Open Top Compact Dryer Oven for a Web

The invention relates to an improved dryer oven for a textile web and other sheet-like material which is constructed for higher efficiency and cleanability.

In the textile industry, it is common to dry a traveling textile web by passing it through a dryer oven on tenter chains. Other industries also use ovens for drying sheet-like material which travels through the oven. Normally, the ovens are quite large and require that an attendant enter the oven in order for it to be cleaned of waste, dust, and other contaminant particulate matter. In the case of drying fabrics containing volatiles, the residual condensed vapors must often be cleaned from the oven parts, burners, etc. The interior of the typical dryer oven has been constructed as a large box, for example, see U.S. Pat. No. 4,295,284. An average housing for a textile tenter oven is 90 feet in length, 15 feet in width, and 7 feet in height. The oven also includes up to three penthouses on top which house burners, etc., each penthouse is about 10 feet in length, 15 feet in width, and 8 feet in height. The oven housing is not compact and the attendant must enter the large and dark housing in order to clean the parts. The large size and thermal mass in oven structure normally do not allow for the oven to cool down in time for cleaning. Because of the nature of the cleaning operation and the necessity of entering the large housing box, the oven is not cleaned or the attendant often does not perform a thorough job because the oven is still hot or warm, reducing the efficiency and life of the oven. If volatile ovens are not cleaned properly, they can quite easily catch on fire resulting in damage and danger. Explosions quite often result in oven damage. The drying efficiency of the prior art heater ovens is a problem to which little attention has been given. Attention has been somewhat diverted from the problems of cleanability and efficiency and drawn instead to the other mechanical aspects associated with conveying the fabric through the large housing box while contacting opposing sides of the web or sheet material with hot air.

Typically, the textile web drying ovens have consisted of one large housing in which two superposed dryer units are arranged between which the web travels. A plurality of spaced hot air ducts normally are used across the dryer units transverse to the direction of web travel as shown in U.S. Pat. No. 3,739,491. Once the hot air leaves the ducts, it impinges upon the top and bottom of the web. Air control in this area is crucial to the dryer efficiency and performance. Uniform drying of each side of the web is critical. If drying is uneven, streaking or shading of dyed fabrics may result through wicking of the dye. In the case of coated fabrics like latex coated furniture fabrics, the coating will overcure in some areas while undercure in other areas when the drying rate is not uniform. After the fabric is converted to furniture, fabric shading occurs in the areas of overcuring resulting in customer complaints and returned furniture.

Due to the fact that there are many different types of fabric which now need to be dried on the same dryer, many dryers are being made with variable speed blowers to accommodate the different fabrics on the same dryer. However, the existing single nozzle type of air distribution system is still being used in combination with the variable speed blower. The result is the development of eddy currents at certain speeds which result in unbalanced air distribution and uneven drying.

Various structures and methods are used to impinge the hot air upon the traveling web. The single nozzle distribution system is typical of that shown in U.S. Pat. Nos. 4,516,332 and 4,523,391. U.S. Pat. No. 2,144,919 discloses an arrangement of a web drying oven wherein hot air is distributed between transverse ducts, rather than through the ducts as in U.S. Pat. No. 3,739,491. In the '919 patent, the ducts return the air after contacting the traveling web. The ducts are contoured to provide special air flow treatment of the air passing between the ducts to contact the web. In particular, the ducts are shaped to define nozzles which deliver the jets of hot air against the web at angles from 20-30 degrees. U.S. Pat. No. 3,678,599 discloses particular arrangements of air ducts with a perforated concave rib between adjacent ducts. This arrangement is said to stabilize the web moving longitudinally. In this arrangement, the transverse ducts are used for the return of air rather than distribution of hot air. Slot shaped openings are defined at the ends of the rib which direct the hot air in opposite directions. The ducts are said to consist of airfoil sections. The selection of the cross-section of the perforations in the ducts and the vacuum inside the ducts is said to control desired flow conditions. However, this results in a relatively theoretical and complicated determination of air flow characteristics which may not be susceptible of exact determination or practical embodiment. There is also a space between adjacent pairs of ducts in which there is no flow treatment. U.S. Pat. No. 3,060,594 discloses an apparatus for drying webs with hot air or other medium in which provision of a desired air flow pattern is sought to accomplish contact-free and tension-free guiding and drying of webs freely floating within a treatment chamber. In this case, air is discharged from transversely extending ducts and is returned between the ducts.

Various arrangements have been provided for forcing the hot air into the dryer sections. Dual blowers are shown in U.S. Pat. No. 4,137,649 and a single blower is shown in U.S. Pat. No. 4,516,332. Typically, these blowers deliver the air through trapezoidal shaped boxes as illustrated in the aforesaid patents. The air may be heated by a burner or conventional means and taken in by the intake side of the blower. The hot air taken in may also be mixed with the return air from the dryer sections as illustrated in the '332 patent. A single source of heat may be used such as in U.S. Pat. No. 4,551,928, or plural sources of heat may be used such as shown in the '649 patent, one each for the two blowers.

Accordingly, an important object of the invention is to provide a compact dryer oven for a web and the like material which provides balanced hot air distribution for even drying of the web.

Another object of the invention is to provide a web drying oven which is compact and easily cleanable.

Another object is to provide a compact web drying oven having a minimum interior volume so that accumulations of volatile vapors is reduced and a releasable upper housing that will open should an explosion occur to reduce dryer damage.

Another object of the present invention is to provide a dryer oven for a web and like sheet material which is compact and has an upper pivotal housing which may be opened for access to clean the oven without the need of entering the dryer box.

Another object of the invention is to provide a dryer oven for a web and the like material having improved hot air flow distribution for more efficient drying and support of the web traveling through the treatment section of the oven.

Another object of the invention is to provide a dryer oven for a web and the like material which is compact and has a closed circuit air distribution system with a short path which eliminates the use of long supply ducts and increases the number of air changes per minute to provide more efficient and protective use of blower horsepower and a lower temperature differential between supply air and return air, all of which enhances the efficiency of the oven.

Another object of the invention is to provide a dryer oven for a web and the like material having a hot air distribution system which uses a plurality of separate nozzle orifices which balance the air distribution and provide a combination tangential and center lift air flow relative to the traveling web which accelerates drying rates without using high air forces that would tend to push down the pile of pile fabrics and push in the chemical compounds of coated fabrics.

Another object of the invention is to provide a compact dryer oven for a web and the like material in which the interior space and material used within the interior of the oven are both reduced which allows reduced heat mass inside the oven to provide for extremely fast start-up times and low energy consumption.

A compact dryer oven is disclosed for a traveling web and the like which may be easily cleaned without entering the oven and which is reduced in interior space and structure for more efficient drying. The oven comprises a lower fixed housing and an upper pivotal housing which may be opened to expose both housings for cleaning without entry. The oven has a compact volume to reduce build up of explosive vapors and the upper housing releases in a pivotal action in the event of an explosion. The web travels between the lower and upper housings. Advantageously, each housing includes an identical hot air distribution system so the web is dried evenly on both sides. Each housing includes a hot air discharge device carried in the housing for discharging hot air into the housing. An air diffuser manifold is carried in the housing which extends longitudinally in the direction of web travel. The diffuser manifold receives the discharged hot air and distributes the air radially in equal parts across the width of the web. The air diffuser manifold is carried centrally in an upper part of an air equalizing chamber in the housings which receives the proportioned air flows. A hot air register is carried below the diffuser manifold means across a lower part of the air equalizing chamber. The hot air register includes a plurality of longitudinally spaced tubular members extending laterally across the diffuser manifold and spaced longitudinally in the direction of web travel. An air dividing nozzle is carried between adjacent tubular members for splitting the hot air passing between adjacent tubular members into a first air flow and a second air flow, generally tangential to the web and in opposite directions. The air flows are returned, after traveling a short path, through the tubular members. The air dividing nozzle includes a divider body, and a first nozzle opening between adjacent tubular members upstream of the divider body. There is a second nozzle opening between the divider body and the adjacent tubular members having an area less than the area of the first nozzle opening so that the hot air increases in velocity as it passes through the second nozzle. An expansion zone follows the second nozzle opening having an area greater than the second nozzle to decrease the velocity of the hot air. A third nozzle is created between the divider body and the adjacent tubular members below the expansion zone which has an area less than the area of the expansion zone to increase the velocity of hot air. The series of increasing, decreasing and increasing velocities and pressure of the hot air balances the distribution of hot air delivered through the lower and upper hot air registers so that the web is evenly dried. The tubular members include an air return slot extending longitudinally along the length of the tubular members facing the web for return of air from the first and second air flows. One end of the tubular members is connected to an intake of a heater which supplies heated air to the air discharge device.

Uniform and tangential air flow provides accelerated drying rates for surface sensitive fabrics. The two direction air flow pattern provides a center vacuum which has a lifting action to pile type fabrics. One air jet blows left to right and another air jet blows right to left. Therefore, there is no tendency to force fabric pile in a fixed direction. The air flow also provides advantages to fabrics which have been coated with latex rubber or some other form of chemical compound, the combination tangential flow with center left allows accelerated drying rates without using high air force which would have a tendency to push the chemical compounds into the fabric. Extremely uniform air flow by use of separate nozzle orifices level and balance air distribution on the web. Slotted air return orifices move air from the nozzle air jets directly to the return air tubes in the direction parallel with fabric direction. A special hinged upper housing allows the whole dryer upper section to be lifted to facilitate cleaning and maintenance without requiring operators to enter a dark, usually hot enclosure, thereby reducing the clean-up time. A short circuit air system allows for an extremely reduced air supply and return path without the use of long supply ducts, thereby increasing the number of air changes per minute providing more effective use of fan horsepower and a lower temperature differential between supply air and return air. Elimination of space consuming ducting allows reduced heat mass, thereby providing extremely fast start-up and low energy consumption.

The construction designed to carry out the invention will hereinafter be described, together with other features thereof. The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings forming a part thereof, wherein an example of the invention is shown and wherein:

FIG. 1 is a front elevation illustrating a series of dryer ovens constructed in accordance with the invention arranged side by side for drying a continuous web traveling through the ovens;

FIG. 2 is a perspective view of a compact dryer oven constructed in accordance with the present invention having a pivotal upper housing;

FIG. 3 is a sectional view taken along line 3--3 of FIG. 1;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3 illustrating the air divider assembly of the present invention;

FIG. 5 is a sectional view taken along line 5--5 of FIG. 1;

FIG. 6 is a partial section showing another embodiment of an air heater in accordance with the invention;

FIG. 7 is a front elevation of a web dryer oven having a fixed lower housing and pivotal upper housing according to the invention; and

FIG. 8 is a top plan view of the web dryer oven of FIG. 7.

Referring now in more detail to the drawings, a compact dryer oven is illustrated, designated generally as A, for drying a traveling web W and other sheet-like material which may be easily cleaned without entering the oven and is reduced in interior space and structure for more efficient drying and safety. As can best be seen in FIG. 1, one or more ovens A may be arranged in tandem, four in FIG. 1, for drying the web. The number of ovens used depends on the application being made. It has been found according to the invention that twice the drying may be had with the tandem arrangement as compared to the prior textile ovens having equivalent floor space. In the illustrated application, web W passes through a coater 11a, the series of dryer ovens A, and a cooler 11b, to a winder 11c where the web is taken up on a roll 11d. As can best be seen in FIG. 7, the oven comprises a fixed lower oven housing B and a movable upper oven housing C disposed above the lower oven housing. Pivot support means D is provided for pivotally carrying upper oven housing C above lower oven housing B between a closed position (FIG. 3) in which web W travels between the housings for drying, and an open position (FIG. 2) in which housing C is raised and access can be had to an interior, designated generally as 10, of the lower and upper oven housings for cleaning of the interiors. Lower and upper oven housings, B and C, consist of lower and upper housing enclosures 12B and 12C having lower and upper housing openings, designated generally as B, 14B and 14C (FIG. 3). Lower housing opening 14B faces upper housing opening 14C and web W travels across the lower and upper housing openings through the oven. A lower hot air register E is carried generally co-extending across lower housing opening 14B and upper hot air register F is carried generally co-extending across upper housing opening 14C from which hot air, shown by arrows 16, is delivered for contacting and drying lower side 20B and upper side 20C of web W, respectively.

As can best be seen in FIGS. 3 and 4, each lower and upper hot air register E,F includes a plurality of tubular members 22 carried across lower and upper housing openings 14C and 14B spaced longitudinally in the direction of web travel. Tubular members 22 are used to return air which will be explained later. Air dividing nozzle means G is carried between adjacent tubular members 22, i.e. 22a and 22b, for splitting hot air 16 passing between the adjacent tubular members into a first air flow 26 and a second air flow 28 generally tangential to web W and in opposite directions. Air dividing nozzle means G includes a divider body 30 having a nose 30a which splits the hot air flow in half. There is a first nozzle opening 32 between the adjacent tubular members upstream of divider body 30. A second nozzle, designated generally as 34, defined between divider body 30 at a convex part 36 and adjacent tubular members 22a, 22b having an area less than the area of first nozzle opening 32 so that the hot air increases in velocity passing through nozzle 34. An expansion zone 38 follows second nozzle opening 34 between a concave portion 39 and adjacent tubular members having an area greater than second nozzle 34 to decrease the velocity of the hot air. A third nozzle, designated generally as 40, is defined between said divider body 30 at a convex part 42 and adjacent tubular members 22a, 22b having an area less than the area of expansion zone 38 to increase again the velocity of the hot air flow. The series of increasing, decreasing and increasing changes in velocity and pressure of the hot air passing through second nozzle 34, expansion zone 38, and third nozzle 40 levels and balance the distribution of hot air delivered through lower and upper hot air registers E and F so that web W is evenly dried. The unique design of the double nozzle 34, 40 air flow system yields a highly leveled air distribution without significant resistance, resulting in high efficiency. This unique design also offers the advantage of automatic nozzle cleaning of the orifices due to the resultant pressure changes which tend to blow out accumulated lint.

Reference will now be had to the entrance of drying air into lower and upper housings B and C. Since the air distribution system is identical for each housing, reference will be made only to upper housing C for purposes of explanation. As can best be seen in FIG. 3, each housing includes hot air discharge means H for discharging hot air into the housing. A reducing plenum means I receives hot air and reduces the air into a generally steady horizontal air flow 42. Air redirecting means J receives the horizontal air flow 42 and directs the horizontal air flow into a generally vertical air flow 44. A diffuser manifold means, designated generally as K, receives the vertical air flow 44 for separating and proportioning the air flow into generally equal parts and directing proportioned air flow 45 into an equalizing chamber 46, i.e. lower and upper equalizing air chambers 46B and 46C, respectively.

Diffuser manifold K distributes a plurality of equal air flows 45 radially across the width of chambers 46B and 46C so that hot air is supplied evenly across the width of web W passing between lower and upper air registers E and F. Means for splitting the proportion air flows 45 includes tubular members 22 and air divider nozzles G spaced across the enclosure openings 14B, 14C, which are the openings of equalizing chambers 46B and 46C, for receiving proportioned air flows 45 and dividing the air flow into first air flows 26 in the direction of web travel and second air flows 28 opposite to the direction of web travel. Uniform and tangential air flow provides accelerated drying rates for surface sensitive fabrics. The two direction air flow pattern provides a center vacuum which has a lifting action to pile type fabrics. Since one air jet blows left to right and another air jet blows right to left, there is no tendency to force fabric pile on a fixed direction. The air flow also provides advantages to fabrics which have been coated with latex rubber or some other form of chemical compound. The combination tangential flow with center lift at 48 allows accelerated drying rates without using high air force which would have a tendency to push the chemical compounds into the fabric.

It has been noted that air equalizing chambers 46B and 46C are carried in lower and upper housing enclosures 14B and 14C surrounding and enclosing lower and upper hot air registers E and F. Longitudinal air return slots 50 are formed along the length of tubular members 22 through which first and second air flows 26 and 28 are exhausted. Tubular members 22 are preferably round and first nozzle 32 is formed by circumferential converging walls 52 of tubular members 22.

As can best be seen in FIGS. 2 and 3, each oven housing enclosure 12B, 12C includes a first (front) end wall 54 at which web W enters said oven, a second remote end wall 56 from which the web exits said oven, a back wall 58 integral with the first and second end walls, a top wall 59 integral with the back wall and the end walls which includes an inclined portion 59a, and a front wall 60 integral with the top wall and end walls. A frame, designated generally as M, includes legs 61a, front end rails 61b and 61c, and side rails 61d which support housings B and C in a manner which will be more fully explained later.

Air discharge means H includes a pair of first blowers 62 carried in lower housing B and a pair of second blowers 63 carried in upper housing C, and heater means 64 for supplying heated air to each of the blowers 62, 63 for discharge in respective ones of the housings. The blowers are driven by respective electric motors 62a,63a carried on the housings. Heater means 64 includes a gas burner 65 for heating air and a first heater duct 66 extending into lower housing B between blowers 60 for supplying heated air to the first blowers 60. A second heater duct 68 extends through lower housing B into said upper housing C for delivering heated air to said second blowers 62. First and second heat ducts 66 and 68 are concentric. Second duct 68 is carried within first duct 66 extending through lower housing C into upper housing B exactly between blowers 62. Ducts 66,68 terminate in perforated sections 66b,68b for distributing air centrally to the blowers. Butterfly valves 66a and 68a proportion the air flow so it may be equalized to blowers 62, 63, respectively. An efficient end seal system is provided by a flexible brush assembly 69, FIGS. 4 and 5, wherein channel brushes 69a are carried by end rails 61b at each dryer end 56 and 54 of the end dryers A in the series. The brushes may be carried at the entrance and exits of the end units only, or in the case of one oven, at each end 54, 56. The brushes are constructed of fine gauge wire of stainless steel, brass, or other non-melt materials. Brushes are fitted to meet at the web line. Tenter rails 70 displace brush fibers to form a tight seal around the rail profile. Deflectors 70a deflect brush filaments around pin bars 70b (or clips on clip tenter) to prevent wear from the pin movement. The web is attached in a conventional manner to pin bars 70b. The brushes retain the hot air in the housing.

Diffuser manifold means K includes a radial assembly of elongated cylindrical pipes 71 disposed centrally of equalizing chamber 46 extending longitudinally in the direction of web travel over the length of housing C. The pipes are radially arranged and spaced apart to define radially spaced longitudinally extending slot openings 72 between adjacent pipes through which air is distributed and proportioned equally for equalized distribution across the width of web W. The pipes are preferably hollow pipes having round cross sections. The air return system includes an exhaust blower 74 connected to a blower return duct 76B to which ends 22C of tubes 22 are open and in fluid communication for the return of air. Upper return duct 76C returns air from upper tubes 22 via lower return duct 76B. Return air 77 then goes through duct 78 to exhaust blower 74 and then to burner 65. A diverting valve 79 may be provided to exhaust some return air to ambient rather than recycle. As can best be seen in FIG. 4, air is also drawn off the ends 54,56 through hollow perforated rail 61b attached to suitable suction.

Referring to FIG. 3, redirecting means J includes inclined wall 80, straight wall 82 and a curved wall 84 merging into a curvature of the radially arranged pipes 71 for redirecting air flow vertically through said radial slot openings 72. It is noted that cylindrical diffusers 71 are in a direction parallel to fabric travel. Air then flows from equalizing chamber 46 to nozzles 32 as shown in FIG. 4. The conical surfaces 52 induce the effect of shaping the air flow into a smooth and laminar condition. In the drying and evaporation process with moving web W, a thin air/moisture layer 86 (FIG. 4) travels with the web. Layer 86 substantially inhibits continual heat transfer to the web and further vapor removal by effectig a seal over the web. This layer is broken up by employing air stream 28 tangential to the web which lifts layer 86 and directs it to the vacuum created at slot 50. Secondly, air movement forms a vortex between tubes 22 and nozzle G generally at 87 creating a vacuum. This vacuum helps remove layer 86 and direct it to slot 50. The vacuum also helps to pull vapors within the web to the surface.

The specially shaped nozzle divider G serves to split the air flow into equal streams 26 and 28, which are in opposite direction to each other and due to the curved surface of the return air tubes 22, the discharging air is forced in a direction downward and tangent to the fabric flow which provides both the drying air and, in the case of the lower air system, a support air system. Slots 50 in return air tubes 22 capture this air at the approximate center of the tubes. This provides for a short discharge--drying period after which the hot air is sucked into the tubes 22. Return air tubes 22 are positioned with one end open to the negative pressure of the fan intake.

As can best be seen in FIG. 6, heat may also be applied to the discharge air by electric or steam coils 86 (commercially available) carried by the housings on the discharge sides of blowers 62, 63. Air passing over the hot coils induces heat to the discharge of the blowers and is discharged to the web.

The releasable, pivotal opening of upper housing C, and the mounting of the housings on the frame M will now be described in reference to FIGS. 2, 5 and 7. An L-shaped flange 90 is carried by each end 54,56 of housing C which rests on end rails 61b when upper housing C is closed. It is noted that a sealing strip 93 of suitable heat resistant material extends along the joint of front walls 60 of the lower and upper housings when closed to seal against heat loss. Pivot means D includes a pivot arm 92 affixed to housing C and pivotally attached by pivot pin 94 to lower housing B. Lower housing B is affixed to frame M in any suitable manner such as welding, in an under slung manner. It can be seen then that the interior of housings B and C is greatly reduced in its volume compared to the prior textile dryer and the like ovens. This minimized volume has less tendency for an explosion since the amount of volatile vapors is reduced. However, in the event of an explosion, upper housing will release from its closed position and pivot upwards if sufficient pressure exists to relieve the effects of the explosion and minimize damage to the oven. For this reason, upper housing is provided with a release means N in connected between the housing and frame M which yields to pressure allowing housing C to pivot upwards. Release means N includes a leaf spring 96 having one end 96a pivotally attached to end rail 61b at a pivot 98. A medial portion 96b of the spring slides on a rider 100 affixed to end rail 61b. A free end 96c is received in a retainer 102 carried by end 54 of housing C. Spring 96 applies a biasing force which assists in the release and raising of the housing requiring only about 50 lbs force to open the housing. Thus, the housing will release and pivot open before the forces of an explosion will damage the interior parts of the oven.

Thus, it can be seen that a highly advantageous construction can be had according to the invention for evenly drying a web and facilitating oven cleaning. Extremely uniform air flow is achieved by use of three separate nozzle orifices 32, 38, and 40 which balance air distribution to web W. Air return slots move air from the nozzle air jets directly to return air tubes in the direction parallel with fabric direction. Prior machines used an open channel whereby the air moved perpendicular to fabric travel, this provides that as the air picked up moisture, it cooled rapidly and was traversed across the fabric, subjecting the edges to a different drying condition than was at the center. Single side mounted fans with central air supply provide the advantage of saving space within the dryer enclosure, the center distributor assures that this air is uniformly distributed to each dryer side. Previous single side designs feed air distribution to only one side. A special hinged housing assembly allows the whole dryer upper housing to be lifted to facilitate cleaning and maintenance without requiring operators to enter a dark, usually hot enclosure, reducing the clean-up time. A short path air system allows for an extremely reduced air supply and return path without the use of long supply ducts, thereby increasing the number of air changes per minute providing more effective use of fan horsepower and a lower temperature differential between supply air and return air. Reduced internal material, i.e., elimination of space consuming ducting, allows reduced heat mass, thereby providing extremely fast start-up and low energy consumption.

While a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.