U.S. patent number RE34,522 [Application Number 07/675,643] was granted by the patent office on 1994-01-25 for thread lock.
This patent grant is currently assigned to The Oakland Corporation. Invention is credited to Richard B. Wallace.
United States Patent |
RE34,522 |
Wallace |
January 25, 1994 |
Thread lock
Abstract
The method of making a friction locking fastener of the type
having in the thread grooves a first deposit formed of a mixture of
an uncured epoxy resin and a radiation-curable, film-forming
material, and a second deposit of a fluid curing agent and a
radiation-curable, film-forming material. The deposits are made in
the thread grooves at circumferentially spaced locations so that a
very thin coating of the radiation-curable, film-forming material
develops at the surface of each deposit. The deposits are subjected
to high intensity ultraviolet radiation for a few seconds to
transform the coatings developed on the surfaces of the deposits
into thin, continuous, flexible, non-tacky protective films which
cover the still fluid deposits in the thread grooves of the
article. Alternatively, when one or both the resin and the curing
agent are microencapsulated. They may be contained in a single
mixture which includes the radiation-curable material. That
mixture, when deposited and exposed to radiation, will form a
protective film at the surface. The resin will not be polymerized
until the capsule are ruptured.
Inventors: |
Wallace; Richard B. (Bloomfield
Hills, MI) |
Assignee: |
The Oakland Corporation (Troy,
MI)
|
Family
ID: |
22577935 |
Appl.
No.: |
07/675,643 |
Filed: |
March 27, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
160677 |
Feb 26, 1988 |
04847113 |
Jul 11, 1989 |
|
|
Current U.S.
Class: |
427/510; 427/287;
427/388.1; 427/388.2; 427/409; 427/410 |
Current CPC
Class: |
B05D
1/38 (20130101); B05D 3/067 (20130101); B05D
7/54 (20130101); B29C 67/247 (20130101); B05D
7/58 (20130101); B05D 2202/00 (20130101); B05D
2258/02 (20130101) |
Current International
Class: |
B05D
7/00 (20060101); B05D 1/38 (20060101); B05D
3/06 (20060101); B29C 67/24 (20060101); B05D
003/06 () |
Field of
Search: |
;427/54.1,287,388.1,409,388.2,410,510 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Bell; Janyce
Attorney, Agent or Firm: Liniak; Thomas P.
Claims
I claim:
1. The method of making a threaded friction locking article
provided with thread locking means adapted to resist separation
from a mating threaded member which comprises placing at a first
location on the threaded surface of the article a first deposit
.[.comprising.]. .Iadd.consisting essentially of .Iaddend.a fluid
mixture of an uncured resin .[.and.]. .Iadd.having throughout
.Iaddend.a radiation-curable, film-forming material so that a very
thin .Iadd.integral .Iaddend.film coating of said
radiation-curable, first-forming material develops at the surface
of said first deposit, placing at a second location spaced
circumferentially from said first location on said threaded surface
a second deposit .[.comprising.]. .Iadd.consisting essentially of
.Iaddend.a fluid mixture of a curing agent for the resin .[.and.].
.Iadd.having throughout .Iaddend.a radiation-curable, film-forming
material so that a very thin .Iadd.integral .Iaddend.coating of the
radiation-curable, film-forming material develops at the surface of
said second deposit, and thereafter initiating a brief high
intensity radiation of the radiation-curable film-forming material
at the surfaces of said deposits to transform the same into thin,
.Iadd.integral, .Iaddend.continuous, flexible, non-tacky outer
protective films which cover the still fluid mixtures on the
threaded surface of the article, said films being rupturable to
permit intermixing of said resin and curing agent and curing of
said resin.
2. The method as defined in claim 1, which comprises supporting the
article with its axis vertical during deposition of the two
deposits and radiation thereof, in which said deposits when
deposited have a viscosity which permits flow thereof down into the
thread grooves and laterally along the thread grooves while
preventing substantial flow longitudinally of the article.
3. The method as defined in claim 1, wherein said radiation-curable
material in each deposit includes trimethylopropane
triacrylate.
4. The method as defined in claim 1, which comprises applying the
deposit in the thread grooves at a temperature of about 90.degree.
F.
5. The method as defined in claim 1, in which the first deposit
comprises a mixture by weight of about 15%-74% of the resin, about
20%-75% of a monomer, and about 1%-10% of a photoinitiator.
6. The method as defined in claim 1, in which the second deposit
comprises a mixture by weight of about 15%-74% of the curing agent,
about 20%-75% of a monomer, and about 1%-10% of a
photoinitiator.
7. The method of mass producing articles by the method defined in
claim 1, which comprises continuously advancing a series of
articles horizontally through a deposit station and making the
deposits in the thread grooves as the articles advance, and
subjecting the deposits to ultraviolet radiation at a radiation
station beyond the deposit station as the articles continue to
advance.
8. The method of mass producing articles by the method defined in
claim 7, which comprises collecting the finished articles at random
immediately after exposure to the ultraviolet radiation.
9. The method defined in claim 8, in which said first deposit
comprises a mixture by weight of about 15%-74% of epoxy resin,
about 20%-75% of a trimethylopropane triacrylate, and about 1%-10%
of a photoinitiator.
10. The method as defined in claim 8, in which said second deposit
comprises a mixture by weight of about 15%-74% of an amine curing
agent, about 20%-75% of trimethylopropane triacrylate, and about
1%-10% of a photoinitiator.
11. The method of producing a threaded article provided with thread
locking means adapted to resist separation from a mating threaded
article which comprises depositing a fluid lock-forming material on
the threaded surface of the article to be received in the thread
grooves and fill the bottoms of the thread grooves, the fluid
material .[.comprising.]. .Iadd.consisting essentially of
.Iaddend.a fluid mixture including uncured resin contained in
micro-capsules .[.,.]. .Iadd.and .Iaddend.a curing agent for the
resin.[., and.]. .Iadd.having throughout .Iaddend.a
radiation-curable film-forming material, and thereafter subjecting
the radiation-curable material at the surface of said deposit to
radiation to transform the same into .[.a.]. .Iadd.an integral,
.Iaddend.thin, continuous, flexible, non-tacky outer protective
film which covers the still fluid mixture in the thread grooves of
the article, said film and micro-capsules being rupturable to
permit intermixing of said resin and curing agent and curing of
said resin.
12. The method as defined in claim 11, wherein the
radiation-curable material includes trimethylopropane
triacrylate.
13. The method as defined in claim 11, wherein said
radiation-curable material comprises a monomer and a
photoinitiator.
14. The method as defined in claim 13, in which the monomer is
trimethylopropane triacrylate.
15. The method as defined in claim 1, in which the
radiation-curable material includes a monomer and a photoinitiator,
the monomer is trimethylopropane triacrylate, and the
radiation-curable material is subjected to ultraviolet
radiation.
16. The method of producing a threaded article provided with thread
locking means adapted to resist separation from a mating threaded
article which comprises depositing a fluid lock-forming material on
the threaded surface of the article to be received in the thread
grooves and fill the bottoms of the thread grooves, the fluid
material .[.comprising.]. .Iadd.consisting essentially of
.Iaddend.a fluid mixture of an uncured resin and a fluid curing
agent for said resin, one of which is contained in micro-capsules,
said mixture .[.also including.]. .Iadd.having throughout
.Iaddend.a radiation-curable film-forming material, and thereafter
subjecting the radiation-curable material at the surface of said
deposit to radiation to transform the same into .[.a.]. .Iadd.an
integral, .Iaddend.thin, continuous, flexible, non-tacky outer
protective film which covers the still fluid mixture in the thread
grooves of the article, said film and micro-capsules being
rupturable to permit intermixing of said resin and curing agent and
curing of said resin.
17. The method as defined in claim 1 in which the radiation curable
material comprises a monomer and a photoinitiator.
Description
This invention relates generally to a threaded member having a
thread locking material applied to the threads to oppose separation
when engaged with another threaded member, and refers more
particularly to a method of providing a protective coating over the
thread locking material prior to engagement.
BACKGROUND AND SUMMARY OF THE INVENTION
Self-locking threaded fasteners have in the past been made by means
of a two-part adhesive, such as an uncured epoxy resin and a
polymerizing agent. Deposits of the uncured resin and curing agent
are applied to the threads of the fastener. The deposits become
mixed when the fastener is engaged with a mating member, effecting
a cure of the resin to provide, a thread lock. The resin has also
been micro-encapsulated and the microcapsules mixed with the
polymerizing agent to provide a slurry which is applied to the
threads. U.S. Pat. No. 3,746,068 discusses micro-encapsulation.
Protection films over the deposits protect them until the time when
the fastener is actually engaged with a mating threaded member.
Each deposit may be coated with polyvinyl alcohol in a water
solution to form the protective film. My prior U.S. Pat. Nos.
4,059,136 and 4,081,012 are of interest in this regard. My prior
U.S. Pat. No. 4,325,985 discloses an improvement in which the
deposits are coated with ultraviolet curable, protective films.
Other patents of interest are U.S. Pat. Nos. 3,489,599, 3,746,068
and 3,814,156.
The present invention is a further improvement in which ultraviolet
curable material, rather than being applied as a subsequent
coating, is mixed with the resin and curing agent prior to the
deposit thereof on the threads of the fastener. That portion of the
ultraviolet curable material which is near the surface of the
deposits is then cured by ultraviolet light to form a protective
skin or film.
These and other objects of the invention will become more apparent
as the following description proceeds, especially when considered
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of a twin belt conveyor which is
part of apparatus that may be used in the practice of the method of
this invention.
FIG. 2 is a sectional view on the line 2--2 in FIG. 1.
FIG. 3 is a diagrammatic plan view of apparatus that may be used in
the practice of the method, including the conveyor shown in FIG. 1.
The apparatus illustrated is only one example of apparatus that may
be used in the practice of the invention.
FIG. 4 is an enlarged fragmentary view of a portion of a bolt
showing the deposited material and the protective films
thereover.
DETAILED DESCRIPTION
Reference is made to the drawing as illustrative of a procedure in
accordance with the invention, where the uncured resin and the
curing agent remain fluid and are protected by protective films
until used.
A series of threaded fasteners or bolts 10 are supplied to the
conveyor 5. Conveyor 5 comprises a pair of horizontal, laterally
spaced, parallel belts 12 between which the bolts are suspended by
their heads. The conveyor belts are moved by means (not shown) in
the direction of the arrow. The individual bolts are supplied to
the conveyor at a loading station A. At this loading station, the
bolts are at ambient temperature, which may be assumed to be about
70.degree. F. In practice, the bolts may be supported with their
heads in contact with another, although they are shown spaced
apart.
Preferably, the temperature of the bolts is raised between stations
A and B to about 90.degree. F. This may be accomplished by heaters
indicated at 18.
At station B, applicators 14 and 16 on opposite sides of the belt
conveyor deposit controlled amounts of fluid material onto opposite
sides of the threaded portions of the bolts, The fluid deposits 15
applied to one side of the bolts by the applicator 14 is a mixture
of uncured resin, in this instance epoxy resin, and a film-forming
ultraviolet curable material. The fluid deposits 17 applied to the
opposite sides of the bolts by the applicator 16 is a mixture of a
curing agent or hardener for the resin, in this instance tertiary
amine, and the same film-forming ultraviolet curable material.
Applicators 14 and 16 may be of any suitable known type, and may,
for example, be of the type disclosed in the prior above identified
patents. The fluid deposits have a viscosity such that they flow
down into the thread grooves and laterally along the thread
grooves, remaining essentially at the axially located zones of
deposition, which may extend for several threads along the bolt.
That portion of the ultraviolet curable material in each deposit
which is near or at the surface of the deposit forms a very thin
continuous coating.
Heat is again applied after the bolts move beyond applicators 14
and 16, by heaters 19.
The preheat of the bolts by heaters 18 and the post heat by heaters
19 warms the bolts and the deposits and assists in the desired flow
of the deposits into the thread grooves. This "lay down" of the
deposits also improves the appearance of the coated bolt. Heaters
18 and 19 are optional and are used only when necessary to achieve
the desired flow and "lay down". When the method is carried out in
a warm environment, as in summer time. both preheat and post heat
may not be needed and can be omitted.
The fasteners continue their movement on the conveyor past station
C where there are ultraviolet cabinets 22 and 24 on opposite sides
of the conveyor. The rate of advance of the bolts is such that the
deposits on opposite sides of the bolts are exposed to high
intensity radiation at station C for only a very few seconds as,
for example, less than 10 seconds, and preferably between 2 and 5
seconds
The source of radiation may be elongated ultraviolet radiating
tubes, backed by reflectors, and positioned on both sides of the
conveyor beneath the conveyor belts and rated at 200 watts per
inch.
The effect of the ultraviolet radiation at station C is to convert
the ultraviolet curable material at the surface of the deposits 15
and 17 to a fully cured and set film or skin 26.
The films or skins formed over the deposits 15 and 17 by this
process are extremely thin, flexible, dry, non-tacky and
continuous, lacking any pin holes associated with prior covering
methods.
The bolts then pass a final cooling station provided by blowers 40
to reduce or remove any heat build-up that may have resulted from
exposure to the ultraviolet lights and to better prepare the bolts
for deposit in bulk shipping containers 42 at the end of the
conveyor immediately after the radiation treatment. Cooling air
raises the viscosity of the deposits which gives support to and
strengthens the skins so that the deposits remain intact when the
bolts are discharged into the containers 42 and the bolts do not
stick together.
In general, the ultraviolet curable material mixed with the resin
of deposit 15 and with the curing agent of deposit 17 is made up
from one or more monomers and a photoinitiator. Such ultraviolet
curable material is activated to form a skin on the deposits by a
photochemical reaction.
Typical monomers that may be used include chemical compounds which
are classified as acrylic esters, methacrylic esters, vinyl esters,
vinyl ethers, acrylic ethers, allyl esters, allyl ethers, epoxides,
styrene and substituted acrylamides, acrylonitrile, and dienes. A
particularly good monomer for the purposes of this invention is
trimethylopropane triacrylate (TMPTA).
The photoinitiators can include ketones, benzophenones, aromatic
ketones. Michler's ketones, benzoin ethers, alkyl aryl ketones,
benzil ketals, oxime esters, halogenated thioxanthones, Onium
salts, fluoborates, peroxides, azo free radical generators, and
promoters like tertiary amine accelerators, organometallic
complexes and mixtures of the above.
The locking resin chosen for the deposits 15 must be of a nature
when cured to adhesively resist separation of two threadedly
engaged members. As stated, epoxy is a particularly good resin for
this purposes, a suitable example being bis-phenol A resins which
are commercially available.
The curing agent selected for the deposit 17 should be one which
readily effects a cure of the resin in deposit 15 when the two are
mixed. A tertiary amine has been found to be an effective curing
agent for an epoxy resin.
Ultraviolet radiation is preferred because of convenience, ready
availability, and economy, and also because it accomplishes its
purpose effectively and very quickly. However, other types of
radiation may be employed, such, for example, as electron beam
radiation.
As mentioned above, TMPTA has been found to be an outstanding
monomer. It will not react with the resin or with the curing agent
when mixed with them. However, when the deposits 15 and 17 are
mixed together to cure the epoxy, as when two fasteners are
threaded together, the TMPTA does correct with the epoxy, so that
that portion below the surface which does not cure in the
ultraviolet light will compliment the end result. This has been
proven to be true under torque tests of two threadedly engaged
fasteners at temperatures as high as 400.degree. F.
The deposits 15 and 17 of locking resin plug ultraviolet curable
material and of hardener or curing agent plus ultraviolet curable
material preferably have compositions by weight in the following
ranges:
______________________________________ Resin Deposit 15 Hardener
Deposit 17 ______________________________________ 15%-74% locking
resin (A) 15%-74% hardener (D) 20%-75% monomer (B) 20%-75% monomer
(B) 1%-10% photoinitiator (C) 1%-10% photoinitiator (C)
______________________________________
______________________________________ Hardener Deposit 17 Example
1 100 ml tertiary amine (D) 75 ml acrylate monomer (B) 3 ml
aromatic hydroxy ketone (C) Resin Deposit 15 100 ml epoxy resin (A)
35 ml acrylate monomer (B) 1.4 ml aromatic hydroxy ketone (C)
Hardener Deposit 17 Example 2 100 ml tertiary amine (D) 75 ml TMPTA
(B) 3 g thioxanthone (C) Resin Deposit 15 400 ml epoxy resin (A)
140 ml TMPTA (B) 9.8 g. Michler's ketone (C)
______________________________________
In the foregoing examples, the capital letters in parentheses
following each component represents the appropriate category as
described in the material immediately proceding the examples.
The method of this invention has a number of advantages over prior
methods, in particular the method involving the use of a
subsequently applied water base cover coat or skin. Among the
advantages are:
(a) It is possible to substantially reduce the overall length of
the conveyor apparatus used to practice the invention and to
increase the speed of the conveyor, thereby substantially reducing
production time.
(b) The need for blowers and dryers, etc. to drive off the aqueous
or organic solvent in a cover coat is eliminated, reducing overall
power consumption.
(c) Pin holes and imperfections in the cover coat for the deposits
are no longer a problem since the generation of a skin by
ultraviolet light is uniform and total. Pin holes are simply not
acceptable. They permit escape of the deposits and can cause skin
problems for anyone handling the parts.
(d) A cover or skin cured by ultraviolet light according to the
present invention makes the deposits water and solvent proof in
contrast to some other types of self-locking deposits.
(c) Since the ultraviolet curable material is mixed with the
deposits rather than subsequently applied, such material covers
only the deposits themselves and does not get into the spaces
between the deposits where it might interfere with a successful
mixing of the deposits when the fasteners are engaged.
This method lends itself readily to mass production of friction
locking fasteners which may be collected at random at the end of
the conveyor line immediately after being exposed to radiation. The
film or skin formed on the deposits is then, dry, flexible and
non-tacky so that the randomly collected fasteners do not stick
together and the locking resin and hardener are covered and well
protected against displacement or loss. When one of these fasteners
is engaged with a mating threaded member, the two deposits are
mixed together, effecting a cure of the resin to provide a thread
lock.
In the foregoing, a mass production method has been described in
which the uncured fluid resin and fluid actuator or hardener are
deposited on a threaded zone in side-by-side relation, each deposit
including an ultraviolet curable material which when subjected to
ultraviolet light forms a protective film over the deposits.
However, the invention is also applicable to mass production of
threaded articles in which the resin and/or hardener may be
micro-encapsulated.
It has been suggested that thread locks may be formed by suitably
supporting a liquid or fluid locking material in microscopic,
pressure rupturable capsules located in the thread grooves of a
threaded article.
In accordance with my own prior U.S. Pat. No. 4,325,985, one or
both of the resin and hardener are micro-encapsulated and deposited
in a threaded zone, the deposit subsequently being spray coated
with an ultraviolet curable material which is exposed to radiation
to form a protective film. Some of the capsules rupture when the
article is threaded into a mating threaded article to effect
polymerization.
In accordance with the present invention, the material to be
deposited may contain a mixture of micro-encapsulated uncured fluid
resin in a suitable fluid hardener or polymerizing agent for the
resin, and an ultraviolet curable material. The hardener, instead
of the resin, may also, if desired, be microencapsulated, or both
may be micro-encapsulated.
The resin, hardener, and ultraviolet curable material may be of the
same material as heretofore described.
In accordance with the invention, this mixture of resin and
hardener, at least one of which is micro-encapsulated, and
including the ultraviolet curable material, may be serially applied
to the articles as they pass an applicator station. This may be the
station B in FIG. 3, where the mixture may be applied at one side
of the articles 10, or at both sides. In the latter case, the fluid
mixture may flow around the thread grooves to form a 360.degree.
ring. Fluidity and viscosity are preferably such as to prevent
substantially flow axially across the thread grooves.
Substantially immediately after application of the fluid mixture,
the mixture is exposed to a very brief radiation treatment by
ultraviolet lamps. This may be at station C in FIG. 3, where
ultraviolet sensitive material at the surface of the deposits is
set into an extremely thin, flexible, dry, non-tacky, protective
cover film. The films cover the deposits, so that the articles do
not stick together. The time of exposure to ultraviolet light is
the same as that described in the previous embodiment. Protected by
the film is the mixture containing the resin and the hardener.
Since the resin or hardener or both have been micro-encapsulated,
the resin and hardener are separated from one another to prevent
premature mixing and polymerization of the resin.
In U.S. Pat. No. 3,746,068 there is suggested microencapsulation of
an unpolymerized resin in a fluid binder to produce a mixture
suitable for application to the threads of a threaded article. The
binder includes fluids or liquids such as toluene, all capable of
being eliminated by evaporation, thus requiring a protracted drying
period in the absence of a protective film.
In accordance with the present invention, the fluid deposit is
protected by a film which is formed substantially immediately
following application of the deposit, so that no protracted drying
period is necessary. No binder is necessary nor is one present in
the mixture. Even if both the resin and hardener are
micro-encapsulated, the radiation curable material serves the
purpose of holding the mixture together in a fluid slurry until the
protective film is formed.
Prior U.S. Pat. No. 3,814,156 discloses a mixture of separately
micro-encapsulated two part adhesives in a fluid binder, again
requiring a protracted drying period. before the threaded articles
can be randomly accumulated without sticking.
For a more complete description of the capsules, reference is again
made to my own prior U.S. Pat. No. 4,325,985 as well as the other
patents disclosed herein.
When a fastener having a deposit as herein described, in which one
or both the resin and hardener have been microencapsulated, is
engaged in a mating threaded member, the microcapsules rupture so
that the resin and hardener mix together, curing the resin to a
solid state and producing a thread lock. The protective film over
the deposit breaks up and "balls" up and assists in rupturing the
capsules.
* * * * *