US2831267A - Drying apparatus - Google Patents

Description

April 22, 1958 P, J, GARDNER 2,831,267

DRYING APPARATUS Filed Deo. 29. 1954 s sheets-sheet 1 IN VEN TOR.

PAUL JQ GARDNER Arrows/EY pil 22, 1958 V P. J. GARDNER 2,831,267

DRYING APPARATUS Filed Dec. 29. 1954 5 Sheets-Sheet 2 (f) Q' 1 u- IN V EN TOR.

PAUL J, GARDNER BY April 22, 1958 P.'.I.'GAR|:J|\1ERv 2,831,267

DRYING APPARATUS Filed Deo. 29, 1954 3 Sheets-Sheet 5 FIG. 7

FIG. 6

IN VEN TOR.

PAUL J. GARDNER DRYHG APPARATUS Paul l. Gardner, Davenport, Iowa, assgnor to Bendix Aviation Corporation, Teterboro, Nfl., a corporation ,of Delaware Application December 29, 1954, Serial No. 47 8,313

Claims. (Cl. SLS-60) This invention relates to drying apparatus, and is especially directed to a drier of the type which combines the action of radiant heat with that of an air current.

In production operations requiring the drying of articles, it is important to carry out the drying step as rapidly as is consistent with adequate and eiiicient drying, since a shorter drying time means greater production per machine and lower costs. This is especially important in drying articles such as machine parts after cleaning or other liquid treatment, since the shape of such parts often increases the difficulty of removing all of the liquid from recesses and interstices. It has been found that with prior types of driers this operation has been comparatively lengthy and correspondingly expensive.

Rapid drying is also important where the retention of liquid on the article surface may have objectionable effects, such as staining or other discoloration or the formation of surface films, which make it desirable to remove the liquid as promptly as is practical.

An object of the invention is to provide a drier that will substantially reduce the time required for efficient drying of articles, and particularly of apparatus parts and the like having irregular contours.

Another object is to combine radiant heat with an air current in a novel manner that increases the eiiiciency of the drying apparatus.

A further object is to provied an improved air drier in which higher air velocity in the dryingzone is obtainable; and a related object is to arrange the drierso that the high speed air ilow is uniformly distributed through said drying zone.

An object is to-provide an arrangement for returning air in the drying chamber but outside of the drying zone, and especially air that is heated, to the .supply of drying air directed to such zone. A related object is to provide an ancillary current of cooling air around a radiant heat source.

A further purpose is to provide a`drier that is eflicient,

compact, readily constructed and operated, and which utilizes standard units.

The foregoing and other objects and advantages of the invention will appear more fully from consideration of the detailed description which follows, together with the accompanying drawings wherein two embodiments of the invention are illustrated. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description and are` not to be construed as defining the limits of the invention.

ln the drawings:

Fig. 1 is a vertical central section on line 1-1 of Fig. 3, with part of the blower broken away, illustrating one embodiment of the invention;

Fig. 2 is a front elevation of said embodiment with part of the blower broken away;

Fig. 3 is a plan view thereof;

Fig. 4 is a similar plan view of amodied .embodiment;

nited States Patent chamber 11.

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Fig. 5 is a wiringdiagrarn; Fig. `6 is a vertical central section through another modied form, the lower portion being broken away;

.and

Fig. 7 is a horizontalsection on line 7-7 of Fig. 6.

The drier includes .avhousing l10 enclosing a drying chamber 11. In theform illustrated, the housing is rectangular and includes .a front wall 12, side walls 13, rear wall 14, top 1S and ybottom 16, all formed of sheet metal marginally connected and mountedon an .angle iron framev 17 to form aclosed chamber. The lower portion ,of the frontwall 12` is formedbya hinged 'door 18 havarticles to be dried, located below the AoutlettZS of tubek 21. As illustrated, this comprises angle supports 26 mounted on frame 17an'd `racks 27l removably carried ,by said supports, on which' articles to be dried are placed. Such articles may conveniently be arranged in an open mesh basket28 located below the tube outlet 25. The region in which articlesv 4on racks'27 will be located constitutes a drying zone. v v

An arrangement ishprovided for assuring the uniform distribution of the air llow over `racks'27 in the drying zone, this arrangementincluding an outlet located below said racks and formed by a relatively narrow slot arrangement extending'circumferentially through the wallsof the housing k10 adjacent'to the bottom. In the form 'illustrated, the `airoutlet slot '29 extends through said Walls entirely around the vhousing immediately above the bottom, aportion of the slot being located below door,1'8 as shown in Fig. 2. With this arrangement the air from tube outletlZS travelsdownwardly and outwardly with uniform outward Aspread to slot 29, asindicated. A lilter or air diffuser 52 of ftibrousmaterial offering a minimum of air'resistance-maybe mounted on the chamber walls just above the slot Y29, extending entirely .across the chamber.

An arrangement'for'heating 'the air passing through ltube 21-is advantageouslyprovided,and ,may conveniently include'an electrical heating element 30 mounted Ain the discharge -pipe 23 of blower 22.

Means for :directing radiant heat against the .articles mounted on racksZZ is provided in the upperpart of Invthe form illustrated, said means includes a pluralityl of electrical heat radiating .lamps 31 of conventionalform, including internal reflectors, detachably mounted in'standard` receptacles 32 fixed to the housing top 15 and symmetrically'arrangedaround tube 21 in corner portions of chamber 11. .The lamps '31 are advantageously located and oriented in properpositions to apply-radiantheat-with relative uniformity over the entire surfaceof racks 27. QThevtube outlet 25' is advantageously located no higher than vthe lower ends of `locationat the top of, the-.chamber andclose to said lamps.

An arrangement-is provided .for feedingsuchair from Ptented Apr. 22, 1958 Vestablish the appropriate output velocity,

the top of chamber 11 into tube 21, thereby avoiding the accumulation of heated air, cooling the upper part of said chamber which normally contains or is adjacent to electrical wiring and parts that might be affected by excessive heat, and utilizing the heat in said air to assist the drying operation.

For this purpose the inner face of tube 21 converges slightly from both ends to a thickened zone 33 located adjacent to the upper end of the chamber 11 and forming a venturi throat. Air passages 34 extend from said throat outwardly through tube 21 into communication with the upper part of chamber 28. The suction effect of the air flow through throat 33 will draw air inwardly into said stream in tube 21 through passages 34, which are circum- Vferentially distributed to produce even withdrawal of the air from the upper part of chamber 11.

With this arrangement an exceptionally large volume of air at relatively` high velocity can be passed around and through the articles to be dried, which are located in the direct path of the expanding air stream. Heat is uniformly applied, not only from the heated air itself but also from the lamp radiation, which is immediately eifective when the apparatus is turned on. The radiant heating arrangement is moreover eticient because its heat is concentrated in the area where it is required. Further, this heating system is advantageous compared to air heating arrangements, since it can be placed in and out of operation immediately merely by operating a suitable switch 35 (Fig. 2) which controls the lamps 31, instead of waiting for the air to be heated. A separate switch 36 for the blower 22, and a switch 37 for the blower air heater 30, permit iiexible operation of the system, which can dry with cold air, heated air, or radiant heat alone or in combination with either type of air, by manipulating said switches, a suitable circuit across power line 38 is shown in Fig. k and independent operation as described may be obtained by using the alternative circuit indicated by dotted line 39. In general, however, the full line circuit is preferred, with the lamp circuit connected at one side to the blower circuit beyond switch 36, so that the heat lamps 31 cannot be turned on unless the blower is operating.

The requisite air velocity in the drying zone is obtained by providing the necessary input velocity through tube 21, by proportioning the total area of outlet slot 29 to and by arranging housing to close chamber 11 except at tube 21 and slot 29. In a practical embodiment of the invention an input velocity of 2,000 feet per minute and an output velocity of 450 feet per minute were maintained, producing an air velocity throughout the drying zone very much higher than was found to be practicablewith previous dryers. The arrangement provided an air ow of hfty cubic feet per minute. This exceptionally high velocity and volume of air not only dries articles much more rapidly and etliciently, but also makes it possible to dry readily articles that are intricate in contour, which were diicult or impossible to dry in previous driers, the high velocity of the air reaching and removing moisture from remote recesses which could not be penetrated by air streams at lower velocities.

The arrangement also facilitates the use of more than one air source if desired, a modification using two blowers and air supply tubes being illustrated in Fig. 4. In this arrangement the tubes 21a are located symmetrically at opposite sides between pairs of heat lamps 31. In this way a greater volume of air at high velocity, and the distribution of air at such Velocity over a wider area, can be obtained. However, it will be evident that the construction is such that it is not restricted to the use of only two air supply units, or to the use of only four heat lamps.

In the embodiment illustrated in Figs. 6 and 7, another arrangement for recirculating the heated and a lter for the incoming air, are provided. In this arrangement a top casing 40 having continuous side walls 41 fixed to and extending upwardly from housing 10, has a top opening 42, and carries an air filter extending across said opening, the form illustrated including a hat electrostatic lter 43 covering the entire opening and supported on rails 44. A bathe plate 45 extending across casing 40 has a central air supply opening 46 concentric with air supply tube 21A mounted on housing top 15A.

An electric fan 47 has a motor 48 mounted on support bars 49 xed to baille plate 4S and extending across opening 46, with the fan blades 50 spaced from the motor and located in the upper end of air supply tube 21A. Heater 30A is mounted in tube 21A below fan blades 50. As illustrated, tube 21A may extend above top 15A, and theair outlet 25A at its lower end may be higher than the lower ends of heat lamps 31; but while these features have advantages, they are not intended to be restrictive.

Housing top 15A is provided with openings 51 spaced around tube 21A, arranged to provide adequate upward `ow of air from the upper part of housing 1t) to prevent accumulation of hotvair in that region, the fan-created suction at the top of tube 21A serving to maintain the requisite air ow through openings S1. While two openings 51, underlying the edge of baille opening 46 and evenly spaced between opposite pairs of lamps 31, are disclosed, the desired result may be obtained with other arrangements. The lower part of this embodiment is the same as that shown in Figs. 1 and 2.

In the operation of this embodiment the air is drawn through filter 43, so that not even line particles of airborne dirt will reach the articles being dried, and is directed to the inlet of air supply tube 21A by bathe plate 4S and opening 46 therein. After heating by heater 30A if desired, the air travels downwardly and outwardly from outlet 25A as already described, and air in the space around heat lamps 31, which is out of the main air current, is drawn upwardly through openings 51 to the main air stream as already described.

While a different arrangement of the air supply tube, a different air feedback system, a dierent type of fan and an added top casing and lter have been shown in combination in Figs. 6 and 7, it will be evident that each of these features may be incorporated in the embodiment shown in Figs. l to 4 with or without any of the other features; and all of these features are shown together in Figs. 6 and 7 to avoid a needless multiplicity of drawings and correspondingly lengthy description.

Although but one embodiment of the invention and two modications have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the design and arrangement of the parts without departing from the spirit and scope of the invention, as

the same will now be understood by those skilled in the art. In particular, various types of article supports may be substituted in or used with a drier embodying the invention; and while a compact and effective blower and air heating arrangement have been shown, and this arrangement has special advantages in the form illustrated, other types of air supplying and heating apparatus may be substituted therefor.

I claim:

1. Drying apparatus, comprising a housing forming a drying chamber having a drying zone and including a wall, an air supply tube centrally mounted in said wall and extending into the chamber toward said zone, and a plurality of mountings for directional heat lamps on said wall arranged symmetrically around the air tube and directed toward said zone, said housing including an air outlet at the opposite side of the zone extending around said drying chamber.

2. Drying apparatus, comprising a housing forming a drying chamber 'and including a top, a bottom, and

side walls, an air supply tube extending through the center of the top into the chamber, a plurality of directional heat lamp sockets mounted on the inner face of the top in symmetrical relationship to the supply tube, the lower end of said tube extending to the lower ends of said lamps when in said sockets, a narrow horizontal air outlet passage extending through the side Walls around substantially the entire circumference of the chamber, said chamber being substantially closed during operation except for said air inlet tube and outlet passage, and means for supporting articles to be dried in the chamber in a direct line between said tube and passage.

3. Drying apparatus, comprising a housing forming a drying chamber having a drying zone and having a wall opposite said zone, an air supply tube centrally mounted in said wall and extending into the chamber and directed toward said zone, the inner face of said tube having a zone of reduced cross section forming a venturi throat, an air passage extending from said throat laterally through the tube to the chamber, arranged to draw air from the space surrounding said tube and adjacent said wall into an air stream in the tube and a discharge passage for the air stream opposite said tube on the other side of said zone.

4. Drying apparatus, comprising a housing forming a drying chamber having a drying zone and an upper wall, a heater in the chamber adjacent said wall, an air supply tube centrally mounted in said wall and extending downwardly therefrom with its discharge end directed toward said zone, the inner face of said tube having a zone of reduced cross section forming a venturi throat, and an air passage extending from said throat laterally through the tube into the upper part of the chamber, arranged to draw a heated air from the latter part of the chamber around said tube into an air stream in the tube and a discharge .passage for the air stream opposite said tube on the other side of said zone.

5. Drying apparatus comprising a housing including a top and substantially continuous side walls forming a laterally closed drying chamber, a tubular inlet for drying air under pressure extending downwardly from the top into the chamber and spaced throughout from the side walls, means for maintaining a current of drying air at substantial velocity diverging outwardly and downwardly from said opening for drying articles 1ocated in a drying station in said current, comprising vertically narrow circumferentially extending air outlet means laterally offset from said inlet at opposite sides thereof and located below said station, and radiant heating elements located symmetrically between said tubular inlet and the side Walls and directed downward toward said air current and station.

References Cited in the le of this patent UNITED STATES PATENTS 525,921 Proctor Sept. 1l, 1894 1,589,642 Harris lune 22, 1926 1,717,115 McCann June 11, 1929 1,924,255 Prat Aug. 29, 1933 2,113,770 Richardson Apr. 12, 1938 2,281,184 Dykstra et al. Apr. 28, 1942 2,358,397 Howle Sept. 19, 1944 2,360,257 Muller et al. Oct. l0, 1944 2,376,174 Munning May 15, 1945 2,389,586 Andrews Nov. 27, 1945 2,594,743 Dietert et al. Apr. 29, 1952 FOREIGN PATENTS 161,619 Switzerland May 15, 1933 631,790 Great Britain Nov. 9, 1949

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