S. Patent No. 4,701,348 to Neville discloses a method
of coating the threads of internally threaded fasteners. Neville requires a metering
nozzle to be selectively introduced and removed from a succession of internally
threaded fasteners. The reciprocating movement of the nozzle necessitates an indexing
fasteners that stops the flow of fasteners each time coating material is being applied
to any single fastener. This dramatically slows processing rates. '
The Neville nozzle has an ultrasonic tip which is vibrated
after the metering of a drop of coating material in order to explode the drop to
cause a fine mist of the fluid suspension to be sent towards the threads of the
nut. Due to the difficulty in metering identically sized drops and successions exploding
in the exact same manner using an ultrasonic power source. This system often exhibits
uneven coating of the fasteners. Additionally, the flat, continuous belt and nozzle
construction of Neville do not allow odd sized fasteners to be processed, nor is
the coating of any portion other than the threads of the fastener contemplated.
Published PCT International Application WO8906757 of Prittinen
et al. discloses a method and apparatus for coating internally threaded fasteners
with materials such as Teflon®. This invention provides an indexed flow of
fasteners before an application device that introduces a reciprocating rotary probe
into each fastener to be coated. In addition to being slow because of the indexing
required, this device does not contemplate application of Teflon® materials
to any surfaces other than threads the fastener. This system also lacks a supporting
structure that can readily and easily accommodate various different types of odd
Furthermore, most of the prior art systems identified above
require post application heat treatment of the coated fasteners, such as by baking
in an oven. None of these references describes any type of on-line device or method
for efficiently and simply moving the coated fasteners from the application conveyor
to a post application heating station, such as an oven. Instead these systems deposited
coated fasteners into bins or racks which then had to be physically brought to an
oven and manually unloaded. As can be readily appreciated, this process was very
It is, therefore, apparent that a need exists in the art
for an improved apparatus and method of coating the threads and/or other portions
of a wide variety of fasteners to prevent electrodeposition of paints or corrosion
resistant materials and for an improved on-line system of transferring coated fasteners
into a post application heating station.
U.S. Patent 5403624 discloses a method and apparatus for
coating a fastener with head and shank portions. The invention includes the steps
of an apparatus for transferring the fasteners from a feed mechanism such that the
fasteners are positioned for coating. The fasteners are then conveyed through a
plurality of operating stations, beginning with a heating station where the shank
portions of the fasteners are heated. Subsequently, at a material applying station,
a coating material is applied to the heated shank portions. A preferred embodiment
of the method and apparatus of the present invention includes using a magnetic holder
to carry the fasteners horizontally by their head portions, where fasteners are
centred by a rotating wheel, heating the shank portion to a temperature above the
melting point of the applied material and applying the material to the heated shank
portion to form a coating thereon. The magnetic holders are part of an endless travelling
belt that rotates continually. The fastener carriers have teeth that engage a rack
to rotate the fasteners. A conveyor provides added air cooling for the coated fasteners,
which can continue to be rotated. Also disclosed is a transfer wheel with two sets
of notches that is synchronously coupled to the travelling belt for placing and
aligning fasteners on the belt for coating. Uncoated areas on the fasteners may
be detected via sensors present beyond the powder spray station which may include
a plurality of spray nozzles.
SUMMARY OF THE INVENTION
It is, therefore, an object the present invention to provide
an improved apparatus for the application of liquid masking, insulating and/or lubricating
substantially pinhole free barrier coatings on discrete objects, such as fasteners,
that overcomes the problems posed by prior art systems.
It is a further object of the present invention to provide
an improved method and apparatus for providing a barrier coating on threaded or
other surfaces of a succession of fasteners does not require the stopping of the
feed of fasteners as they travel through the coating apparatus.
Another object of the present invention is to provide an
improved method and apparatus for providing a barrier coating on the threaded or
other surfaces of a fastener that features precise metering and control of the location
of the deposition of the liquid material applied to the fastener.
Still another object of the present invention is to provide
an improved method and apparatus for the application of a barrier coating onto the
selected portions of fasteners that requires little or no preheating of the fasteners.
A still further object of the present invention to provide
a method and apparatus for the application of a barrier coating of liquid material
onto the threads of an internally threaded fastener that does not require a nozzle
to be introduced into the threaded opening.
It is another object of the present invention to provide
a method and apparatus for the application of a barrier coating onto the threads
and/or other surfaces of fasteners that accommodates a wide variety of different
types, sizes, and shapes of fasteners.
It is a further object of the present invention to provide
a method and apparatus for the application of a barrier coating of liquid material
onto a fastener that further provides an on-line mechanism for transferring the
fasteners directly into a post application heat treatment device, such as an oven.
It is also an object of the invention to provide a method
and apparatus for coating the threads or other portions of the fastener with a barrier
coating at productions rates far faster than those obtainable in the
Yet another object of the present invention is to provide
a method and apparatus for coating the threads of a fastener with a barrier coating
that does not require rotation of the material applying element during the coating
It is yet another object of the present invention to provide
a method and apparatus for coating fasteners with a barrier coating material that
can easily accommodate either fasteners fed loosely or in a regularly spaced centered
The invention provides an apparatus for applying masking,
insulating and/or lubricating coating material on selected portions of a plurality
of fasteners, the apparatus comprising first continuously moving conveying means
for supporting said fasteners, means for introducing said fasteners onto said first
conveying means, applying means for applying coating material onto each of said
fasteners, said applying means being substantially centered over said first conveying
means, and optical sensing means located along said first conveying means, characterised
in that the applying means is an airless spray means for selectively applying atomized
liquid coating material onto a predetermined portion, each of said fasteners, and
in that the optical sensing means is in communication with said applying means for
sensing when a fastener is present before said applying means and for triggering
said applying means to cause said applying means to apply the coating material onto
said predetermined portion of each fastener.
The invention also provides a method of applying masking,
insulating and/or lubricating coating material onto selected portions of a plurality
of fasteners, the method comprising the steps of providing a first continuously
moving conveying means for supporting one surface of the fasteners, introducing
said fasteners onto said first conveying means, and applying coating material onto
said fasteners with applying means, characterised in that the method further comprises,
prior to send applying step, sensing whether a fastener is present along said first
conveying means before said applying means and triggering said applying means to
cause application of an airless spray of atomized liquid coating material onto a
predetermined portion of each of the fasteners.
In one preferred embodiment, individual articles, such
as non-uniform and odd shaped nuts, are deposited onto a continuously moving split
conveyor belt in a spaced uniform orientation. The fasteners are continuously carried
by the conveyor belt at a high rate of speed through a liquid material deposition
area, where optical sensors trigger precisely metered discrete shots and atomized
airless sprays of material onto specific locations of the fastener and/or the threads
of the fasteners in order to form a barrier coating thereon. With the barrier coating
material deposited on the fasteners, they are next conveyed through an optional
cleaning station. The fasteners are then elevated and inverted by use of a magnetic
wheel and subsequently transferred onto a conveyor which carries the fasteners away
from the device and directly into a heated oven in order to stabilize the coating
and vaporize the organic solvent contained in the coating material.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described further in connection
with the attached drawings wherein like reference numbers refer to corresponding
parts throughout, the several views of preferred embodiments of the invention wherein:
DETAILED DESCRIPTION OF THE INVENTION
- Figure 1 is a side view of one embodiment of the present invention.
- Figure 2 is top view of one embodiment of the present invention.
- Figure 3 is a partial cross-sectional view taken along the line 3-3 of Figure
2 of one embodiment of the present invention.
- Figure 4 is a perspective view of an exemplary fastener that can be processed
in accordance with the present invention.
- Figure 5 is a partial cross-sectional view taken along the line 5-5 in Figure
- Figure 6 is a perspective view of an adjusting sensor slide of one embodiment
of the present invention.
- Figure 7 is a perspective view of another exemplary fastener that can be processed
in accordance with the present invention.
- Figure 8 is a top view of another fastener that can be processed in accordance
with the present invention.
While the present invention will be described particularly
with respect to applying fluorocarbon or Teflon® type material to form a continuous
substantially pin-hole free barrier coating on the threads and/or other surfaces
of non-uniformly shaped threaded articles, it is to be understood that the present
invention can be utilized to apply a variety of fluorinated ethylene propylene copolymers
or other similar type materials such as silicones, waxes and petroleum greases.
The present invention contemplates supplying the coating materials in a liquid form
that contains a fine unpolymerized powdered material in an epoxy paint containing
a fluid solvent.
Additionally, while the invention contemplates providing
coatings on a variety of discrete fasteners including, but not limited to, nuts,
bolts and similar articles, it will be described for exemplary purposes only with
reference to a weld or cage nut having a central threaded opening such as is illustrated
in Figures 4 and 5. Also, although the invention will primarily be described in
connection with providing a coating on substantially all of the threads and the
lead in area of a threaded fastener, it is also to be understood that such a coating
could be placed on a limited number of threads and/or be provided on non-threaded
surfaces if so desired.
Figures 1 and 2 generally illustrate one preferred embodiment
of the device 10 for practicing the present invention. The device 10 functions to
achieve the process steps of the present invention. The barrier coating that is
deposited by the device is substantially uniform. When deposited on the threads
of a fastener, the fastener exhibits substantially uniform torque-tension curve
behavior during coupling. The device 10 has a frame 12 that serves as a mounting
base for a split belt conveyor system 14 and an inverting removal system 16. The
removal system 16 is positioned so that one of its ends partially overlaps one end
of the split belt conveyor system 14. The conveyor system 14 features front and
back split style conveyor wheels 18 and 20 respectively that have two continuous
spaced conveyor belts 22 and 24 running therebetween.
This belt construction leaves an open channel 25 between
the two belts 22 and 24 and has been proven to be particularly effective in moving
fasteners such as non-uniform nuts having deep threaded sections along the conveying
system 14. The channel 25 is adjusted to be slightly larger than the outside diameter
of the fastener and allowing the hub 86 to be centered between the belts 22 and
24. An example of such a fastener is indicated generally as 26 in Figures 4 and
5. Prior art single belt systems generally do not provide an adequate means for
accommodating such fasteners, particularly where surfaces other than the threads
of the fastener 26 also were desired to be coated.
The gravity force exerted on each fastener 26 on the conveyor
system 14 tends to hold the bottom surface 87 of the fastener 26 in frictional engagement
substantially flat against the top surface of the belts 22 and 24 causing the fasteners
26 to move continuously along the belt in a stable and fixed manner and at a consistent
speed. No additional devices are needed to attach the fasteners 26 to the belts
22 and 24 during processing. The split belt conveyor system 14 has proven to be
very effective in providing a continuous stream of fasteners 26 in a very consistent
position, thereby enabling coating materials to be applied to the fasteners 26 while
using very high belt speeds.
The conveyor system 14 carries fasteners 26 from a parts
feeder 44 into and past an application station 46. The conveyor system 14 next carries
the fasteners 26 through an optional excess material removal station 69 and an optional
material fixing station 61. The conveyor system 14 then moves the coated fasteners
26 to an inverting removal system 16.
As will be described to follow in detail, the removal system
16 provides a unique on-line mechanism that first utilizes the attractive forces
generated between the fasteners 26 and the magnetic conveyor wheel 34 to remove
them from the downstream end of the belts 22 and 24 at the rear conveyor wheel 20.
As the conveyor wheel 34 rotates, the fasteners 26 are elevated and subsequently
inverted so that they are resting on their top surfaces 78 along a conveyor belt
68 moving in a direction opposite their original direction of travel when they were
on the split belt conveyor system 14.
The fasteners 26 are subsequently removed from the conveyor
belt 68 and are directed onto an additional conveyor 94 that moves the coated fasteners
26 away from the device 10 and directly into a heat treatment station such as an
oven. The elevation and inversion of the coated fasteners 26 and direction of those
coated fasteners onto a conveyor 68 that takes them away from the device 10 and
directly into a heating system such as an oven all occurs in an on-line continuous
fashion and does not require indexing or slowing of the split belt conveyor system
A preferred embodiment of the present invention will now
be described in detail by tracing the path of fasteners 26 through the device 10
with reference to Figures 1-6. This embodiment of the present invention will be
described for exemplary purposes only in connection with fasteners such as cage
or weld nuts that have a deep threaded central hub 86 as illustrated in Figures
4-5. As previously described, cage or weld nuts having a diamond or rectangular
top surface and/or an off center opening, as illustrated in Figures 7-8, are likewise
Referring particularly to Figures 1-2, the fasteners 26
to be processed by the device 10 are first ordered and aligned in a uniform orientation
by a parts feeder 44. The parts feeder 44 can take many different forms that are
well known in the art such as vibratory feed bowl mechanisms. Alternatively, the
fasteners could be fed by hand to the split belt conveyor system 14. Once sufficiently
ordered and aligned, the fasteners 26 are exited from the feeder 44 onto a track
96 that provides an angled delivery onto the conveyor system 14. The track 96 has
a central gap 97 and two spaced rails 98. The gap 97 allows the enlarged hub 86
of the fasteners 26 to project below the surface of the rails 98. The rails 98 provide
a support surface for the bottom 87 of the fastener top surface 78.
As mentioned above, the split belt conveyor system 14 has
front and rear split style conveyor wheels 18 and 20 respectively that are mounted
to the frame 12 of the device 10. The conveyor system 14 has two continuous conveyor
belts 22 and 24 that run between the wheels 18 and 20 and provide a channel 25 between
the belts 22 and 24. The wheels and belts can be readily removed from the device
10 and changed to enable the device 10 to accommodate different types of fasteners
26. Additionally, the width of the channel 25 between can be adjusted by either
spreading the belts 22 and 24, or moving them closer together. The conveyor system
14 also provides blocks 28 spaced along the underside of the top surface of the
belts 22 and 24 to provide support thereto and to maintain the belts 22 and 24 substantially
straight and parallel to the frame 12 while conveying fasteners 26 from one end
of the device 10 to the other.
The belts 22 and 24 can be constructed of a number of different
materials, provided that they exhibit high strength and provide a non-stick surface.
A particularly preferred material for the belts 22 and 24 has been found to be a
stainless steel that is approximately .625" wide and approximately .032" - .050"
thick. As can readily be appreciated, belts having many different thicknesses and
widths can also be utilized depending upon the particular fastener to be processed
by the present invention.
A variable speed motor (not shown) is connected to the
drive wheel 18 respectively and allows the speed of the belts 22 and 24 to be selectively
adjusted to a desired consistent speed. Alternatively, the motor could also be connected
to wheel 20. Depending upon the type of fasteners processed, the practical belt
speed usually ranges from about 6 to about 30 feet/minute. These belt speeds enable
production of 3,000 to more than 10,000 parts/hour by the present invention, depending
upon the part, its shape and size.
As the fasteners 26 continue to move down the conveyor
system 14 they next encounter an application area 46. The application of all liquid
materials to the fasteners 26 is accomplished in the area 46. It is occasionally
preferred to provide an optional heater along the conveyor system 14 to preheat
the fasteners to about 100°F to 150°F prior to the application of any
liquid materials. In certain limited instances, such preheating of the fasteners
26 may assist in the distribution of liquid material applied to the fasteners 26.
An accessory rail 30 is mounted to one of the support blocks 28 to provide a point
of attachment for the various components in the application area 46.
Prior to coating the fasteners 26, it is sometimes necessary
to loosen surface oil or dirt from the threads 80 or other areas prior to any coating
operation. To accomplish this purpose, as the fasteners 26 travel into the application
area 46, they first encounter an optional on-line cleaning station referred to generally
The cleaning station 47 provides one or more guns such
as gun 50. The gun 50 is mounted on a stage 48 that is capable of adjustment in
at least two'and preferably three different axes. This enables precise adjustment
of the gun 50 to accommodate a wide variety of different types of fasteners 26 or
other parts. The stage 48 is mounted at one end to the accessory rail 30. In certain
preferred embodiments, the stage 48 is adjustable in only two axes - vertically
and closer or further from the part. In this case, the optical sensor 53 described
in detail below is mounted to the block 100 of an adjustable slide 102 as illustrated
in Figure 6. The base 106 of the slide is in turn connected to the rail 30. Side
to side adjustment is then accomplished by turning the screw 104 to move the block
100 and sensor 53 connected thereto. Alternatively, multiple slides 102 could be
stacked together to provide two or three axis adjustment.
Although a variety of different guns can be utilized for
the purpose of metering precise high speed discrete shots of liquid material, a
particularly preferred gun has been found to be a Nordson® Zero Cavity gun
with a Number 276515 module manufactured by the Nordson Corporation of Norcross,
Georgia. Again, although a variety of different stages can be used, a particularly
preferred stage has been found to be the 4500 Series ballbearing stage manufactured
by the Daedal Division of the Parker Corporation of Harrison City, Pennsylvania.
The gun 50 is supplied with solvent from an off-line supply
container (not shown). An optical sensor 53 is mounted to the rail in close proximity
to gun 50. When the sensor 53 senses threads 80 or another predetermined portion
of the fastener 26, it triggers a discrete shot of an appropriate type of rapid
evaporating liquid solvent to be precisely delivered onto the threads 80 or other
desired surfaces of the detected fastener 26. A particularly preferred sensor for
this purpose has been found to be the model FX7 manufactured by Sunx Sensors Corporation.
An alternative preferred sensor has been found to be the model no. PZ-101 manufactured
by Keyance Corporation. Although a variety of different solvents can be used for
this purpose, a particularly preferred solvent has been found to be methylethylketone
(MEK). Once applied to the fasteners 26, the solvent is given a sufficient time
to loosen any surface oil and dirt that may be on the threads 80 or other surfaces.
The conveyor system 14 next moves the fasteners 26 past
the high pressure air blow off port 54. This port 54 is utilized to blow air into
the threaded hole 80 thereby causing the solvent and loosened dirt and oil to atomize
and be sharply blown out of and carried away from the now clean threads 80 of the
fasteners. After.exiting the cleaning station 47, the fasteners 26 are allowed some
additional time for any solvent remaining on the threads 80 to dry prior to application
of any coating material.
In the alternative, the gun 50 of the on-line cleaning
station 47 can be used to deliver discrete shots of solvent such as N-methyl-pyrrolidone
(NMP) onto the threads 80 or other portions of each detected fastener 26. In this
situation, the blow off port 54 is not used to remove the solvent. Instead, the
air pressure in the blow off port 54 is reduced so that it spreads the solvent evenly
in the threads 80 of the fasteners 26 to act as a wetting agent and improve the
wicking of subsequently applied liquid coating material.
As the fasteners 26 are carried further down the conveyor
system 14, they next encounter a liquid material application station designated
generally as 45. The application station 45 of the present invention is particularly
designed for applying liquid coating materials to fasteners 26 that have odd shapes,
deep threads, extended, threaded portions, off center openings, or are otherwise
particularly difficult to completely or partially coat. The station 45 is also designed
for the application of liquid coating material to surfaces other than the threads
80 of a fastener 26, either alone or in combination with coating the threads 80.
Referring particularly to Figures 1 and 2, as previously
described in US 5679160, one or more liquid applicator guns 58 may be provided for
applying liquid coating material 99 such as a suspension of a fluorocarbon in a
liquid solvent to successive fasteners as they pass by the guns 58. The entire disclosure
of that copending application is incorporated herein by reference. Each of the guns
58 is attached to the accessory rail 30 of the device 10 by means of a stage 56.
The stages 56 allow the guns 58 to be selectively positioned and subsequently be
secured in fixed locations for the application of liquid coating material 99 to
different size or shape fasteners 26.
Preferred stages 56 for use in connection with the present
invention allow adjustment of each gun 58 along three different axes. The stages
56 enable the vertical distance between the guns 58 and the conveyor belts 22 and
24 the horizontal location of the guns 58 in relation to the center of the threads
80 with the angle and direction of the guns 58 with respect to the threaded hub
86 to be adjusted. The stages 56 may be used alone or in connection with one or
more slides 102. Particularly preferred stages, slides and guns for use in connection
with the present invention are the same as those described above in connection with
the on-line cleaning station 47.
Once the fasteners 26 move into the liquid application
station 45, the threaded hub 86 of each of the respective fasteners 26 is detected
by photo-optic sensors 52. Although a variety of different optical sensors are capable
of being utilized for this purpose, it has been found that a particularly preferred
sensor for use in the present invention is the model no. PZ-101 manufactured by
Keyance Corporation. Once the sensor 52 detects the presence of a fastener 26 and/or
the threaded hub 86 thereof, it sends an electrical signal to its respective gun
58 which triggers the firing of a discrete shot of liquid coating material 99 onto
a portion of the threads 80 of each fastener 26. Once deposited, the coating material
99 flows down the threads 80 toward the bottom 83 of each successive fastener 26.
As the fasteners 26 move past successive guns 58, additional
discrete shots of coating material 99 are deposited circumferentially apart from
the location of the first discrete shot of coating material 99 that has been applied
to the fastener 26. By applying the discrete shots of liquid material in this manner,
the material 99 wicks around the threads 80 of the fasteners 26 in a substantially
The location, speed and amount of material 99 that is deposited
is controllable by the guns 58 acting in combination with the sensors 52 and stages
56. Depending upon the particular fasteners to be coated the minimum amount of liquid
coating material 99 sufficient to wick around and cover all of the threads 80 or
less than that amount is shot in totality into the threaded hub 86. By accurate
positioning, metering and selecting the proper pressure of these discrete shots
of liquid material 99 emanating from the guns 58 the material 99 can be substantially
entirely confined within the threaded hub 86 if so desired.
The guns 58 are capable of delivering high speed accurate
metered shots of a wide variety'of liquid coating materials. These materials include,
but are not limited to, fluorocarbons, hydrocarbon and fluorocarbon copolymers,
silicones, waxes, petroleum greases, Teflon® and Teflon®-type materials.
Two materials have been found to be particularly preferred for use in connection
with providing masking, insulating and/or lubricating coatings on fasteners. The
first is a mixture of about 70% by volume DuPont Teflon®-S(#959-101) liquid
and about 30% DuPont T-8748 thinner. The second is a mixture of about 60-70% by
volume Whitford XYLENE® 1661 dry film lubricant manufactured by Whitford Corporation
of Frazer, Pennsylvania and about 30-40% of a solvent mixture that contains about
60% N-methylpyrillidene (NMP) and about 30% Whitford XYLENE®. The guns 58 used
in connection with the present invention preferably utilize a nozzle diameter and
range from about .005" to about .040" and are supplied with coating material under
pressure of about 30lbs/inch2.
It should be appreciated that it is possible to use a single
gun 58 and a single shot of discrete material 99 in connection with the present
invention or any number of additional guns 58 to deliver multiple discrete shots
of material 99 onto fasteners 26. Additionally, as will be described in detail to
follow, the present invention can coat fasteners 26 without the use of any of the
guns 58. The guns 58 can be utilized to place discrete shots of material 99 on surfaces
other than the threads 80 of the fasteners 26. It is preferred that the guns 58
be fully capable of applying at least 20,000 and preferably up to 50,000 discrete
shots of material per hour.
The application station 45 is also provided with one or
more airless spray guns 57. As previously mentioned, demand is increasing for providing
coating material onto portions of multiple surfaces of fasteners at times also having
unusual or non-standard shapes or configurations. One example of this is the fastener
26 with an extended threaded hub 86 as illustrated in Figures 4 and 5. Other examples
include the fasteners illustrated in Figures 7 and 8 respectively. Also, it has
become increasingly desired to cover either all or a very precise portion of non-threaded
areas of fasteners 26 such as lead in areas 82 and/or top surfaces 78 alone or in
addition to the threads 80.
In order to accomplish this purpose, one or more airless
spray guns 57 are used in the present invention, either alone or in combination
with one or more guns 58 as previously described. The airless spray guns 57 are
mounted to the accessory rail 30 by means of stages 55. The stage 55 allows the
gun 57 to be adjusted with respect to its vertical height over the fasteners.26
as well as its horizontal location with respect to the belts 22 and 24. In certain
preferred embodiments, the stage 48 is adjustable in only two axes - vertically
and closer or further from the part. In this case, the corresponding optical sensor
59 is mounted to the block 100 of an adjustable slide 102 as illustrated in Figure
6. The base 106 of the slide is in turn connected to the rail 30. Side to side adjustment
is then accomplished by turning the screw 104 to move the block 100 and stage 55
connected thereto. Alternatively, multiple slides 102 could be stacked together
to provide two or three axis adjustment. The guns 57 use optical sensors 59 as previously
described to sense when a fastener 26 or predetermined portion thereof is present
and then send a signal to trigger operation of the gun 57.
Each gun 57 is provided with an adjustable nozzle 95 as
best illustrated in Figure 3. The spray pattern emanating from the nozzle 95 can
be modified by changing the nozzle 95 to take the form of an annular ring of material
99 such as the area between A and B and A' and B' in Figure 3. Alternatively, the
nozzle 95 can be adjusted vertically to provide a variety of void free spray patterns
such as coverage in the entire area between A and A', C and C' and D and D' for
example. Whether used in connection with one or more guns 58 that fire discrete
shots of liquid coating material 99 or alone the airless spray gun 57 of the present
invention can be utilized to provide a continuous, substantially pin-hole free coating
on all or a portion of the threads 80, the lead-in area 82, the top surface 78 or
any combination of these surfaces. The spray gun 57 operates with the conveyor system
14 continuously moving the fasteners 26 thereby eliminating the need to index the
fasteners and also close off or mask the areas to be coated.
The high pressure and precision of the gun 57 allows precise
delivery of the material onto only the desired preselected surfaces of the fastener
26 and serves to minimize overspray. The material issues from the gun 57 precisely
directed in an airless, high velocity, atomized blast. This blast causes the coating
material to uniformly disperse along the desired fastener surface or swirl previously
applied material around the threads 80 or other surface. The blast is caused by
forcing liquid material in the gun 57 through small slits so as to form a high pressure
vertex that is then forced through a small orifice. The resultant centrifugal force
plus the sudden release of pressure causes the liquid material to atomize into a
precise spray pattern. An optional vacuum system 39 may be located under the gun
57 to assist in urging coating material 99 emanating from the gun 57 into and through
the extended hub 86 or to collect only excess coating material.
Although it should be understood that a variety of different
guns and nozzles can be used in accordance with the present invention and achieve
satisfactory results, a particularly preferred airless spray gun 57 is the Nordson
Airless Spray Gun, Model No. A7A, manufactured by Nordson Corporation of Amherst,
Ohio. A preferred nozzle 95 for use with the gun is manufactured by Deladan Corporation,
Model No. WDA1, with an internal diameter of 0.011" with 45° and/or 70°
of spray angle. The nozzle 95 is preferably attached to the spray gun 57 via an
adaptor. Spray pressure is preferably a minimum of about 500psi. In addition, although
a variety of different stages 55 can be utilized as long as they provide adjustability
in at least two different axes for the guns 57 a particularly preferred commercially
available stage is the model 4574, manufactured by the Daedal Division of the Parker
Corporation of Harrisburg, Pennsylvania.
In the spray pattern illustrated in Figure 3 designated
as C-C', the optical sensor 59 has triggered the nozzle 95 of the spray gun 57 to
spray liquid coating material 99 onto the threads 80 of the fastener 26. This spray
pattern is effective for coating both the lead in area 82 and the threads 80 of
fastener 26. The proper nozzle 95 chosen for this application is a 70° nozzle.
With the 70° nozzle, the liquid coating material 99 will be sprayed perpendicular
to the surface of the threads 80. Part of the atomized liquid material 99 will be
applied to the side of the threads 80 facing the airless supply gun 57. The under
side of the threads 80 opposite to the spray gun 57 will be covered as a result
of the turbulence of the atomized liquid material 99 caused by material contacting
the sharp edge of the thread peak and the high velocity of material discharged.
The excess of the atomized liquid material 99 will then wick to the root of the
threads 80 where through the capillarity of the material it will join together and
build an even pin-hole free film along all portions of the threads 80 of the threaded
As is readily apparent, the spray patterns illustrated
in Figure 3 are exemplary only. The airless spray gun 57 can be utilized alone or
in combination with one or more guns 58 as previously described to coat all or a
portion of the threads 80 of a fastener 26 and/or other surfaces such as the lead
in area 82 and top surface 78. The spray pattern issuing from the gun 57 and bounded
by the lines D and D' is particularly useful for coating deep threaded hubs 86 of
fasteners 26 when used in combination with the discrete shots fired by one or more
guns 58. When used in this manner, the guns 58 deposit discrete shots of liquid
coating material onto the upper threads of the threaded hub 86 while the airless
spray gun 57 is utilized to deposit coating material onto the lower threads of the
threaded hub 86.
Once the appropriate coating of material 99 is deposited
on the fasteners 26 by one or more guns 57, alone or in combination with guns 58,
the belts 22 and 24 of the conveyor system 14 carry the fasteners 26 away from the
application station 46. During this period of time the applied liquid coating material
99 wicks around the threaded hub 86 and covers all of the threads 80 in a substantially
Once the fasteners leave the application station 46, the
device 10 can be optionally provided with an excess material removal station 69.
Due to the precise metering of the guns 58 and 57 at the application station 45
of the present invention, it has been found that an excess material removal station
is generally unnecessary. If still desired, the removal station 69 can take many
An air blow off port 54 can be provided along the conveyor
system 14 to direct pressurized air through the openings of the fasteners 26 to
remove any excess coating material. If excess material has been applied to the fasteners
26, it is likely that as a result of gravity and/or use of the blow off port 54
that it will tend to build up at the bottom 83 of the threads 80 of the fastener
26. If this circumstance is discovered, then it can be easily alleviated using one
or more blotter wheels 60.
These wheels 60 preferably take the form of soft foam wheels
rotating underneath the fasteners 26. The wheels 60 contact and press lightly on
the bottom of the fasteners 26 to remove and carry away any excess coating material.
As the fasteners 26 contact the blotter wheels 60 they are further urged by pressure
wheels 62 that simultaneously contact the top surface 78 of the fasteners 26. The
pressure wheels 62 can optionally be constructed of an absorbent material in order
to remove any excess material from the top surface 78 of the fasteners passing by
the wheels 62.
It is generally preferred that the rotational speed of
the blotter wheels 60 be synchronized with the speed of the belts 22 and 24 carrying
the fasteners so that there is no wiping action on the surface of the fasteners
26. However, in certain applications it may be desirable to move the blotter wheels
60 asynchronously to affect wiping action on the bottom of successive fasteners
26. As the blotter wheels 60 rotate away from the belts 22 and 24, they become partially
submerged in a tank 88 that contains a solvent such as MEK or a mixture of NMP and
XYLENE®, which cleanses the blotter wheels 60 of any excess coating material
between successive presentations of the same section of the blotter wheel 60 to
successive fasteners 26.
Once any excess coating material is removed at the removal
station 69, the conveyor system 14 next transports the fasteners 26 through an optional
drying station 61 as illustrated in Figures 1 and 2. Although generally unnecessary,
this drying station 61 can have one or more air blowers, heaters or combinations
thereof. The heaters can take the form of infrared, radiant or induction heating
elements. Vacuum ducts can also be provided in the drying section to draw solvent
fumes away. The purpose of the drying station 61 is to accomplish sufficient flashing
off of the solvent contained in the coating material 99 on the desired surfaces
of the fasteners 26 to stabilize the coating.
Once the fasteners leave the material fixing station 61
they are next carried toward the end of the conveyor system 14. At that time they
encounter the inverting removal system 16. As will be described in more detail below,
the removal system 16 serves to continuously remove fasteners 26 from the conveyor
system 14, elevate those fasteners 26 and invert them. The removal system 16 features
a magnetic conveyor wheel 34 that is driven by a variable speed motor 40. A continuous
conveyor belt 68 runs between the magnetic wheel 34 and another conveyor wheel 38.
Although a variety of belts can be utilized, a preferred commercially available
belt that has proven effective is the Fluorofab #100-27 Teflon® coated fiberglass
belt (two inches wide by 27 mils thick made by Greenbelt). In operation the speed
of the belt 68 can be adjusted utilizing a variable speed motor 40 so as to efficiently
remove successive fasteners 26 from the conveyor belts 22 and 24 in a spaced uniform
As the fasteners 26 reach the end of the conveyor system
14 their top surfaces 78 adhere to the belt 68 carried by the wheel 34 as a result
of the magnetic attraction between the wheel 34 and the fasteners 26. The rotation
of the wheel 34 causes the fasteners 26 along the belt 68 to be elevated. The elevation
and subsequent inversion of the fastener 26 as they travel on the belt 68 around
the wheel 34 enables clear and easy visual inspection of the bottom of each fastener
26. Inversion of the fasteners 26 also redirects any coating material 99 that may
still be liquid and located near the bottom 83 of the threads 80 to be redistributed
over the entire threaded surface.
Once the fasteners 26 rotate on the belt 68 substantially
180° around the wheel 34, they are completely inverted from their initial positions
on the conveyor system 14 with their top surfaces 78 resting against the top of
the belt 68. The belt 68 then carries the fasteners 26 away from the wheel 34 until
they encounter a removal bar 64 mounted to the inverter frame 42. As illustrated
in Figure 2, the removal bar 64 extends across the belt 68 at a height that permits
contact of the bar 64 with the external surface of the threaded hub 86 of the fasteners
26. In this manner the action of the fasteners 26 hitting the bar 64 is sufficient
to break the frictional engagement between the fasteners 26 and the moving belt
68 and direct them down an incline slide 66.
The end of the slide 66 terminates above a continuous transverse
conveyor belt 94 that runs at a preselected adjustable speed between the conveyor
wheels 74 and 76. A preferred commercially available belt has been found to be an
eight inch wide PVC 120 belt having a friction surface on both sides manufactured
by Hytrol Conveyors, Inc.. The transverse conveyor belt 94 moves the fasteners 26
away from the conveyor system 14. A directing bar 70 is provided along the conveyor
belt 94 near the wheels 76 that is spaced at a vertical distance above the belt
94. This directing bar 70 operates similarly to the previously described removal
bar 64 and contacts the external surface of the threaded hub 86 of the fasteners
26 to break the frictional engagement between the fasteners 26 and the belt 94.
The bar 70 subsequently moves the fasteners onto a ramp
72 that delivers the fasteners 26 in a continuous and even manner into an oven,
other heating device or conveying system therefor. In this manner the inverting
removal system 16 and transverse conveyor system 93 of the present invention serve
to provide a fast and efficient on-line mechanism for removing coated fasteners
from the application conveyor system 14 and into an oven or other heater without
requiring additional material handling of the fasteners.
Alternatively, the bar 70 can be connected to a pneumatic
cylinder or similar device. In this construction the bar 70 oscillates back and
forth across the surface of the belt 94. The oscillation of the bar 70 results in
the fasteners 26 being deposited across the entire width of the ramp 72 over time.
In certain circumstances this has provided improved efficiency in subsequent over
heating of the coated fasteners.
The following examples are given to aid in understanding
the invention. It should be understood that the invention is not limited to the
particular procedures or parameters set forth in those examples.
M14 cage nuts similar to those illustrated in Figure
7 were deposited with their opening centered over the space
between the two belts of a conveyor system of an apparatus as generally illustrated
in Figure 1. The cage nuts were similar to those illustrated in Figure 7 and were
approximately 2 inches long, 1.5 inches wide and 5/16 inch thick. The nuts contained
a protruded shoulder on one surface having a 3/4 inch outer diameter, a chamfered
opening and an off-center hole. The parts were continuously fed by a rotary bowl.
The part were then inverted by means of a specially designed downtrack. The parts
were then deposited onto two spaced parallel steel belts with their protrusions
facing downward. The belts were approximately each 5/8 inch wide and .030 inches
thick. The length of the top track of these conveyor belts was approximately 20
feet. The clearance or space between the belts was about 3/4 inch.
The parts were then moved into the application area by
the conveyor belts. The nuts then encountered two Nordson Zero Cavity guns with
Nordson #276515 modules located on opposite sides of the belts. Each gun applied
a single shot of liquid coating material to opposite sides of the bottom of the
threaded opening. The pot pressure of the liquid material delivered to the fasteners
was about 25psi. The material applied to the nuts was delivered at room temperature
and contained a mixture of about 66% Whitford XYLENE® 1661 high build purple
dry film lubricant and about 33% of a solvent mixutre containing N-methyl-pyrrolidone(NMP)
and XYLENE®. The shots of material were triggered by a pair of Model No. PZ-101
sensors, manufactured by Keyance Corporation, mounted in close proximity to each
of the guns.
The nuts with the coating material applied traveled a short
distance down the conveyor belt and encountered a Nordson Airless Spray Gun Model
No. A7A manufactured by Nordson Corporation of Amherst, Ohio, which deposited a
third shot of material in a round circular pattern that covered the chamfer or lead
in area of the top of the opening and all of the threads of the opening as well.
The material was the same as deposited in the prior two shots. The gun delivering
the third shot was mounted directly overhead the opening of the nuts. The coating
material was delivered at a pressure of less than 500psi. The nuts then traveled
a short distance further down the conveyor system and encountered an air nozzle
directly overhead of the threaded opening. The air issued from the nozzle was at
a low pressure from a 1/4 inch polyurethane tube and served to both assist the spreading
of the material on the desired areas of the nuts and to remove any excess material.
The nuts then encountered a series of absorbent upper and lower blotter wheels whereby
when passing through these wheels any excess material that may have been on the
undesired surfaces of the fastener were removed.
The parts next were removed from the conveyor system by
an elevating and inverting conveyor system. A magnetic pulley was utilized that
attracted the top surface of the parts from the split belt conveying system. Once
the parts were attracted to the magnetic force of the conveyor wheel, the wheel
rotated the parts to a point where their orientation was inverted from the position
they occupied on the split conveyor system. The parts then located above the split
belt conveyor system were moved approximately 2 feet until they encountered a wipe-off
bar which sent the parts down a 1 foot long track that had a drop of approximately
8 inches. At the bottom of the track the parts encountered and moved by a transverse
conveyor system about six feet away from the inverting removal system and the split
belt conveyor system. The parts next encountered a reciprocating wipe-off bar that
oscillated back and forth across the width of the transverse conveyor belt. By this
motion, the parts were directed down a ramp to another transverse conveyor belt
that led them directly into an oven. The parts were then baked and in an oven at
about 350° for approximately 10 minutes. The result was a substantially pin-hole-free
coating of material on the entire threaded surface of the nuts and the chamfer or
lead in area of the protruded shoulder. The parts were coated in a continuous process
at a rate of about 5,000 per hour. Total weight of the coating material applied
was about 150mg. The coating present on the nuts had a uniform appearance and was
free of tears, runs and flaked areas. In addition, the cured coating was effectively
damage resistant to prevent chipping or other coating removal during normal handling
and shipping of the parts.
Internally threaded nuts similar to those illustrated in
Figure 8 were deposited with their openings centered over the space between the
two belts of a conveyor system of an apparatus as generally illustrated in Figure
1. The nuts had a diamond shaped top surface with the distance between the small
points of the diamond being approximately 2 inches and the distance between the
longer opposite points of the diamond being approximately 3 inches in length. The
nuts contained a central threaded aperture that was approximately 3/4 inch deep
and had an outer diameter of approximately 1/2 inch. The top surface of the nuts
had a circular downwardly sloping lead in area between the top surface and the threads.
The parts were hand fed onto the split belt conveying system.
The parts were then processed in exactly the same manner as indicated in Example
I. The specification called for barrier coating material to be deposited on all
of the threads of the fastener and along a precise portion of the rounded circular
lead in portion illustrated in Figure 8.
The process of the present invention was able to coat approximately
3,000 of the parts per hour with coating material and the resulting coating was
precisely placed only on the desired portion of the lead in area and over all of
the threads of the fastener. The coating present on the nuts had a uniform appearance
and was free of tears, runs and flaked areas. In addition, the cured coating was
effectively damage resistant to prevent chipping or other coating removal during
the normal handling and shipping of the parts.
From these examples the benefits of the present invention
can be seen in the high speed application of liquid barrier coating materials to
the threads and/or other surfaces of a continuous stream of fasteners having odd-shapes
or deep threaded hubs and subsequently delivering them directly into an oven or
other heater using an on-line process that does not require any manual handling
in a very precise manner.