Air impingement oven

An oven for continuous cooking of products carried upon a open mesh wire conveyor provides the impingement of a cooking vapor from air discharge structure having ports arrayed above and below the conveyor. The discharge ports extend laterally of the conveyor and communicate with upper and lower plenums each charged by blower fans which draw cooking vapor from low pressure corridors alongside the product conveyor. Gas, electric or thermo fluid heaters are disposed in the corridors. The discharge ports are in slot form disposed about the apex of a Vee shaped riser spaced from the adjacent riser to provide a low pressure flow channel communicating with the corridors giving a rapid velocity change of the cooking vapor from turbulent to a less turbulent flow. The distance for vapor travel between the upper discharge ports and the product carrying conveyor is variable. Temperature and moisture content of the process vapor can be changed to suit cooking conditions.

FIELD OF THE INVENTION 
This invention is concerned with cooking food products and is particularly 
directed to cooking by impinging a process cooking vapor at a 
substantially uniform rate upon food products carried by a conveyor belt 
so that products at various positions on the belt are cooked at 
substantially the same rate with little if any overcooked or undercooked 
products. 
BACKGROUND OF THE INVENTION 
Use of impingement heating apparatus for thermally treating food products, 
such as in cooking or thawing, has been disclosed in the prior art. These 
conventional apparatus typically employ columniating jets of 
temperature-controlled gas which impinge against the surface of a food 
product moving relatively thereto. Such devices are disclosed, for 
example, in U.S. Pat. Nos. 4,525,391, 4,338,911 and 4,154,861. When used 
for cooking purposes, certain of these devices are employed in combination 
with microwave generators for the apparent reason that impingement 
cooking, by itself, is not entirely satisfactory and needs supplementation 
from other cooking equipment. 
In conventional conveyorized ovens which utilize impingement eating, high 
velocity jets of a temperature-controlled gas are directed against the 
surface of food products transported through the oven on a conveyor. The 
temperature controlled gas, or cooking vapor, is discharged from a blower 
or fan into a plenum or enclosed ducts that directs the flow of vapor into 
a series of spaced-apart ducts extending transversely across the conveyor. 
These ducts are in turn adapted to direct the flow of gas into 
columniating orifices which causes the gas to impinge against the surface 
of the food products. These ducts are difficult to clean and require extra 
effort in the clean up operation with close attention to the details of 
complete cleaning required in the process food industry. 
Furthermore, those working with such ovens in the past have encountered 
difficulty in balancing the vapor flow across the plenum and into the 
various ducts, especially those farthest removed from the point at which 
the cooking vapor is discharged from the blower. One result is that food 
products, from side to side on the conveyor belt, are exposed to the 
cooking vapor at uneven rates resulting in certain products which are 
fully cooked, others overcooked and yet others substantially undercooked. 
This is typical where the gross cooking vapor flow is transversely to the 
movement of the product. Non uniformity is another result with the color 
variations indicating uneven cooking of the product from one side of the 
belt to the other. This is apparent when viewing the loaded conveyor belt. 
Such a situation gives an unacceptable standard for application in high 
quality commercial production operations and often leads to a great deal 
of wasted product rejected by the quality control department. Undercooked 
meats such as hamburger patties can carry live bacteria including E-coli 
which are very unsafe to human health. 
Plenums or cooking air ducts positioned on the outside of the conventional 
commercially available impingement ovens are fed from a blower or fan 
typically arranged inside a shroud at the side of the principal air 
delivery plenum or enclosed duct. These ducts collect dirt such as grease, 
crumbs and other deposits from the cooking operations which must be 
cleaned out periodically. And moreover, in the use of the single blower 
assembly, consisting typically of a fan wheel and a fan drive motor, 
attempts have been made to balance the flow of cooking air into the 
distribution ducts farthest removed from the blower by tapering the walls, 
thus diminishing the cross-sectional area of the ducts. This is not 
entirely effective. In an attempt to balance or control air flow as 
between the streams directed to the top and to the bottom of the product, 
dampers are often employed in the external, enclosed ducts. Although 
dampers in the air distribution system may serve somewhat the objective of 
air flow balance, they cannot either increase or decrease the overall mass 
flow in the oven. The single blower is the limiting factor. 
It has been found in the prior art that the interior oven surfaces between 
the air discharge orifices and the blower or fan intake cause turbulence 
within the cooking chamber. This further disrupts the return flow of the 
treatment vapor and even hinders the efficient heat distribution of the 
treatment vapor emitted from the orifices onto the product. It will be 
understood that after the cooking gases have issued from the orifices and 
impinged upon the product, ideally the gases should be removed as 
efficiently as possible from the vicinity of the product in order that the 
cooking gases following behind will be permitted to engage the product and 
not be obstructed by stagnant or disordered circulation zones created 
within the oven proper. That situation or condition is undesirable from 
the standpoint of achieving efficient heat transfer from the circulating 
treatment air onto the products being cooked. 
Following a completed cooking cycle the oven is cleaned and in many oven 
models this is a labor intensive process which absorbs considerable non 
operating or down time for the oven. Vapors and juices created in the 
cooking process frequently are deposited on the interior walls of the oven 
as well as in the vapor distribution ducts and requires an opening up of 
the oven for cleaning and visual inspection. A highly desirable feature in 
an oven is the ability to clean the unit without necessarily opening up to 
expose the oven interior and with a highly reduces reliance on manual 
cleaning. 
In view of these and other disadvantages that have been encountered in 
using the conventional, commercially available oven apparatus, an improved 
duct-less impingement oven is needed that will facilitate even 
distribution of the food treatment vapors across the conveyor belt for 
more even heat application to the products carried thereon, an oven which 
will afford substantially reduced turbulence therein, and wherein the 
return flow of the cooking vapors to the fan for the reticulation cycle 
will be within the oven proper and not through the hard to clean, usually 
invisible, interior surfaces of outside plenums or ducts. 
SUMMARY OF THE INVENTION AND OBJECTS 
According to the present invention, an improved impingement heating 
apparatus is provided without any outside ducts which comprises novel oven 
construction including an arrangement of oven elements adapted to provide 
substantially uniform side-to-side cooking gas distribution at very 
uniform velocities from nozzles unto the food products being treated. 
According to one object of the invention, a novel arrangement of chambers 
is provided entirely within the oven shell that significantly improves the 
distribution of the process cooking vapor from upper and lower blowers or 
circulation fans, disposed to charge upper and lower chambers, with each 
blower's intake being arranged so as to receive circulated vapor from 
low-pressure corridors within the oven housing so that the vapor is 
channeled for good side-to-side cooking uniformity and wherein the gross 
flow of the cooking vapor is parallel to the product movement through the 
oven. 
Another object of the invention is to provide an impingement oven wherein 
the circulation fans are located inside relatively higher-pressure 
chambers, eliminating the need for separately ducting the process vapor, 
for impinged onto the product through an array of nozzles in a manner that 
after discharged through the nozzles, the process vapor is circulated 
towards the outer side margins of the conveyor belt in a flow of much 
reduced turbulence and thereafter the vapor is directed into the intake of 
the circulation fans for reticulation. 
Another object of the invention is to provide an oven of the type described 
wherein lower-pressure vapor reticulation channels are provided adjacent 
the oven side walls on each side of the nozzle arrays. 
Still another object of the invention is to provide an air impingement oven 
wherein both the higher and lower pressure chambers are easily exposed for 
inspection and cleaning without the use of hand tools or the use of 
inspection doors. 
Still another object of the invention is to provide in an oven of the type 
described means for independently controlling the mass flow of process 
vapor into the upper and the lower chambers without resort to dampers or 
air flow diverter baffles or the like. 
In accordance with the foregoing object, independently controllable fans 
positioned in the upper and lower chambers permit a wide range of 
circulating vapor mass flow rates between the upper and the lower chambers 
and thence through the nozzles associated therewith. 
Another object is to provide a design which enables process vapor 
circulation generally parallel to the product movement on the conveyor 
belt and affording very uniform vapor velocities transversely of the 
conveyor belt through impingement nozzles which are configured to provide 
very high nozzle efficiency while allowing for optimum return volume for 
the reticulated vapor to flow in an efficient flow pattern. 
Mother object of the invention is to provide an impingement nozzle 
structure in which the distance may be varied between the product and at 
least one of the nozzle sets. 
Yet another object is to provide in the oven of the type described a 
conveyor belt support structure which co-acts with the lower impingement 
nozzles so as to maintain them in a sealing relationship with their 
associated higher pressure chamber. 
Still another object is provide in an oven of the type described a 
clean-in-place system which uses the blower fans, as well as all other 
vapor distribution and circulation elements, to circulate a cleaning 
solution and a rinse solution through out the oven while affording the 
ability to regulate the cleaning time and temperature through use of the 
oven controls. 
A further object is to provide an cooking process in an oven of the type 
described which admits a distinctive food flavoring constituent into the 
process cooking vapor so that the distinctive flavor may be imparted to 
the food product during the cooking cycle. 
In connection with the above object it is intended to provide a smoke-house 
cooking process operating in the impingement oven disclosed herein for 
preparing link sausages, frankfurters and other products normally cooked 
in a smoke-house. 
In summary, the invention comprises a high-speed air impingement oven with 
an outer housing equipped with product inlet and product outlet means. A 
product conveyor extends through the inlet and outlet. An inner housing is 
arranged within said outer housing and is dimensioned laterally so that 
its sidewalls are spaced apart from the adjacent sidewalls of the outer 
housing thus to define longitudinally extending low-pressure corridors 
along each sidewall of said inner housing. The inner housing comprises 
upper and lower chambers disposed above and below a conveyor belt and fan 
circulation means are arranged in said upper and lower chambers so that 
the fan inlets communicate with the low-pressure circulation corridors and 
the fan outlets communicate with the interior of the upper and lower 
chambers respectively and thereby serve to create therein a zone of 
relatively higher pressure. Nozzle arrays extend transversely of and 
project in a generally perpendicular direction towards the product 
conveyor belt from said upper and lower chambers with each nozzle array 
including a plurality of parallel risers spaced apart along the belt with 
each riser projecting away from the base portion in a taper merging into a 
substantially narrower distal surface extending laterally of and proximate 
to said conveyor belt. The narrower distal surface is provided with a 
skewed line of vapor discharge slots therein. Heating means and steam 
releasing means are provided in the housing and regulated to maintain a 
controlled temperature of the cooking vapor discharged from the nozzles. 
Further objects and advantages of the invention will appear from a 
consideration of the illustrative drawings taken in connection with the 
detailed description which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2 of the drawings, there is shown an improved 
high-speed air impingement oven 10 made in accordance with and embodying 
the principles of the present invention. The impingement oven 10 includes 
a product inlet zone 11, a product outlet zone 12 and a continuous 
conveyor belt 13 of open mesh wire construction which extends through the 
inlet zone 11, through the oven body and through the outlet 12. The 
conveyor is shown configured for an outside belt return with provisions on 
the outside return run for cleaning the surface of the conveyor belt 13 
through use of rotating brushes and cleaning liquids as is well known in 
this field. An inside return (not shown) for the conveyor belt 13, whereby 
the conveyor is almost entirely contained within the oven housing, 
provides efficiencies in certain applications and can be adopted without 
departing from the scope of this invention. 
Both the oven inlet 11 and outlet 12 are provided with shroud means 14 
which include an exhaust stack 16 equipped with a damper 17. When the oven 
10 is installed in the food processing plant, each stack 16 is provided 
with air suction means (not shown) to furnish an up-draft so as to 
withdraw ambient air through the inlet 11 and outlet 12 as well as a 
modicum of process vapor from the oven interior and to move the vapor up 
the stacks 16 so as to materially reduce the uncontrolled entry of ambient 
air into the cooking process carried on within the oven 10. Moreover, the 
continuous process carried on within the oven is thus controlled so as to 
be confined substantially within the oven cooking chamber while permitting 
very little in the way of emissions to escape into the food processing 
plant. 
Referring particularly to FIG. 2, the oven 10 is configured to include an 
inner housing 21 and an outer housing 22. The outer housing 22 is 
supported on a frame 19 which includes vertical legs 23 and 24. The legs 
are equipped with upper housing lifting means 26 which serve to permit the 
hood 27 or upper oven portion to be raised selected distances to dispose 
the air impingement means therein at selected distances from the product 
(as will be described more fully below) and to be fully raised, separating 
the upper and lower oven portions, to facilitate visual inspection of the 
oven interior for periodic cleaning and maintenance work as is well 
understood in the field. The hood 27, includes a skirt 28 disposed at the 
lower margin of the hood sidewalls. A water holding trough 29 extends 
about the perimeter of the oven's cooking zone and furnishes a water seal 
between the upper 27 and lower 30 oven structures when in the closed 
condition as for cooking. The trough 29 is mounted on the oven frame 19 
and positioned so that the skirt 28 of the hood 27, in the closed 
operative condition of the oven, extends into the trough 29. Normally, 
during oven operations, the trough 29 is filled with water. Similarly, the 
lower oven structure 30 is equipped with a flange portion 31, which 
extends into the trough 29 to effect sealing of the housing so as to 
contain the process cooking vapor to the cooking zone therein. Should an 
over-pressure develop within the housing, water in the trough would rise 
or would be expelled. The water seal thereby functions as a safety 
provision against an inadvertent over-pressure condition within the 
cooking zone within the oven. As may be seen from FIG. 3, the water seal 
between the hood and the lower oven structure 30 is provided on the 
lateral or end walls of the oven as shown to the right of FIG. 5. 
As shown in FIG. 2, the inner housing 21 of the oven is configured so that 
its longitudinally extending sidewalls 36 and 37 are spaced laterally 
inwardly of the corresponding sidewalls of the outer housing 22. This 
spacing affords on each side of the oven interior a corridor 39 extending 
substantially the full cooking length of the oven. 
Heating means 41, which may comprise gas or oil fired radiant tubes, are 
arranged in the corridors 39, the tubes 41 having a serpentine 
configuration as shown clearly in FIGS. 1 and 3. The heating means 
terminate in exhaust stacks 42, which serve to carry the products of 
combustion out of the food processing plant in which the oven 10 is 
located. Alternatively, the oven heating means 41 may comprise electric 
resistance or cal rod heaters (not shown), direct open flame or a thermal 
fluid heat exchanging system and these heating means are well-known in the 
field. With suitable controls well known in the art, the oven may be 
heated to operate at temperatures from as low as 100 F to as high as 600 
F. 
In the lower oven housing 30, the sidewalls 36, 37 are sealingly united to 
the bottom wall 15 of the outer housing. In the hood 27 or upper section 
of the oven, sidewall 36, 37 are sealingly united to the top wall 20 as 
shown best in FIG. 2. A lower nozzle plate assembly 44 is mounted with 
respect to the sidewalls 36, 37 in the lower portion of the oven 30. Taken 
together, the nozzle plate assembly 44, the sidewalls 36, 37 and the oven 
bottom 15 serve to define a lower chamber disposed inwardly of the side 
corridors 39. 
To eliminate the need for clamping or bolting the nozzle plate assembly 44 
to other oven structure in order to achieve an air seal with respect to 
the lower chamber, a novel arrangement has been devised. More specifically 
and referring to FIG. 2, the product conveyor support frame 13a and 13b of 
the belt conveyor 13 rests directly up on the nozzle plate assembly 44 
insuring that margins of the plate assembly maintain sealing contact with 
the associated structures of the side walls 36, 37. Vertically extending 
support rods 40,45 are connected to the conveyor support frame and attach 
at their upper portions to the elevatable portions of the upper housing. 
As mentioned, the upper oven portion may be raised and the conveyor 
structure is as attached so as to move therewith. When raised the 
conveyor's weight is removed from the nozzle plate assembly 44 and it too 
can easily be dismounted for inspection or cleaning. 
An upper nozzle plate assembly 46 is mounted with respect to the sidewalls 
36, 37 in the upper portion of the oven and can be raised and lowered with 
the upper housing portion for selectively positioning the nozzles 
vertically a variety of desired distances, for example in a range of 2 to 
8 inches, from the conveyor belt 13 and the products carried on it. Thus 
the intensity of air impingement upon the products can be varied and the 
treatment of the products can be controlled even while the oven is in 
operation. The upper nozzle assembly 46, together with the upper inner 
sidewalls 36, 57 and oven top 20 serve to define an upper chamber 47 
disposed inwardly of the longitudinally extending side corridors 39, as 
shown clearly in FIG. 2. It will be seen from FIG. 2 that the lower 
horizontally extending portions of the sidewalls 36, 37 are equipped with 
in turned channel flanges 36a and 37a. The nozzle plate assembly 46 is 
equipped along its upper sidewall portions with outwardly turned channel 
shaped flanges 46a and 46b. The flanges are configured to nest in flanges 
36a and 37a so that when the upper chamber is pressurized during fan 
operation the cooperating flanges 36a,37a,46a and 46b establish a seal 
between the nozzle plate and the chamber side walls thereby permitting a 
pressure differential to be created and maintained in the upper chamber 47 
with respect to the corridors 39 or other portions of the oven. 
A dual wheel, axial flow fan or blower assembly 48 is mounted in the lower 
chamber 45 and is arranged so that a fan air supply inlet 49 opens through 
each sidewall 36, 37 so that the blower 48 may withdraw air from the two 
side corridors 39 and discharge process vapor, as indicated by the arrows 
50 in FIG. 3, into the lower chamber 45. The impeller for the fan or 
blower assembly 48 is mounted on a drive shaft 51, which is journalled in 
a centrally disposed bearing 52, which is mounted, for cooler operations 
on a central enclosure outside of the cooking environment, and an outside 
side bearing 53. An alternate construction is to rotatably support the 
impeller on a shaft mounted in outboard disposed bearings, it being 
understood that the cross-section of the shaft is selected to withstand 
the kinetic forces encountered in normal oven operation. A circulation fan 
satisfactory for the purposes of this invention is Model No. PRL 22, made 
by The New York Blower Company, 7660 S. Quincy St., Hinsdale, Ill. 60521. 
The drive shaft 51 is driven from a motor 52 disposed outside of the outer 
housing. A motor satisfactory for the purposes of this invention is Model 
No. EB0254FFA, having a power rating of 25 HP, and made by Sterling 
Electric Motors Incorporated, 799 Rennie St. Hamilton, ON L8H 3R5, 
Ontario, Canada. The horsepower of the motor 52 is sufficient to move a 
substantial volume of process vapor (20,000 cubic feet per minute per 
blower assembly) at a pressure differential of 4 inches of water column 
between the outer corridors 39 and the lower chamber 45 at operating 
temperature. The process vapor issues through the vapor impingement nozzle 
assembly to be described in more detail below. 
The upper chamber 47 is also provided with a dual wheel, axial flow blower 
fan 48 with air inlets 53 opening through the sidewalls 36, 37 so as to 
permit the heated process vapor to be withdrawn from the side corridors 39 
for discharge into the upper chamber 47 as indicated by the arrows 50 in 
FIG. 3. The impeller for the fan 48 in the upper chamber 47 is mounted on 
a drive shaft 56 supported by bearing assemblies 57, 58 and driven from an 
electric motor 52. The motor 52 and blower 48, which may have the same 
operational characteristics as described above, function to withdraw 
process vapor from the side corridors so as to positively charge the upper 
chamber 47 with a constant supply of process vapor for discharge through 
the upper nozzle plate assembly 46. The operating pressure differential, 
normally 4 inches of water column, between the upper chamber 47 and the 
side corridors 39 may be regulated over a desired range by appropriate 
adjustment of the impeller rotational velocity through regulation of the 
driving speed of the motor 52. 
Although we have illustrated one preferred location of the circulating fans 
48 at nominally one end of the oven, we have found it to be equally 
practical to mount the fans in a central location of the oven, say midway 
along the oven length which would be the case when two of the ovens 10 are 
mounted end to end with the fans 13 in the center. 
Referring to FIGS. 4, 5 and 6, the nozzle array structures 44, 46 contain 
the air distribution ports and comprise a plurality of Vee-shaped risers 
61 which extends transversely of the conveyor belt 13. The risers 61 are 
spaced apart longitudinally of the belt, a distance approximately equal to 
5/8ths of their height as measured from their base plate 62. That is to 
say, for example, should the risers be eight inches tall their spacing 
would be at a five inch pitch which would be typical for an oven with a 40 
inch wide conveyor belt spanned by the structures 44, 46. Other spacings 
are useful so long as the configuration affords a substantial cross 
sectional flow area between successive risers 61 and affords a 
low-pressure flow channel 63 which extends laterally across the riser 
assembly and communicates with the corridors 39 permitting process vapor 
to flow in the direction of the arrows 64, as shown in FIG. 6, at a 
velocity of about 1000 to 1500 feet per minute. The risers 61 taper from 
the base plate 62 to the aligned air discharge ports or slots 66 from 
which the process vapor exits from the plenum or chambers 45, 47 in the 
direction of the arrows 67, as indicated in FIGS. 4 and 6. It will be 
understood that the risers are ever decreasing in cross sectional area 
from the base plate 62 to the flow ports 66 and consequently the air 
velocity increases considerably in accelerated flow from the base plate to 
the discharge slots 66. A useful set of dimensions for the ports 66 is on 
the order of 5/16.times.1 inch placed on 11/4 inch centers across the apex 
of the riser. The discharge ports or slots 66 are staggered from riser to 
riser as viewed longitudinally of the belt as shown in FIG. 6. The 
objective and purpose of this configuration is to permit controlled 
turbulent, long duration contact of the cooking gases with the products. 
Furthermore, in another preferred embodiment, some of the ports or slots 
66 may be set at an angle (not shown) from the apex line so that one slot 
discharges in a vertical plane, the next slot discharges in a plane at an 
acute angle to the right and the next slot 66 discharges in a plane at an 
acute angle to the left of the apex line. The next slot is situated on the 
apex line and the sequence is repeated. This produces a scatted jet effect 
in the controlled turbulent, long duration contact of the cooking gases 
with the food products. 
The process vapor discharges at a high velocity, on the order of 9000 feet 
per minute, through the slots 66 as indicated by the arrows 67 and 
impinges against the food product 68 supported on the conveyor belt 13, 
FIG. 4. The food product 68 maybe, for example, sausage, chicken patties, 
beef patties, meat loaf, meat balls, tortilla chips and similar products, 
chicken portions or even slices of bread being made into toast. 
In summary, to set into operation the air impingement oven 10, the conveyor 
belt 13 is set into motion in the direction of the arrows 69 and food 
products 68 are arranged on the belt for cooking or other treatment, and 
are carried into the oven through the oven product inlet 11. The food 
products 68 passes beneath the shroud 14, which serves to maintain the 
inlet end of the oven in a neutral condition insofar as controlling air 
entry or process vapor exit from the oven. The heating unit 41 is actuated 
so as to bring the atmosphere of the oven to the desired operating 
temperature. Provisions are made in the oven for the entry of saturated or 
super heated steam through a steam delivery inlet line 70 as indicated by 
the arrow 71 (FIG. 1) from a source of steam in the operating plant (not 
shown). The steam supply may be regulated to achieve a desired moisture 
content in the process atmosphere in accordance with the principles set 
out in the assignee's issued U.S. Pat. No. 3,947,241, granted Mar. 30, 
1976 and U.S. Pat. No. 4,167,585, granted Sep. 11, 1979. The two fan 
driving motors 52 are set into operation for driving the axial flow, dual 
wheel blowers 48 so as to withdraw process vapor from the side corridors 
39 at the rate of about 1900 feet per minute as it moves towards the fan 
inlets 49, 53 for charging the upper and lower chambers 45, 47 with 
process vapor at a relatively higher pressure than that which exists in 
the corridors 39. The heated process vapor exists the chambers 45, 47 as 
impingement flow through the discharge slots 66 disposed at the tip or 
apex of the risers 61 at a velocity of about 9000 feet per minute. The 
process vapor, moving in the direction of the arrows 67, impinges against 
the food product 68 disposed about 2 inches from the nozzles and residing 
on the open mesh wire conveyor belt. This spacing can be varied to suit 
product cooking conditions. The heated process vapor engages the product 
in a rapid, turbulent flow and then abruptly moves away from the product 
carrying belt 13 into the deep return channels 63 disposed intermediate 
consecutive risers 61 in the flow pattern suggested by the broken lines 
65, FIG. 4. Movement of the process vapor in the direction of the arrows 
64, FIG. 6, is relatively less turbulent in flow due to the substantial 
depth of the channels 63 and the volume available therein for containing 
the process vapor which drops substantially in intensity and velocity 
before returning to the blower inlet in a reticulation pattern. The heat 
transfer efficiencies are unexpectedly high due to, it is believed, to the 
change in the direction of the acceleration of the vapor flow while in 
contact with the product and the reduced return velocities shortly after 
contact with the product. In the prior art ovens, it was found to be 
common to produce uneven cooking of the food products dispersed in various 
locations along the belt and this problem has been overcome in the subject 
oven 10. 
The position of the upper nozzle assembly can be set at several different 
elevations with respect to the conveyor belt 13 when desired for adjusting 
and controlling the intensity of the vapor impingement upon the food 
products. A very useful range of nozzle distance from the products carried 
upon the belt 13 is between 2 and 8 inches. As mentioned above, the upper 
nozzle plate assembly is arranged to move in unison with the upper housing 
portion, the unit being lifted by the jack assemblies mounted in the legs 
26. This capability together with the ability of selectively changing the 
speed of the conveyor belt and fan assemblies, the temperature and 
moisture content of the process vapor, affords excellent control over the 
cooking processes. 
The food products are removed from the oven through the outlet shroud 14 
and are removed from the outlet 12 for further processing such as cooling, 
chilling and packaging as is pertinent to the individual products, of 
which there are many, that can be treated within the oven 10. 
A highly effective process step for imparting a smoke flavor to a food 
product cooked in the oven 10 is to introduce liquid smoke or a similar 
flavoring into the oven during the cooking process. A smoke generator and 
its constituents of a conventional type normally associated with a smoke 
house (not shown) is connected to the oven so as to inject the 
concentrated flavoring material either at the intake throat or on the high 
pressure side of at least one of the blower fans 48. The flavoring 
material is quickly completely vaporized and is carried along in the 
process vapor where in contacts the product at a high velocity and is 
hereafter reticulated to repeatedly contact the product. The amount of 
flavoring material injected into the process stream is controlled so that 
neither over-flavoring or under flavoring is found in the product. Because 
the flavoring is distributed to the products laterally as the conveyor 
belt moves through the oven 10, there is a uniformity of treatment from 
side to side of all products on the belt. Thus there are very, very few 
products which are over flavored or over cooked as well as the converse 
situation in the operation of the impingement oven 10. Sausage (both link 
and paddy form), frankfurters, ribs and the like products usually prepared 
in a smoke house cabinet can as well be cooked in the subject process and 
oven. 
EXAMPLES 
Examples of products which have been successfully cooked within the oven 10 
include sausage patties formed into a 3-inch diameter round shape, 
approximately 3/8-inch in thickness with a raw weight of 58 grams. The 
patty was cooked with very good color and yield with a cook time of 1.5 
minutes. The oven temperature, dry bulb, was 425.degree. F. and the wet 
bulb temperature was 205.degree. F. or 80 percent moisture content in the 
process vapor. The product temperature was 158.degree. at the end of the 
test with a yield of 86 percent. 
Sausage patties were cooked for 1.5 minutes in a batch of 12 pieces having 
a weight of 744 grams in another example. The internal temperature of the 
patties at the beginning of the cook run was about 30.degree. F. The 
impingement oven was operated at 325.degree. F. dry bulb temperature with 
the process atmosphere of about 70 percent moisture. The impingement 
nozzles were positioned 2 inches from the belt 13 and the fan blowers 
operated at 35 percent of their rated capacity. The product internal 
temperature at the end of the cook run was in the range of 160-165.degree. 
F. and the final product weight was 668 grams giving a yield of 89.8 
percent. The product size was a patty initially of about 3.75 inches by 
4.5 inches by 5/16 inches in thickness with a nominally 60 grams each raw 
weight. In another example, patties of a similar size and weight were 
cooked in the oven disclosed herein in a batch of 29 pieces with an 
initial weight of 1767.5 grams and having an internal temperature of 
42.degree. F. The cooking time was 0.8 minutes with a dry bulb temperature 
of 525.degree. F. and a 20 percent moisture content of the process 
atmosphere. The nozzles were positioned at 2.2 inches from the conveyor 
belt and the fan speeds were maintained at 95 percent of operational 
capacity. The product exit temperature was in the range of 165-175.degree. 
F. with a batch weight of 1460 grams affording a yield of 82.6 percent. 
The patties were light to medium brown in color and the yield was 
considered acceptable. The color characteristics of the product was 
uniform across the conveyor belt. 
As a further example, beef and pork meatballs were cooked with the oven 
apparatus of the present invention. Meatballs, because of their thickness 
and generally spherical configuration, cannot be cooked with high oven 
temperatures and high fan speeds as this would produce a product that was 
too dark on the outside and either under or overcooked on the inside, 
depending on the dwell time. However, meatballs were cooked to a good 
color with a uniform internal temperature across the belt and comprised a 
batch of 1/2 ounce meatballs with a total weight of 621 grams. The batch 
had an internal temperature in the range of 42-50.degree. F. The cook time 
was 2.5 minutes with an oven temperature of 400.degree. F. dry bulb at 60 
percent moisture of the circulating atmosphere. The nozzle height was 3 
inches above the belt and the fan speed was 85 percent on the upper fans 
and 80 percent on the lower fans. The exit product temperature internally 
was in the range of 166-168.degree. F. The exit batch weight was 5253 
grams with a yield of 84.6 percent. 
An example of an application where the oven of the present invention can be 
used to develop surface color in a short period of time concerns a chicken 
product. This product was a boneless, skinless chicken breast and the 
chicken meat was marinated with a mesquite flavored marinade. A batch of 4 
pieces weighing 830 grams and having a 45.degree. F. internal temperature 
had been precooked in steam to have an internal temperature in the range 
of 95-118.degree. F. Then the products were introduced into the oven of 
the present invention for a very short cook time of 0.8 seconds. The oven 
temperature was 540.degree. F. dry bulb with 45 percent moisture content. 
The nozzle spacing was 2.2 inches and the fans operated at 100 percent of 
rated speed. The product exit temperature was in the range of 
150-175.degree. F. with a product weight of 718.7 grams. The yield was 
85.6 percent. Even at the short dwell time of 0.8 minutes, the product had 
a very good color lending an appetizing appearance to the product. 
The oven of the present invention can be used to perform a process like 
that performed in the conventional smoke house. More particularly, in a 
smoke house the product is "soaked" in a relatively low temperature heat 
environment for a substantial period of time so that the product can 
absorb the smoke to impart the desired color and smokey aroma to the 
product. A chicken product comprising cornish hen halves were successfully 
treated to have the desired color aroma and smokey taste. The initial 
product weight was 27 grams at an initial temperature of 46.degree. F. The 
cooking time was 21 minutes, in two oven passes, with a dry bulb 
temperature set intially at 260.degree. and for the second pass at 
300.degree. F. The air delivery nozzles were positioned at a height of 6 
inches from the product and the fan speeds were 45 to 50 percent of 
capacity. A smoke generator introduced the smoke material into the inlets 
of the oven blower fans through the nozzles 101, as shown in FIG. 2. Exit 
temperature of the product was between 178 and 190.degree. F. and the 
yield was 76 percent. The cooking time is substantially shorter than if 
the product were cooked in the conventional smoke house cabinet. The 
foregoing technique has also been successfully used in connection with 
sausages in a cellusosic casing as well as with frankfurters. The heat 
transfer in the oven 10 and the smoke application sets the product into 
the desired texture with an acceptable appearance and it is cooked to the 
desired end temperature. 
Yet another example of a process enabled by the present invention is one of 
comparatively slow cooking of a product such as whole meatloaf. The 
meatloaf product had an initial temperature of 45.degree. F. and a weight 
of 197 grams. The dry bulb temperature of the oven was 300.degree. F. and 
the wet bulb set at 55 percent moisture content. The nozzles were spaced 6 
inches from the product carrying belt and the fans operated between 45 and 
50 percent of their capacity. The total processing time of the product in 
the oven was 43.2 minutes, in four runs of about 10.8 second each. The 
product exit temperature was at the desired 166.degree. F. and the yield 
was 82 percent. 
From the above examples and description of the oven, it should be readily 
apparent that the oven system described herein provides rapid heat 
transfer to food products and that the heat transfer can be well 
distributed over the surface of irregular-shaped products, such as chicken 
thighs, chicken breasts, meat balls and meat loaf. The heating time can be 
substantially less than that required by other cooking systems and the 
surface color can be readily developed as desired. Smoke flavoring or the 
like can be imparted to food products during cooking in this oven so as to 
develop quickly and accurately the desired smoke flavor even while cooking 
proceeds. 
An important operational feature of the oven 10 is the clean-in-place 
system. Normally, ovens use to process meat containing products or the 
like must be completely cleaned periodically to comply with governmental 
inspections for compliance with hygiene and health regulations. Cleaning 
entails usually at least a partial disassembly and manual scrubbing of all 
oven parts that are coated with grease, burn-on or the like-a labor 
intensive and costly operation in terms of lost production time. The oven 
10, on the other hand, can be substantially cleaned in the hood closed 
condition, as shown in FIG. 2. Cleaning fluid injectors 102 are focused 
into the intake side of the fans 48 (FIG. 2) so as to deposit cleaning 
fluids, on the order of 50 gallons per minute, while the fans are in 
operation. Liquid spray balls 103 positioned at the fan 48 discharge 
distribute the cleaning or rinsing liquid throughout the oven. The action 
of the liquid on the fan blades is shown schematically in FIG. 2a. The 
cleaning fluid may be maintained at a controlled temperature with the use 
of the heating elements 42. Fan speeds are controlled so as to drive the 
cleaning solution to all parts of the oven 10 contacted by the process 
vapor. This causes a removal of grease and other undesirable contaminants 
deposited in the oven from the prior cooking operations. Caustic is an 
ingredient of the cleaning solution and hence a clear water solution is 
used as a rinse to remove the vestiges of cleaning solution before the 
oven is opened for visual inspection and touch-up cleaning where needed. A 
savings of time and labor is made through use of this cleaning process 
which utilizes the operative air generating, heating and circulating 
components of the oven. The nozzles 101 are arranged in a fluid delivery 
circuit couple to an outside source of water pressure. A drain (not shown) 
in the low part of the bottom of the oven serves to remove the cleaning 
and rinse fluids from the unit for either re-circulation by a pump or for 
final disposal. 
The cleaning of the oven can be achieved with the oven halves in the usual 
operating position through a system wherein cleaning solutions are 
injected into the impeller fans so as to establish a cleaning cycle 
followed by a rinse cycle wherein rinsing solutions are similarly 
introduced into the oven Meanwhile, the fan circulating and heating 
components are controlled to achieve an efficient cleaning of all air 
exposed surfaces in the oven. 
While the disclosure of the examples, structure an operation of the cooking 
system herein has been such as to teach those skilled of the art the 
principles of the applicants' development, the true scope of the invention 
shall not be limited except as set out in the claims below.