Paint bake oven

An improved paint bake oven (10) of a modular construction is disclosed as including a convection heating module (12), exhaust modules (64), and a radiant drying module (80). The heating module (12) includes outer and inner housings (14) and (16) as well as an upper central supply plenum (20) and a central upper return plenum (28) that cooperate to provide efficient gas flow to painted products being baked upon passage through the heating module. Each exhaust module (64) is connected to an associated heating module so as to receive and exhaust gas therefrom to the environment. The radiant drying module (80) is located upstream from the heating module (12) and includes an outer insulated housing (84), an inner housing (86) having side passages (92) located on opposite sides of a product passage of the drying module (80), and a heater (96) that supplied heated gas to the side passages (92) to provide radiant heating that initially dries the painted products.

TECHNICAL FIELD 
This invention relates to a paint bake oven of the type conventionally used 
to bake products after painting in order to provide a hard and durable 
painted coating on the products. 
BACKGROUND ART 
One type of paint bake oven which is conventionally used to bake painted 
vehicle bodies includes an elongated housing of a rectangular 
cross-section to which heated gas is supplied to provide baking of painted 
vehicle bodies upon conveyance through the housing. This type of oven 
conventionally includes a pair of gas supply ducts respectively extending 
along the upper lateral corners of the housing and having outlets for 
directing the heated gas downwardly against the floor of the housing to 
provide gas deflection back up toward the conveyed vehicle bodies. A 
damper conventionally extends between the pair of supply ducts and is 
adjustable to control the flow of gas upwardly to an outlet duct through 
which the gas is returned to a heater prior to flow back to the supply 
ducts in a recirculating fashion. 
Vehicle body paint bake ovens of the type described above are 
conventionally fabricated at the factory site where the oven is to be used 
and, as such, considerable erection time and costs are normally involved 
with such ovens. Also, the fabrication of the oven at the factory site 
often results in gas leaks that reduce the efficiency of the oven and emit 
contaminated gas to the factory atmosphere. Deflection of the heated gas 
upwardly from the floor of the oven housing also creates a turbulence that 
picks up dust and dirt particles which can adhere to the wet paint on the 
vehicle bodies prior to drying and thereby produce defects when the paint 
finally dries. To overcome this problem, radiant heaters have been 
utilized in the oven at its upstream end just downstream from where the 
vehicle bodies are spray painted. Radiant heating of the vehicle bodies 
thus initially dries the paint without the use of circulating heated gas 
that can carry dust or dirt particles to the wet paint. 
Further problems arise from the prior art ovens being rectangular. The 
ovens are made from insulated panels connected at joints and are supported 
from an I-beam frame. Condensation of paint fumes saturate the panels at 
the joints. This condition increases heat losses and creates a potential 
fire hazard. 
STATEMENT OF THE INVENTION 
The modular paint bake oven of the invention includes a convection heating 
module having an outer insulated housing. An inner housing of the heating 
module is received within its outer housing and defines a product passage 
through which painted products to be baked are passed in any suitable 
manner such as by conveyance on a floor conveyor or conveyance in a 
depending relationship on a topside conveyor. An upper central supply 
plenum of the heating module is located above the inner housing thereof 
within the outer housing. The inner housing has perforated lateral side 
walls defining a bifurcated gas flow path from the supply penum to the 
product passage. A central upper return plenum of the heating module is 
located above the product passage and below the supply plenum. The inner 
housing has a perforated top wall through which gas flows from the product 
passage to the return plenum in order to permit recirculating flow during 
use.

DETAILED DESCRIPTION OF THE DRAWINGS 
Referring to FIGS. 1 and 2 of the drawings, a paint bake oven 10 in 
accordance with the present invention has a module construction including 
a convection heating module 12. An outer insulated housing 14 of heating 
module 12 has an elongated shape as seen in FIG. 2 along the direction in 
which products are conveyed through the oven from the left toward the 
right. Heating module 12 also includes an inner housing 16 received within 
the outer housing and defining a product passage 18 through which products 
are passed during baking within the oven. An upper central supply plenum 
20 of the heating module 12 is located above the inner housing 16 within 
the outer housing 14 and receives heated gas from a schematically 
indicated recirculating heater 22 such as one of the types disclosed by 
U.S. Pat. Nos. 4,098,567 and 4,324,545. Inner housing 16 of the heating 
module 12 has perforated lateral side walls 24 defining a bifurcated gas 
flow path 26 from the central supply plenum 20 to the product passage 18. 
Gas flows through openings 27 in the side walls 24 upon passing into the 
product passage 18 as illustrated by arrows A. A central upper return 
plenum 28 of the heating module is located above the product passage 18 
and below the supply plenum 20 within the outer insulated housing 14. 
Inner housing 16 has a perforated top wall 30 through which gas flows as 
indicated by arrows B from the product passage 18 to the return plenum 28. 
Paint bake oven 10 including the heating module 12 has particular utility 
when used to bake painted vehicle bodies 32 which are conveyed through the 
product passage 18 on a suitable conveyor 34. During such conveyance, the 
heated gas supplied to the product passage 18 bakes the paint on each 
vehicle body 32 to provide hard and durable painted surface. 
As seen by continuing reference to FIG. 1, the outer insulated housing 14 
of the heating module 12 has a generally round cross-section and includes 
outer and inner sheet metal walls 36 and 38 as well as an intermediate 
layer 39 of a high temperature insulation such as mineral wool. The 
sidewalls 24 of the inner housing 16 of heating module 12 are made of 
sheet metal and preferably have curved shapes that provide the product 
passage 18 with a rounded cross-section. This rounded construction of the 
heating module 12 provides a relatively compact construction that reduces 
heat loss to the environment as well as providing a proximal supply of the 
heated gas flow from the perforated lateral side walls 24 to the conveyed 
vehicle bodies 32. It will be noted that the gas flow is directed directly 
toward the vehicle bodies 32 rather than downwardly and then upwardly as 
is the case with conventional automotive paint bake ovens. Also, the 
modular construction of the heating module 12 permits prefabrication that 
reduces erection costs and also insures a sealed condition so that there 
is no gas leakage to the environment during use. The rounded walls have no 
seams and do not allow the heat loss of prior art rectangular ovens that 
have panels connected at joints. The concomittant fire hazard is also 
alleviated. Further, the round shape provides preferential heat expansion 
characteristics compared to the prior art construction. 
With combined reference to FIGS. 1 and 2, it will be noted that the top 
wall 30 of the inner housing 16 is made of sheet metal and includes 
openings 40 that are formed by a suitable punching operation such that the 
punched portions 42 are located downwardly from the openings. A sheet 
metal adjusting member of the inner housing includes adjusting portions 44 
that are received between the openings 40 and the punched portions 42 to 
provide adjustment of the size of each opening. Movement of the adjusting 
member positions the adjusting portions 44 to control the size of the 
openings 40 in order to thereby control the rate of gas flow through the 
heating module 12. 
With combined reference to FIG. 2, 3 and 4 the inner housing 16 is 
supported in a spaced relationship to the outer housing 14 by a plurality 
of longitudinally spaced supports 46. Each support 46 has a curved shape 
of a generally I beam construction including an outer flange 48 that is 
secured to the outer housing 14 and an inner flange 50 that is secured to 
the inner housing 16. A central connecting web 52 of each support 46 
extends between its outer and inner flanges 48 and 50 and includes 
openings 54 reducing through metal heat conductance to the outer wall. 
As previously mentined in connection with FIG. 1, the recirculating heater 
22 of the oven 10 is mounted on the outer housing 14 of the heating module 
12 above the product passage 18 through which the automotive bodies 32 are 
conveyed. The round cross-sectional structure provides a self supporting 
structure upon which the heater 22 is mounted. Rectangular prior art 
structures could not support the weight of these heaters. As the invention 
is self supporting, the I-beam frame of the prior art assemblies is no 
longer required. Hence, the round cross-sectional structure provides 
several significant improvements over the prior art. A supply duct 56 
feeds heated gas from the heater 22 to the supply plenum 20 of the heating 
module for flow through the bifurcated gas flow path 26 to the products 
chamber 18 as previously described. After baking the painted automotive 
body 32, the gas then passes upwardly through the top wall 30 of the 
product passage 18 into the return plenum 28 as illustrated by arrows B in 
FIG. 1. A return duct 58 (FIG. 2) connects the return plenum 28 to the 
recirculating heater 22 so as to return the used gas from the return 
plenum to the heater for recirculating flow. 
With combined reference to FIGS. 5 and 6, another embodiment of the oven 10 
includes a convection heating module 12' which is similar to previously 
described embodiment except as will be noted. As such, like reference 
numerals are applied to like components thereof and much of the previous 
description is applicable such that no repetition thereof is necessary. 
As illustrated in both FIGS. 2 and 6, each heating module 12 and 12' of the 
oven 10 has an associated exhaust module 64 connected thereto so as to 
receive and exhaust gas from the product passage 18 to the environment. 
Each exhaust module 64 includes a sheet metal housing 66 that defines a 
product passage 68 as shown in FIG. 2 aligned with the product passage 18 
of the associated heating module. Housing 66 of the exhaust module 64 
includes an explosion relief type door 70 that also provides access to the 
interior of the oven for maintenance. Above the product passage 68, the 
housing 66 includes a top wall 72 having openings 74 that are formed by 
punching portions 76 of the wall downwardly. An adjusting member of the 
top wall includes portions 78 that are movable to control the size of the 
top wall openings 74. Any type of suitable exhaust fan is mounted on an 
exhaust duct 79 on top of the exhaust module so as to draw gas upwardly 
through the openings 74 at a controlled rate in order to permit 
introduction of fresh air or inert gas to the oven by the recirculating 
heater 22 of the FIG. 2 embodiments or the fresh air ducts 63 of the FIG. 
6 embodiment. 
With reference to FIGS. 7 and 8, the paint bake oven 10 also includes a 
radiant drying module 80 that initially dries the painted products prior 
to passage through the gas heating module as previously described. As seen 
in FIG. 8, the radiant drying module 80 is located just downstream from a 
spray station 82 at which the vehicle bodies are sprayed painted and has 
an associated exhaust module 64 that is located just upstream from the 
heating module 12 illustrated. Of course, the radiant drying module 80 can 
also be utilized with the heating module 12' previously described as a 
component of the oven 10 and can also be used by itself or with one or 
more other identical radiant drying modules. 
With continuing reference to FIGS. 7 and 8 radiant, drying module 80 
includes an outer insulated housing 84 and an inner housing 86 received 
within the outer housing thereof and defining a product passage 88 through 
which the conveyor 34 conveys vehicle bodies 32 in the same manner 
previously described in connection with the heating modules 12 and 12'. 
Inner housing 86 of the drying module includes a central upper supply duct 
90 and a pair of side passages 92 located on opposite sides of the product 
passage 88. A return duct 94 shown in FIG. 8 is communicated with the side 
passages 92. A heater 96 which is preferably of one of the types disclosed 
by U.S. Pat. Nos. 4,098,567 and 4,324,545 provides heated gas to the 
supply duct 90 of the drying module and receives gas from the return duct 
94 after passage through the side passages 92 to provide radiant heating 
of the vehicle body products 32 that pass through the product passage 88 
on the conveyor 34. 
As illustrated in FIG. 8, each side passage 92 of the inner housing of the 
radiant drying module 80 includes longitudinal partitions 98 that define a 
plurality of longitudinal runs 100 through which the heated gas flows 
parallel to the product passage through which the products are conveyed 
for radiant heating. The gas initially flows from the supply duct 90 to 
the upper run 100 for flow toward the left prior to passage to the lower 
run 100 for flow back toward the right. At the right terminal end of the 
lower run 100, the gas is received by the lower end 102 of an extension 
104 of return duct 94 so as to flow upwardly therethrough back to the 
heater 96 as previously described. 
As illustrated in FIG. 7, the outer housing 86 of drying module 80 has a 
generally round cross-section and includes outer and inner sheet metal 
walls 104 and 106 as well as an intermediate layer 108 of a suitable high 
temperature insulation such as mineral wool. Inner housing 86 of the 
drying module is fabricated from sheet metal and its side passages 92 
preferably have curved shapes so as to provide the product passage 88 with 
a rounded cross-section. Side passages 92 of the inner housing 86 are also 
preferably spaced from the outer housing 84 a slight extent so as to 
thereby lessen heat loss to the environment from the inner housing and 
thereby provide efficiency in operation. Suitable supports may extend 
inwardly from the outer housing 84 to the inner housing 86 in order to 
provide support thereof in the spaced relationship shown. 
As illustrated in FIG. 8, a recirculating fan 110 of the drying module 80 
receives gas from the return duct 94 through a feeder duct 112 and 
delivers this gas through a duct 114 to between the outer housing 84 and 
side passages 92 of the inner housing 86. Feeder duct 112 has a fresh air 
filter 116 through which fresh air is supplied to the recirculating fan 
110 and also has a damper 118 that controls the rate of gas flow through 
the recirculating fan. Such gas flow prevents the buildup of hot gas 
between the outer housing 84 and the side passages 92 of the inner housing 
86 and thereby decreases the heat flow to the environment through the 
outer housing 84. 
Another embodiment of the present invention is shown in FIGS. 9 and 10. The 
paint bake oven shown is similar in construction to the oven shown in FIG. 
5 and like numerals designate like structures. This embodiment of the 
invention includes gas flow control means for covering at least a portion 
of the perforated side walls 24 to direct the flow of gas into selected 
portions of the inner passageway 18. The gas flow control means includes a 
plurality of removable baffles 122 covering at least some of the 
perforations or openings 27. 
As shown in FIG. 9, the removable baffles 122 may cover all the openings 27 
so that the oven is effectively a radiant type oven. In this form, the 
heat from the gases flowing in the gas flow path 26 radiate through the 
side walls 24 and removable covers 122 into the product passageway 18. 
Alternatively, as shown in FIG. 10, the removable covers 122 may be used 
to cover selected portions of the perforations 27 in various portions of 
the module so as to direct heat by convection to portions of the product 
passing through the product passageway and to direct heat radiantly to 
other portions of the product. Further as shown in FIG. 10, the assembly 
may include a plurality of modules, the gas flow control means covering 
selected portion of the perforations 27 in each of the modules to direct 
the flow of gas into various selected portions of the inner passageway of 
each of the modules. In this manner, the oven assembly has great 
flexibility as operating as a radiant type oven, a convection type oven, 
or a combination of both. 
While the best mode for carrying out the invention has been described in 
detail, those familar with the art to which this invention relates will 
recognize various alternative designs and embodiments for practicing the 
invention as defined by the following claims.