U.S. patent application number 11/412570 was filed with the patent office on 2007-02-22 for apparatus and methods for in-line cleaning of contaminant-coated hangers.
Invention is credited to Michael D. Blackburn, Edgar L. Dean.
Application Number | 20070039632 11/412570 |
Document ID | / |
Family ID | 37766366 |
Filed Date | 2007-02-22 |
United States Patent
Application |
20070039632 |
Kind Code |
A1 |
Dean; Edgar L. ; et
al. |
February 22, 2007 |
Apparatus and methods for in-line cleaning of contaminant-coated
hangers
Abstract
Devices and methods for continuous cleaning of
contaminant-coated hangers or racks by removing the overspray
contaminant that is detrimental to the powder coating operation.
Exemplary cleaning systems use radio frequency (RF) energy to heat
the overspray coating and soften it. The coating is heated to an
intermediate level that is less than the incineration point,
wherein the coating would be reduced to ash.
Inventors: |
Dean; Edgar L.; (Houston,
TX) ; Blackburn; Michael D.; (New Waverly,
TX) |
Correspondence
Address: |
SHAWN HUNTER
P.O Box 270110
HOUSTON
TX
77277-0110
US
|
Family ID: |
37766366 |
Appl. No.: |
11/412570 |
Filed: |
April 27, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60709576 |
Aug 19, 2005 |
|
|
|
Current U.S.
Class: |
134/19 ; 118/308;
118/500; 134/38 |
Current CPC
Class: |
B08B 1/02 20130101; B08B
7/0071 20130101; B08B 1/04 20130101; F23G 2201/50 20130101 |
Class at
Publication: |
134/019 ;
134/038; 118/500; 118/308 |
International
Class: |
F23J 1/00 20060101
F23J001/00 |
Claims
1. An apparatus for removing powder coating residue from an object
comprising: a heater to heat powder coating residue coating the
object to a temperature sufficient to soften the residue but not
sufficient to incinerate the residue; and a residue cleaner for
removing softened residue from the object.
2. The apparatus of claim 1 wherein the heater heats the object
such that an outer portion of the object is heated to a temperature
within the range from about 500.degree. F. to about 750.degree.
F.
3. The apparatus of claim 1 further comprising an in-line conveyor
system to convey articles past the heater and the residue cleaner,
the conveyor system comprising: a moveable chain carried on a rail;
and a hanger retained upon the chain for removably supporting
articles to be powder coated.
4. The apparatus of claim 1 wherein the residue cleaner comprises a
brush.
5. The apparatus of claim 1 wherein the object to be cleaned
comprises a hanger.
6. The apparatus of claim 1 wherein the heater comprises an
induction coil unit.
7. A system for removing coating material from hangers suspended
from an in-line conveyor system used to move articles through a
zone for applying coating to the articles, the system comprising: a
hanger heater for heating a hanger to a temperature sufficient to
heat coating material on the object to a temperature sufficient to
soften the coating but not sufficient to incinerate the coating;
and a residue cleaner for physically removing heated coating
material from the hanger.
8. The system of claim 7 wherein the hanger heater comprises an
induction heating coil adapted to heat the hanger to a temperature
such that an outer surface of the hanger reaches a temperature in
the range from about 500.degree. F. to about 750.degree. F. to
soften coating accumulated on the hanger but not incinerate it to
ash.
9. The system of claim 7 wherein the residue cleaner comprises: a
rotatable wire brush head; and a rotary motor for rotating the
brush head.
10. The system of claim 7 further comprising a hanger guide to
orient the hanger to pass within a predetermined distance of the
hanger heater.
11. The system of claim 10 wherein the hanger guide comprises a
moving friction belt.
12. The system of claim 10 wherein the predetermined distance is
from about 1/8 inch to about 3/8 inch.
13. A method for removing coating material from hangers suspended
from an in-line conveyor system used to move articles through a
zone for applying coating to the articles, the method comprising
the steps of: heating a hanger to a temperature such that the outer
surface of the hangers reaches a temperature in the range from
about 500.degree. F. to about 750.degree. F. to soften coating
accumulated on the hanger but not incinerate it to ash; and
removing the coating accumulated on the hanger.
14. The method of claim 13 wherein the step of heating the hanger
further comprises heating the hanger until the outer 5-10
thousandths of an inch of the surface of the hanger reaches a
temperature in the range from about 500.degree. F. to about
750.degree. F.
15. The method of claim 13 wherein the step of heating the hanger
further comprises moving the hanger to a predetermined distance
from a hanger heater that is in a range from about 1/4 inch to
about 1 inch.
16. The method of claim 15 wherein the hanger is moved to the
predetermined distance for a predetermined period of time that is
from about 4 to about 8 seconds.
17. The method of claim 16 wherein the step of heating the hanger
further comprises contacting the hanger with a hanger guide to move
the hanger to the predetermined distance for the predetermined
period of time.
Description
[0001] This application claims the priority of U.S. provisional
patent application Ser. No. 60/709,576 filed Aug. 19, 2005.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to systems and methods for
removal of overspray residue, or other residue, from hangers used
in in-line powder coating conveyor systems. In other aspects, the
invention relates to the cleaning of component support racks.
[0004] 2. Description of the Related Art
[0005] Powder coating is a process of coating an article, such as
an automotive part or other metallic object, with a powdered paint
coating and then curing the coating with heat to provide a
desirable finish. Powdered paint is blown toward the article as a
spray under pneumatic pressure. Electrostatic charge is used to
cause the powdered paint particles to adhere to the article. A
popular method of powder coating a large number of articles is an
in-line conveyor-type powder coating system wherein hooks or
hangers support the articles to be powder coated on a moving
conveyor system. The articles move through spraying and curing
stations to provide the desired finish upon the articles.
Electrostatic charge is transmitted through the hangers to the
article being supported and conveyed through the system.
[0006] Effective powder coating requires that the support hanger be
relatively free from overspray residue where electrical or ground
contact is made between the support hanger and the part to be
coated. Overspray residue build-up on the support hanger will
significantly reduce the grounding needed to make the electrostatic
attraction of the powder particles to the article effective. If the
overspray residue is not removed, significant problems develop in
the powder coating process. The powder is not sufficiently
attracted to the article, and this may result in uneven coatings or
high consumption of powder used to coat the articles. In some
instances, improperly coated parts are scrapped because it is not
economical to remove the coating from them and recoat them.
[0007] To solve the problem of coating overspray, the hangers are
typically removed from the conveyor line after a certain number of
spray runs and then are placed in a burn-off oven to remove the
overspray coating. However, this solution has significant
drawbacks. Removing the hangers is time consuming and requires a
significant number of replacement hangers. In addition, the cost of
operating the burn-off oven is significant.
[0008] Attempts have been made to develop "in-line" hanger cleaning
systems wherein support hangers are cleaned of overspray without
the necessity of removing them from the conveyor line. One such
system is described in U.S. Pat. No. 6,520,097 issued to Shiveley.
Shiveley describes an in-line conveyor-type powder coating system
wherein hangers are cleaned by passing them through an in-line
hanger heating station that heats the hangers with a high-intensity
energy source to quickly bring the coating on the hangers to the
coating incineration point. U.S. Pat. No. 5,617,800 issued to
Moreschi et al. describes a similar system wherein the hangers are
heated to a temperature sufficient to thermally decompose the paint
particles to ash and gaseous combustion products. U.S. Pat. No.
3,830,196 issued to Guttman et al. also describes a similar in-line
cleaning system in which hangers are passed through a heating oven
to cause accumulated paint to be reduced to ash. The ash is then
washed off by rinsing. In each of these in-line hanger cleaning
systems, high energy thermal sources are used to heat the hangers
to the point where the coating is incinerated to ash.
Unfortunately, incinerating the coating overspray to the point
where it is reduced to ash creates significant fumes, and it is
necessary to provide elaborate venting for such fumes. The creation
of these fumes causes safety concerns. The burn-off oven tempers
(softens) the hook and reduces its load carrying capacity. Also,
the expense associated with heating the hangers to a degree to
cause the coating to be incinerated is significant.
[0009] The problems associated with overspray on hangers extend as
well to metal racks that are used to hold smaller components during
the powder coating process. These metallic racks are typically hung
from the hangers of the conveyor and must remain substantially free
of coating residue in order to be properly grounded. Unfortunately,
there is no effective technique for cleaning these racks other than
use of a standard burn-off oven, which, as noted previously, is
significantly costly in terms of fuel and labor costs.
[0010] The present invention is directed to overcoming the problems
of the prior art.
SUMMARY OF THE INVENTION
[0011] The present invention provides improved devices and methods
for continuous cleaning or contaminant-coated hangers or racks by
removing the overspray contaminant that is detrimental to the
powder coating operation. In a preferred embodiment described
herein, an in-line cleaning system uses induction heating via radio
frequency (RF) energy to induce eddy currents in the hanger to heat
the overspray coating and soften it. The coating is heated to an
intermediate level that is less than the incineration point,
wherein the coating would be reduced to ash. Other heating sources
will work, but are not preferred as they entail a greater cost.
[0012] In a currently preferred embodiment, hanger guides are used
to physically guide the hangers through the induction coils so that
they remain substantially at a predetermined distance from the coil
surface during conveyance. After the coating is softened by the
heating, abrasive brushes or other tools are used to remove the
softened coating.
[0013] An alternative embodiment of the invention is also described
wherein components-carrying racks can be cleaned of overspray using
a conveyor system.
[0014] The systems and methods of the present invention provide a
number of advantages over conventional systems for cleaning support
hangers. The in-line cleaning system of the present invention
utilizes a reduced heating temperature for cleaning of the hangers.
This results in significant savings in energy and cost. Also, the
reduced heating temperature eliminates the concern of fumes created
by the incineration process and does not detrimentally affect the
metallurgy of the hanger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] For detailed understanding of the invention, reference is
made to the following detailed description of the preferred
embodiments, taken in conjunction with the accompanying drawings in
which reference characters designate like or similar elements
throughout the several figures of the drawings.
[0016] FIG. 1 is a schematic illustration of an in-line
conveyor-type powder coating arrangement that incorporates an
exemplary hanger cleaning system constructed in accordance with the
present invention.
[0017] FIG. 2 is a side view showing components of the hanger
cleaning system in greater detail.
[0018] FIG. 3 is an isometric perspective view of portions of the
hanger cleaning system shown in FIG. 2.
[0019] FIG. 4 is an illustration of an exemplary hanger heating
element used in the hanger heating system shown in FIGS. 2 and
3.
[0020] FIG. 5 is an illustration of an alternative exemplary hanger
heating element used in the hanger heating system shown in FIGS. 2
and 3.
[0021] FIG. 6 is an illustration of an alternative embodiment of
the present invention for cleaning disassembled rack components
associated with an in-line powder coating process.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] FIG. 1 depicts an exemplary in-line conveyor-type powder
coating system 10 having an in-line moving conveyor 12 with belt or
chain (not shown) that moves along a monorail 14 under the impetus
of a prime mover (not shown), as is known in the art. Carriers 16
are suspended from the chain and carry removable hangers 18, of a
type known in the art for supporting articles 19 to be coated with
paint. Although the monorail 14 is depicted in FIG. 1 as being in a
straight linear arrangement, it may in fact be arranged in a
circular, oval, or other closed shape so that the carriers 16 are
moved along a continuous track.
[0023] The coating process equipment of the powder coating system
10 includes a powder spray station 20 and a curing station 22, both
of the variety known in the art for powder coating operations. As
the structure and operation of these components are well known,
they will not be described in any detail herein.
[0024] In addition to the coating process equipment, the powder
coating system 10 includes a hanger cleaning system 24 in
accordance with the present invention. The structure and function
of the hanger cleaning system will be described in greater detail
shortly. In operation, movement of the hangers 18 and articles 19
is in the direction of arrow 26 in FIG. 1. The hangers 18 and
articles 18 move first through the powder spray station 20, where
they are sprayed with powdered paint, which is electrostatically
attracted to the articles 19 and hangers 18 via grounding of the
hangers 18 through the monorail 14. Upon exiting the spray station
20, the hangers 18 now are coated, at least partially with
overspray. Next, the articles 19 and hangers 18 are moved through
the curing station 22 wherein the paint coating is cured onto both
the articles 19 and hangers 18. Articles 19 are then removed from
the hangers 18. The hangers 18 continue through the hanger cleaning
system 24 wherein they are cleaned of the accumulated overspray.
The hangers 18 are now available to be reused by the powder coating
system 10.
[0025] In a currently preferred embodiment, the hanger cleaning
system 24 includes a hanger heater 26 and a residue cleaner 28. The
hanger heater 26 preferably includes two shoes 30, 32 of a split
induction coil, as depicted in FIGS. 3 and 4. During operation, the
shoes 30, 32 are disposed on either side of the hanger 18 being
heated. In an alternative embodiment, illustrated in FIG. 5, the
hanger heater 26 comprises a single induction heating coil source
34. Electrical lines 36 extend from the hanger heating sources to a
power source 38 that is used to energize the hanger heater 26. The
hanger heater 26 is capable of heating the hangers 18 to a point
wherein the outer 5-10 thousandths of an inch of the surface of the
hangers 18 reaches a temperature in the currently preferred range
from about 500.degree. F. to about 750.degree. F. This range of
temperatures is sufficient to break the bond of the coating, or
delaminate the coating, from the base metal surface of the hanger
18. However, it is not high enough to incinerate the coating and
reduce it to ash. For optimal heating, the hangers 18 should pass
from about 1/8'' to about 3/8'' away from the heating source 34 or
heating sources 30, 32 during operation of the system 10.
Preferably, each hanger 18 should pass adjacent the heating sources
30, 32 or heating source 34 for a period of time of about 4-8
seconds, although the specific length of time will vary somewhat
depending upon the speed of the conveyor 12 and the size of the
power source. To help accomplish this, it is currently preferred
that the hanger cleaning system 24 incorporate a hanger alignment
guide system 50, as will be described. Suitable inductive coils for
use as hanger heater 26 are available commercially from, for
example, Inductoheat, Inc. of Madison Heights, Mich. The hanger
heater 26 is preferably cooled by water pumped from a cooling heat
exchanger (not shown).
[0026] The residue cleaner 28 preferably comprises a pair of
rotatable wire brush heads 40 that are each rotated by a rotary
motor 42 (one shown in FIG. 2). The brush heads 40 are located so
that they will contact the outer surface of each of the hangers 18
as they pass adjacent the brush heads 40, as FIG. 3 illustrates. In
an alternative embodiment, the residue cleaner 28 can comprise one
or more stationary brushes that will contact the hangers 18 to help
remove the delaminated coating. It is preferred that a residue
collection bin 44 be located below the brush heads 40 to collect
those deposits that are scraped away from the hangers 18 by the
brush heads 40.
[0027] A vacuum system 46 with vacuum heads 48 may be located
proximate the residue cleaner 28 to evacuate the residue removed
from the hangers 18 by the residue cleaner 28. The vacuum system 28
contains an appropriate cyclone separator and filters (not shown)
of a type known in the art to remove the fumes. A suitable vacuum
system for this application would be available commercially from,
for example, Donaldson Torit, 100 North Central Expressway, Suite
800, Richardson, Tex. 75080.
[0028] Hanger guide 50 is made up of a pair of moving friction
belts 52 that will contact the lateral sides of the hangers 18 and
physically move them past the induction coil hanger heater 26. The
hanger guide 50 centralizes and orients the hangers 18 so that they
pass within a predetermined proximate distance of the hanger heater
26. In a currently preferred embodiment, the hanger guide 50
locates the hangers 18 from about 1/8 inch to about 3/8 inch from
the heating sources 30, 32, or 34 for optimal effect. A frame 54
(FIG. 2) is secured to the monorail 14 and serves to support and
partially enclose many of the components of the hanger cleaning
system 24.
[0029] FIG. 6 depicts an alternative embodiment of the present
invention wherein a cleaning system 100 is used to clean the
components 102 of a rack that is used to retain smaller components
that are being coated with paint. The exemplary cleaning system 100
shown in FIG. 6 includes a first conveyor 104 onto which rack
components 102 to be cleaned are placed. It will be understood by
those of skill in the art that the components 102 are portions of
typically rectangular metallic support racks of a type known in the
art which may be readily disassembled into component parts for
cleaning. The components 102 will pass from the first conveyor 104
to a second conveyor 106 through an escapement or gate 108 that
will help to orient the components 102 and regulate their entry
onto the second conveyor 106 (i.e., the components 102 are passed
onto the second conveyor 106 one at a time). The second conveyor
106 includes a component guide 109 with a converging throat that
leads to component heater 110. The component heater 110 is an
induction coil-style heater of the same type as described
previously for use with the hanger cleaning system 24 described
earlier. The component heater 110 is powered by a suitable power
supply 112. Rotary abrasive brushes 114 are located downstream of
the component heater 110. A collection bin 116 is positioned at the
end of the second conveyor 106 for collection of the cleaned
components 102.
[0030] In operation, coating-contaminated components 102 are loaded
onto the first conveyor 104 and pass through the gate 108 to the
second conveyor 106. The second conveyor 106 conveys the components
102 through the guide 109 and the component heater 110 whereupon
the components 102 are heated to a point that is less than the
incineration point wherein the coating would be reduced to ash. The
heated components 102 then are conveyed through the abrasive
brushes 114, wherein they are cleaned of the heated coating.
[0031] Those of skill in the art will recognize that numerous
modifications and changes may be made to the exemplary designs and
embodiments described herein and that the invention is limited only
by the claims that follow and any equivalents thereof.
* * * * *