US3144243A

US3144243A - Ovens

Info

Publication number: US3144243A
Application number: US137196A
Authority: US
Inventors: Henson Thomas Leslie
Original assignee: Baker Perkins Inc
Current assignee: Baker Perkins Inc
Priority date: 1960-09-12
Filing date: 1961-09-11
Publication date: 1964-08-11
Anticipated expiration: 1981-08-11

Description

Aug. 11, 1964 T. L. HENSON OVENS 8 Sheets-Sheet 1.

Filed Sept. 11, 1961 Aug. 11, 1964 T. L. HENSON 3,144,243

OVENS Filed Sept. 11, 1961 8 Sheets-Sheet 3 T. L. HENSON Aug. 11, 1964 OVENS s Sheets-Sheet 4 Filed Sept. 11, 1961 Aug. 11, 1964 T. L. HENSON 3,144,243

OVENS Filed Sept. 11, 1 961 s Sheets-Sheet 5 Tfiii m l /vl'mc 75 41/45 [554/5 522/549 Aug. 11, 1964 T. L. HENSON OVENS 8 Sheets-Sheet 6 Filed Sept. 11, 1961 Aug. 11, 1964 T. L. HENSON OVENS 8 Sheets-Sheet 7 Filed Sept. 11, 1961 Aug. 11, 1964 -r HENsoN OVENS 8 Sheets-Sheet 8 Filed Sept. 11, 1961 m m 2 w Qw WE J I I I I I J M w 4 n m T/ li 7 E 2%; Ex 1 HIKKKVT Q IIIIIIII w 5C3:EL n i: 11 5 k l w United States Patent i 3,144,243 OVENS Thomas Leslie Henson, Peterborough, England, assignor to Baker Perkins Incorporated, Saginaw, Mich. Filed Sept. 11, 196i, Ser. No. 137,196 Claims priority, application Great Britain Sept. 12, 1960 It} Ciaims. (Cl. 263-6) This invention relates to ovens in which articles being treated therein are subjected to radiant or forced convection heat, or both.

An object of the invention is to provide an improved method of heat treating articles, and oven means therefor, in which the forced convection heat medium is delivered on to the articles at a selected velocity.

A further object of the invention is to provide an improved oven means employing a combination of radiant and forced convection heat in which the forced convection heat medium is caused to experience heat exchange from the radiant heating means prior to delivery into the oven heat treating chamber.

The invention consists in a method of and means for heat treating articles in an oven which comprises passing the articles along a path in the oven treatment chamber while subjecting the articles to forced convection heat by applying to the articles flows of convection heat medium delivered from close proximity to the path of the articles through the treatment chamber and to radiant heat from radiant heat means spaced on the same level as, or further away from the said path than, said forced convection heat delivery.

The invention further consists in an oven for heat treating articles in which means are provided for supplying forced convection heat medium to the treatment chamber of the oven so as to impinge upon the articles to be treated, the medium being arranged to be heated by the radiant heat means during its passage to the oven chamber and before it enters the chamber.

According tothe present invention it is preferred to employ oven atmosphere as the forced convection heat medium, the oven atmosphere being withdrawn from the oven chamber in known manner, eg through extraction orifices spaced along the oven chamber, and passed through conduit means to the forced convection heat delivery points. Where the radiant heat means are such as to produce products of combustion, the latter is circulated through the radiant heat means and is kept segregated and is not allowed to enter the oven chamber and to mix with the oven atmosphere.

According to one form of the present invention the radiant heat means and the forced convection heat conduit means comprise conduit means located side-by-side and extending along lengths of the baking chamber above and below the path of the articles therethrough, adjacent conduit means preferably having common separating walls and the conduit means being alternately connected to header means whereby the radiant heat conduit means alternate with forced convection heat conduit means.

As stated above, the forced convection heat medium may comprise oven atmosphere extracted from the baking chamber, through orifices along the baking chamber, by means of oven atmosphere extraction conduit means incorporated between certain of the above-mentioned radiant heat and/ or forced convection heat conduit means,

the extraction conduit means being provided with the oven atmosphere extraction orifices and are connected by header means ultimately connected to the header means for the forced convection heat conduit means.

It is preferred, however, to provide suction conduits for the extracted oven atmosphere disposed laterally of the bank of radiant and forced convection heat conduit means, the oven atmosphere being extracted by extrac- 3,144,243 Patented Aug. 11, 1964 tion conduit means extending transversely of the radiant and forced convection heat conduit means at spaced intervals along the baking chamber, having extraction orifices therein and connected at one end of each to the suction conduit at one side of the bank.

According to an alternative form of the present invention the radiant heat means and the forced convection heat means comprise conduit means extending in lengths longitudinally of the baking chamber above and below the path of the articles therethrough and the forced convection heat conduit means have extending transversely across them at spaced intervals suitably shaped duets with spaced orifices, the ducts being disposed against the face or faces of the associated radiant heat conduit means nearest said path so as to be located closer to said path than the radiant heat conduit means.

In all cases the forced convection heat conduit means are provided with outlet orifice means adjacent the path of the articles through the baking chamber, so that forced convection currents of heated oven atmosphere are caused to impinge on the articles in the baking chamber.

In the accompanying drawings:

FIGURE 1 is a perspective view of part of an oven having radiant heating and forced convection heating means associated with the baking chamber, according to the present invention, the forced convection heating circulation system only being fully shown,

FIGURES 2, 3 and 4 are cross sectional diagrams of banks of radiant heating and forced convection heating conduit means, showing different conduit means utilization and the circulation systems therefor,

FIGURES 5 and 6 are perspective, part sectional views of part of the oven structure showing, respectively, two different arrangements for oven atmosphere extraction, FIG. 6 being a preferred form,

FIGURE 7 is a cross section of the oven structure as shown in FIGURE 6,

FIGURE 8 is an enlarged detail of part of the construction on a bank of radiant heating and forced convection heating conduit means and a modified form of forced convection delivery means,

FIGURE 9 is a diagram showing in greater detail the radiant heat circulation system shown in FIGURE 2, and

FIGURE 10 is a similar diagram to FIGURE 9 showing in greater detail the forced convection heating system shown in FIGURE 6 or 7.

In carrying the invention into effect according to certain preferred embodiments by way of example, there are provided above and below the path of articles (arrows 1, FIG. 1) through the baking chamber 2 of an oven, i.e. above and below the article conveyor means such as the oven band 3 (see FIGURES 7, 9 and 10 only), upper and

lower banks

4 and 5 of radiant heating conduit means or ducts R and forced convection heating conduit means or ducts C. Each

bank

4 or 5 is made up of

adjacent ducts

6 and 7 extending longitudinally of the baking chamber 2 and alternate ducts 6 and '7 are the radiant heating ducts R and the forced convection heating ducts C respectively. The radiant heat ducts R are imperforate and may be connected up at one end of each

bank

4 or 5 by a transverse header conduit 8 con nected to the outlet 9 from a radiant heat source It), and at the other end by a transverse header conduit 11 connected to the return side of the radiant heat source 10 through circulating means such as a fan 12 (see FIG- URES 2 and 9). The forced convection heat ducts C in each

bank

4 or 5 may be connected by a header 13 to the delivery of a fan 14 at one end (see FIGURES 4 and 10), the ducts C being blanked off at the other end. The forced convection heat ducts C are provided with means, such as orifices or perforations 16 (see, inter alia, FIGURES 2 to 4 and FIGURE 8) for the delivery of the 3 convection heat medium into the baking chamber 2 and onto the goods therein.

In a simple form of the above, see FIGURE 2, radiant heat ducts R alternate with forced convection heat ducts C across the Width of the baking chamber 2, oven atmosphere extraction being provided by suction conduit means or ducts S through orifices or perforations 15 spaced along the baking chamber, the ducts S being connected to the suction side of the fan 14 by trunking 14.

In a more complex utilization of the duct means 6 and 7 (see FIGURE 3) alternate radiant heat ducts R serve as forward and return paths R+ and R- for the radiant heating gas whereby the inlet and return headers 8 and 11' for the radiant heating gas are located at the same end of the

bank

4 or 5. Intermediate the forward and return radiant heat ducts R+ and R- are forced convection heat ducts C and additional suction ducts S or S may be provided in and along the

bank

4 or 5 having oven atmosphere extraction orifices 15 or 15'. Thus in FIGURE 3, the suction ducts S are located laterally on each side of the

bank

4 or 5 and have oven atmosphere extraction orifices 15 spaced therealong. In FIGURE 4, the suction ducts S comprise conduit means in the

bank

4 or 5 disposed between alternate forced convection heat delivery means C, the suction ducts S having oven atmosphere extraction orifices 15 spaced therealong.

The utilization of ducts across a section of a bank of ducts may alternate in repetitive sequence in the following examples:

(a) See FIGURE 2. Suction ducts S, radiant heat ducts R, forced convection heat ducts C, followed by alternation of ducts R and C across the

bank

4 or 5, the bank terminating in a second suction duct S,

(b) See FIGURE 3. Suction duct S, radiant heat forward duct R+, forced convection heat duct C, radiant heat return duct R, forced convection heat duct C, followed by alternation of ducts R-|-, C, R across the

bank

4 or 5, the bank terminating in a second suction duct S,

() See FIGURE 4. Radiant heat duct R, forced convection heat duct C, suction duct S, followed by alternation of the ducts R, C and S across the

bank

4 or 5.

In the case of the radiant heat duct R arranged as in FIGURE 2, the radiant heat gas may be supplied to the duct R at one end by the header 8 from the heater It), the other end of the duct R connecting with a return manifold in the form of a plenum chamber 11 (see FIGURES 1, 5, 6 or 7), which in the upper bank 4 is disposed above the forced convection heat duct C and in the lower bank is disposed below the forced convection heat duct C whereby the heating applied to the convection heating medium prior to discharge is increased.

A convenient construction of the bank of

ducts

4 or 5 as outlined above comprises wall members joined to one another at juxtaposed edges to form

closed ducts

6 and 7 of triangular, preferably equilaterial or isosceles, section extending longitudinally of the oven and arranged alternately with apices pointing in opposite directions so that the

triangular conduits

6 and 7 nest together, the base walls of alternate conduits being co-planar. In situ, these conduits 7 which present the base 7' of their triangular section to the articles in the oven chamber 2 (i.e., which face the oven band or the like) are the radiant heat ducts R and those conduits 6 which present the apices of their triangular section to the articles are forced convection heat ducts C (including, if required, oven atmosphere extraction ducts S as in FIGURE 4). Preferably the apical line (see especially FIGURE 8) of each triangular section forced convection heat conduit means C is a narrow flattened surface 17 parallel with the base (i.e. the section of each conduit means C is more properly a trapezium in that it is a triangle with its extreme apex removed) and the delivery orifice means 16 (or extraction orifice means are located along the flat surface 17. Thus in as assembled

bank

4 or 5 the narrow flat apical surfaces 17 of the forced convection heat ducts C lie between the relatively broad radiating surfaces 7 of the radiant heat ducts R.

Constructing the ducts of the

banks

4 and 5 in the manner referred to above results in a plurality of closed adjacent ducts spaced from the path along which articles are moved through the baking chamber, each of the ducts being formed by wall members that are supported within the chamber and joined to one another along juxtaposed edges. Between each adjacent duct is an imperforate wall that is common to itself and to the next adjacent duct. In alternate ducts, however, at least one of the walls thereof which is not common to the next adjacent duct is perforated to provide communication between itself and the baking chamber. The other ducts, however, have no perforated walls, thereby preventing communication between them and the baking chamber.

While a

conduit bank

4 or 5, as described above, may be made up by assembling the required number of

triangular section ducts

6 and 7 in alternately reversed relationship and securing them together, it is preferred to build up a

conduit bank

4 or 5 so that

adjacent ducts

6 and 7 share a common wall thereby simplifying construction, reducing Weight and materials and improving heat transfer between the radiant heat medium and the forced convection heat medium. To this end (see particularly FIGURE 8) a conduit bank is built up by securing between spaced parallel plates 18, constituting the top and bottom of the conduit bank, a plurality of spaced partitions provided by a plate 19 bent or corrugated into zigzag form to provide the apices and inclined common walls of the triangular section conduit means. The corrugated plate 19 has the apical lines of the corrugations on each side of the plate flattened, as mentioned above, and the plate 19 is secured to the top and bottom plates 18 of the conduit bank by, for example, welding the flattened apical lines 17 and 17' to the top and bottom plates 18. One of the plates 18 is then drilled through on the lines of the apical lines 17 of the corrugated plate 19 secured to it (and through the thickness of the corrugated plate along such lines) to provide orifices 16 for the delivery (or orifices 15'- FIGURE 4-for the extraction) of oven atmosphere to provide the forced convection heat and the portions of the drilled plate 18 lying between the lines of the rows of orifices 16 (or 16 and 15-FIGURE 4) constitute the radiating surfaces 7 of the radiant heat ducts.

In an alternative construction of an oven according to the present invention (see particularly FIGURES 5, 6, 7 and 8), the radiant heating means comprise, as before, radiant heat ducts R which extend longitudinally of the baking chamber 2 above and below the path of travel of the articles therethrough (eg, on an oven band 3). The forced convection heating means include, as before, ducts C extending longitudinally of the oven chamber and, in addition to the ducts C, convection heat delivery means ducts 20 extending transversely of the ducts C at spaced intervals along the length of the oven above and below the path of the articles therethrough. The transverse convection heat delivery means 20 therefor span the radiant heat ducts C and are interposed between the latter and the path of the articles through the oven chamber. Thus, the transverse convection heat delivery means 20 above the path extend downwardly towards the path from the level of the upper bank of radiant heat ducts R and the transverse convection heat delivery means 20 below the path extend upwardly towards the path from the lower bank of radiant heat ducts R. The convection heat delivery means 20 serve to receive the convection heat medium from the orifices 16 in the flattened apical surfaces 17 of the forced convection heat ducts C and to deliver the same in a distributed manner across the width of the oven chamber at spaced intervals therealong.

The transverse convection heat delivery means 20 are conveniently of elongated triangular (e.g. isosceles) section (e.g. as shown in FIGURE 8) disposed with the base against the radiant heat ducts R and the apex adjacent the path of articles through the oven chamber, e.g. adjacent the oven band.

The transverse convection heat ducts 20 may comprise complete conduit means, or the base of the triangular section of the ducts 20 may comprise the surface of the plate 18 of the conduit bank by securing thereto a V-section channel 21 (see FIGURE 6 or 7 for example) to provide the walls and apex of the transverse convection heat ducts. It is preferred to incorporate in the transverse convection heat ducts 20, as shown in FIG- URE 5, for example, transverse baflles 22 to localise the distribution from each of the orifices 16 in the forced convection heat ducts C.

Alternatively (see FIGURE 8), the transverse convection heat delivery means 20 may consist of a pair of spaced deflector plates 23 inclined inwardly towards one another so as to cause the heat medium delivered from the longitudinal convection heat ducts C to flow in the form of a vertical curtain, a restricting baflle consisting of a perforated strip 24 being provided between the deflector plates 23 to afford transverse distribution of the heat medium emerging from orifices 16 in the longitudinal convection heat ducts C.

While the extraction of oven atmosphere from the baking chamber 2 may be effected through laterally disposed orifices in lateral suction ducts S, as described above, transverse extraction means or ducts 25, similar to the transverse convection heat delivery means Ztl may be provided for extracting oven atmosphere from the baking chamber, see FIGURES l, 6 and 7, the extraction means 25 being located alternately with the transverse convection heat delivery means along the length of the oven and, preferably, so that the transverse convection heat delivery means 20 beneath the path of articles through the oven are vertically aligned with the transverse extraction means above that path, see FIGURE 7.

The forced convection heat systems described herein may be provided with adjustable damper means (not shown) in known manner to permit control of the forced convection heating either longitudinally or laterally of the baking chamber or both, and oven atmosphere recirculating plant such as suction and delivery fan means, auxiliary heating means, overspill conduits and the like are provided as necessary.

Dampers may be provided in the headers 13 connecting the convection heat ducts C with the discharge side of a fan 14 delivering oven atmosphere to the convection heat ducts C, each of which is in communication with the transverse convection heat delivery means 20 by means of orifices 16 provided in apices 17 of the ducts C. The transverse convection heat delivery means 20 are themselves divided into separate chambers by the baflles 22 into which convected heat medium enters by way of the orifices 16 and finally discharges therefrom into the baking chamber 2 by way of the outlet means along the length of the delivery means 20. Manipulation of the dampers controls the amount and location of forced convection heat medium entering the baking chamber, e.g. as a complete curtain extending transversely of the chamber or in selected separate widths governed by the baffles 22.

An oven of preferred construction may have the structure of the radiant and convection heating ducts extending on either side of the radiant heat source, for example, in the form of a burner and its associated flame tube. Depending upon the total length of the oven, so a number of these assemblies would be used, each being spaced apart longitudinally of the oven to allow for expansion and to permit access to the oven for such purposes as inspection and lighting.

Furthermore the structure of the radiant and convection heating ducts may extend from only one side of the radiant heat source and thereafter extend from either side as above described. From the foregoing it will be obvious that an oven can be constructed from any combination of the above structures.

The radiant heating means may comprise any convenient type such as directly or indirectly heated fluid (gas or liquid) or heating elements (e.g. electric) disposed within the radiant heat ducts themselves.

I claim:

1. An oven comprising a baking chamber containing a movable conveyor defining a path along which articles may be moved through said chamber; a pair of spaced apart plates supported in said chamber and spaced from said path; a plurality of spaced partitions interposed between said plates and forming with the latter a plurality of adjacent ducts each of which has a Wall that is common to itself and to the next adjacent duct, certain of said ducts being perforated and in communication with said chamber, the remainder of said ducts being imperforate; and means in communication with each of said ducts for introducing a heating medium thereto.

2. The construction set forth in claim 1 wherein said partitions are constituted by a sheet member shaped to substantially zig-zag form.

3. The construction set forth in claim 1 including header means interconnecting opposite ends of said imperforate ducts for circulating said heating medium therethrough.

4. The construction set forth in claim 1 including first header means connecting selected perforated ducts; second header means connecting selected other perforated ducts; and blower means having its discharge side connected to said first header means and its suction side connected to said second header means.

5. The construction set forth in claim 1 wherein said partitions extend longitudinally of said chamber.

6. An oven having a baking chamber containing a movable conveyor defining a path along which articles may be moved through said chamber; a first bank of adjacent, parallel ducts supported in said chamber below said path, each of said ducts having a wall common to itself and to the next adjacent duct; a second bank of ducts similar to the first bank of ducts and supported in said chamber above said path, certain ducts of said first and second bank of ducts being perforated and in communication with said chamber, the remaining ducts of said first and second bank of ducts being imperforate; and means in communication with the ducts of said first and second bank of ducts for introducing a heating medium thereto.

7. The construction set forth in claim 6 including additional ducts disposed transversely of the ducts of said first and second bank of ducts and being in communication with said perforated ducts, said additional ducts also being perforated to communicate with said chamber.

8. An oven comprising a baking chamber containing a movable conveyor defining a path along which articles may be moved through said chamber; wall members supported within said chamber and joining one another along juxtaposed edges to form a plurality of closed, adjacent ducts spaced from said path, each of said ducts having an imperforate wall member that is common to itself and to the next adjacent duct; and means in communication with each of said ducts for supplying a heating medium thereto, at least one remaining wall member of each of a selected number of said ducts being perforated to provide communication with said chamber, the remaining wall members of the other ducts being imperforate to prevent communication between said other ducts and said chamber.

9. The construction set forth in claim 8 including other wall members forming suction conduit means supported in said chamber, said other Wall members having openings therein in communication With said chamher; and suction means communicating with said suction conduit means for introducing oven atmosphere into said suction conduit means from said chamber.

10. The construction set forth in claim 9 including header means interconnecting said suction conduit means and the ducts of said selected number of ducts for recirculating oven atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS Hormel Mar. 12, 1935 Warrington July 22, 1952 Warrington Mar. 15, 1955 Frenger Sept. 20, 1955