US3504444A - Air circulation arrangement for dryers - Google Patents

Description

April 7, 1970 NELSON ETAL 3,504,444

AIR CIRCULATION ARRANGEMENT FOR DRYERS Filed March 25, 1968 4 Sheets-Sheet 1 15 fl/efiz 'ord James 72. )Velaozz Terr] J Zaae April 7, 1970 J. K. NELSON ET AL 3,504,444

AIR CIRCULATION ARRANGEMENT FOR DRYERS 4 Sheets-Sheet 2 Filed March 25, 1968 A ril 7, 1970 J, K. NELSON ET I ,4

AIR CIRCULATION ARRANGEMENT FOR DRYERS Filed March 25, 1968 4 Sheets-Sheet 5 April 7, 1970 J. K. NELSON ET AL 3,504,444

AIR CIRCULATION ARRANGEMENT FOR DRYERS 4 Sheets-Sheet 4 Filed March 25, 1968 United States Patent 3,504,444 AIR CIRCULATION ARRANGEMENT FOR DRYERS James K. Nelson and Terry J. Lane, Eflingham, 111., as-

signors, by mesne assignments, to F edders Corporation,

a corporation of New York Filed Mar. 25, 1968, Ser. No. 715,822 Int. Cl. F261) 21/02 U.S. Cl. 34-131 12 Claims ABSTRACT OF THE DISCLOSURE A clothes dryer having a cabinet receiving a clothescontaining cylinder and a propeller-type fan which are rotatable about a horizontal axis, the fan being located between adjacent rear cabinet and cylinder walls with the cabinet wall having a circular axial orifice affording an air inlet radially inwardly of the fan blades, and the cylinder wall having air discharge openings circumferentially spaced about the axis and located radially outward of, but adjacent to, the outer tips of the fan blades.

This invention relates to an improved air circulation arrangement for a clothes dryer.

There are two basic ways in which a fan of any kind may be applied to a clothes dryer system. These may be called a blow-through configuration and a drawthrough configuration. In a blow-through configuration, the air is drawn from the atmosphere through the fan and through a heater, either upstream or downstream of the fan, and then passes from the fan into the clothes dryer cylinder, through the clothes, and is exhausted. In a draw-through configuration, the air is drawn through a heater, through the clothes dryer cylinder containing the clothes, and then passes through the fan and is exhausted to the atmosphere. From several considerations, it is believed the blowthrough configuration is more advantageous and, accordingly, the invention is directed toward that configuration and does not apply to draw-through type air systems.

In a blow-through fan configuration in a clothes dryer, such as disclosed in U.S. Patent 2,798,307 issued July 5, 1957, and manufactured and sold for many years by Borg-Warner Corporation, it is advantageous to locate the fan on the rear face of the clothes dryer cylinder. This minimizes the amount of duct work required, the fan action itself can be used to achieve an even distribution of the air flowing through passages in the back of the clothes dryer cylinder, and the fan can be readily belted so that it is driven by the motor that also rotates the cylinder. The air flow requirements are relatively high pressure and relatively low flow. For example, in such clothes dryers with a typical clothes load, the fan is required to generate about 1.50 inches of water pressure, and the flow is about 160 cu. ft. per min. Usual considerations of fan application would dictate a forward curve centrifugal impeller be used for such an application. However, the disadvantage of such an impeller is that it works effectively only when provided with a scroll-like housing that effectively converts its velocity energy into pressure energy before discharge from the assembly. Thus, the air is discharged in a single direction, whereas, in the dryer, it is desirable to discharge the air equally in all directions.

Therefore, the only advantageous type of centrifugal fan for this application would be a radial-bladed or backward-curved fan that is capable of converting its velocity energy into pressure within the blading itself. For example, a bladed fan is used in the clothes dryer shown in the above U.S. Patent 2,798,307.

3,504,444 Patented Apr. 7, 1970 SUMMARY OF THE INVENTION A general object of the invention is to provide a new and improved air circulation system for a clothes dryer.

A more particular object of the invention is to provide a novel air circulation system for a clothes dryer and featuring an improved blow-through fan configuration.

Another object of the invention is to provide a unique air circulation arrangement for a clothes dryer and providing optimum performance by insuring maximum air flow and distribution while having an acceptable noise level.

Another object of the invention is to improve clothes dryers by the provision of an air circulation arrangement in which the dryer clothes-containing cylinder and a propeller-type fan are housed in a cabinet and rotatable about a common horizontal axis, with the cabinet and cylinder having adjacent walls providing a chamber for the fan, the cabinet wall having a circular air inlet orifice radially inwardly of the fan blades and the cylinder wall having circumferentially spaced air exit openings located radially outwardly of the fan blades.

Another object of the invention is to provide an air circulation arrangement for a clothes dryer having a rotating clothes-containing cylinder with a fan being located adjacent the rear wall of the cylinder and operable to blow warm air into the cylinder through openings in the wall, the fan being characterized by a multiplicity of blades similar to a propeller fan by being formed with at least the outer blade portions being pitched at an angle to the radial direction thereof in a manner to impart an axial component toward the cylinder wall openings back to the air leaving the blades, the cylinder wall openings being arranged in a pattern having its inner boundary approximately at and outwardly of the radially outer ends of the air-moving portions of the fan blades, with the air inlet to the fan being provided by a circular opening radially inward of the air-moving portions of the fan blades.

The novel features which are characteristic of the invention are set forth with particularity in the appended claims. The invention both as to its organization and operation, together with further objects and advantages thereof, will best be understood by reference to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a vertical sectional view of a clothes dryer embodying the air circulation arrangement of the invention, and taken along the plane of the line 11 of FIGURE 2;

FIGURE 2 is a front elevational view of the dryer shown in FIGURE 1, the front panel being removed and certain parts broken away and partly sectionalized to illustrate details of the dryer;

FIGURE 3 is a perspective view of the dryer, with the basket removed to more clearly illustrate details of the air circulation arrangement including the fan drive;

FIGURE 4 is an enlarged vertical sectional view of the basket rear support and fan mounting assemblies;

FIGURE 5 is a perspective view of the cabinet;

FIGURE 6 is a front elevational view of the fan; and

FIGURE 7 is an edge view of one of the fan blades, taken along the plane of the line 77 of FIGURE 6.

Referring now to the drawings, the domestic clothes dryer is provided with a cabinet generally indicated at 10 having spaced side walls 11 and 12; a rear wall 13; top and bottom walls 14 and 15; and a front wall 16. The front wall 16 has a door 17 hinged thereto and closing an opening, defined by a cylindrical flange 1 8, of the front wall 16, providing access to the front opening 19 of a rotatable clothes container or basket 20, in the form of a cylinder, for loading and unloading clothes in the basket.

The basket is mounted for rotation about a substantially non-vertical axis which, in the present case, is preferably horizontal. More particularly, the basket is substantially cylindrical in shape, having a cylindrical wall 21; a front wall 22 having the opening 19 receiving the flange 18 of the cabinet front wall 16; and a rear wall 23 having a shaft and bearing assembly 24 for the basket and a fan or blower 25. The basket is supported at its front end by spaced supports or skids 26, 26 mounted on the cabinet bottom Wall 15 and having arcuate upper surfaces conforming to the curvature of the cylindrical Wall 21 and provided with shoes 27, 27 of suitable bearing material engaging the basket. The rear end of the basket is supported by the shaft and bearing assembly 24 and, as seen in FIGURES 1 and 5, the basket rear wall 23 has comically-shaped depressed portion 29 providing a mounting means in the form of a sheet-metal hub 30 secured thereto, as by welding, and which hub receives a ball-like bearing 31 secured to a shaft 32 extending rearwardly through a hollow cylindrical portion 33 of a pulley 34 and into a supporting bracket 35 fixed to the rear wall of the cabinet by bolt and nut assemblies 36 as shown in FIGURE 5. The shaft 32 is fixed by pins 28 to the radially-inwardly extending cylindrical portion 37 of bracket 35.

The blower or fan assembly 25 comprises a circular sheet-metal plate having a frusto-conical center portion 38a and radially outer cut-out portions to define a plurality of radially-extending blades 39 each twisted from the plane of the plate and having their radially outer ends connected to and circumscribed by a circular rim 38b. It will be observed the plate is formed as a stamping and in a manner that 6 0% of the projected face area of the plate is devoted to the fan blades, as shown in FIGURES 2, 3 and 6. Referring to FIGURE 5, the center portion 38a of the plate is secured to the pulley 34 rotatably mounted on spaced bearings 40, 40 on shaft 32. The fan is confined between and enclosed by the basket rear wall 23, particularly the conical portion 29 thereof, and the front plate 41 of a duct assembly 42 (FIGURE 1), the rear plate 43 of the duct assembly being spaced from the front plate 41 to provide a passage A therewith. The plate 43 is connected to bosses 44 (FIGURES 1 and 4) formed in and projecting from the cabinet rear wall to provide passages B for the inflow of ambient air by the fan from vents 45 in the cabinet rear Wall and through a plurality of circumferentially and radially spaced openings 46 in the basket rear wall and into the basket interior. As seen in FIGURES 1 and 3, the outer edge of the duct plate 41 is inwardly bent to provide a cylindrical portion 41a having a radially outer annular flange 47 for mounting an annular felt seal 48 fixed thereto by a band 49, the seal engaging the basket rear wall to confine the air between the basket rear wall and the plate 41 for flow into and through the openings 46 in the basket rear wall. It will be noted that the circular rim 38b lies closely adjacent to the cylindrical portion 41a of the duct plate 41 to prevent recirculation of air. The air flows through the basket, and also the openings 50 in an upper collector duct assembly 51 secured to the front wall of the cabinet and providing a passage for flow of air from the basket through a removable lint screen or trap 52 supported in the duct. As seen in FIGURES l and 2, the duct assembly 51 is a rectangular shaped box-like structure having front and rear walls 53, 54; side walls 55; and top and bottom walls 56 and 57, the front wall 53 being secured to the cabinet front wall, the rear wall 54 having the openings 50 defined by an arcuate flange 58 and engaging an annular seal 59 mounted on the cylindrical portion 19 of basket 20 defining the c othes-receiving opening of the 4 basket. The rear wall 54 has its lower portion provided with a flange 61 forming a ledge for supporting the lint screen 52 which is disposed with respect to the duct walls so as to filter lint in the air flowing from the basket through the duct assembly 51.

The air-circulation system further includes a second duct assembly 62 including a cylindrical conduit 63 connected to a funnel-shaped member 64 having a rectangular end receiving a complementary-shaped portion 65, defining the bottom opening of the duct assembly 51. The conduit 63 extends through the rear wall 13 of the cabinet and is connected, in conventional manner, to a standard vent or flue pipe for conducting the moistureladen exhaust to the outside of the house.

While ambient air is drawn into the dryer by the fan through the cabinet rear wall, an air heating assembly 66 comprising, in general, a cylindrical housing 67, which may contain either a conventional electrically-energized heater 68, as shown, or gas-fired heating means, is effective to heat air drawn into and circulated through the housing 67 by the operation of the fan.

The heating assembly 66 is supported on a pedestal P mounted on the bottom wall 15 of the cabinet. The housing 67 extends rearwardiy and is connected to a triangular-shaped housing 70 (FIGURE 3) forming portions of, and connected to, the front and rear plates 41 and 43 of the duct assembly 42, so that the fan is effective to draw heated air in housing 67, through housing 70, into the passage A for mixture of the heated air with the exterior ambient air drawn through passage B, the air mixture being forced into the basket through the openings 47 in the basket rear wall 29.

A belt drive system for the basket and fan is shown in FIGURES l, 2 and 3, the belt drive system being generally indicated at 71 and comprises a bracket 72 having a bottom wall 73 secured to the cabinet bottom wall 15; spaced side walls 74 and 75; and a wall 76 extending between and connecting the side walls and merging with the bottom wall. The bracket 72 has aligned openings in the upper oflset ends of the side walls 74 and 75 receiving pivot members 77 fixed to and projecting outwardly of an inverted U-shaped motor support 78.

The side walls 79 and 80 of the support 78 have their lower ends formed to provide downwardly facing arcuate recesses receiving rubber bushings 81 mounting hubs projecting laterally from the casing of motor M. The bottom ends of each arcuate recess is defined by oppositely extending lugs 83, 83 projecting into slots at each end of an arcuately curved spring retainer of clip 84, the retainers 84 extending under and engaging the motor hub bushings 81 and holding the motor on the support 78. The motor drive shaft 85 extends outwardly of the hub bushings 81 on opposite sides of the motor and have connected thereto drive pulleys 86, 87.

As shown in FIGURES 1 and 2, a V-belt 88 passes around and engages the cylindrical outer surface of the basket. A V-belt 89 is mounted on the drive pulleys 34 and 87 and is operative to rotate the fan or blower 25. An idler pulley 90 engages belt 88 and is rotatably mounted on a bifurcated portion 91 of an arm 92 of a lever 93, the lever being pivotally supported, intermediate its ends, on the motor support side wall 79 by a shoulder bolt and nut assembly 94. The lever has the end of its other arm 95 provided with a slot receiving one end of a tension spring 96, the opposite end of the spring engaging a hook member 97 fixed to the side wall 74 of the bracket 72.

In the operation of the basket and fan drive assembly, rotation of the motor drive shaft in a direction to rotate the pulleys 86 and 87 causes the pulley 86 to activate the belt 88 to drive the basket to tumble the clothes in the basket, while the pulley 87 activates belt 89 to drive the fan to circulate air through the basket and dryer as indicated by the arrows in FIGURE 1.

The improved air circulation arrangement of the present invention is characterized by the novel fan and housing configuration employed in the dryer and providing an increase in air flow by a fan occupying the same or less space than previously-known centrifugal or axial flow propeller fans, and at an equal or lower noise level.

Referring to the drawings, the propeller type fan 25 is steeply pitched and is designed to function partially as a centrifugal fan and partially as an axial-flow fan. The use of a steeply pitched propeller fan in both its centrifugal and its axial-flow aspects is known in other fields and is sometimes called a mixed-flow fan. However, in all cases of which we are aware, the axial-flow aspect occurs at the entrance where the angle to the blading assists the entrance of air. The air is then discharged from the fan radially in a centrifugal manner.

While the dryer fan 25 has both centrifugal and axialfiow aspects, this action is completely different than that in a conventional mixed-flow fan. In fan 25, the centrifugal etfects occur in the inlet condition, and no benefit is derived from the pitch of the blading insofar as the inlet air is concerned. The axial-flow aspects impart a forward angle to what would otherwise be the entirely radial exit of the air from the fan. This is advantageous in directing the air toward the entrance holes 46 in the dryer drum. Thus, while a conventional mixed flow fan has a propeller action that assists the air entering axially and has a centrifugal action that imparts energy to the air discharge radially, fan 25 uses the centrifugal action entirely in the entrance condition, and the combination of the centrifugal and propeller action is used to give a combination of a radial and axial direction to the discharge air. No knowledge is had of a fan with such an action being used in any applicationin fact, in most applications, this action would not be advantageous. However, in the case of clothes dryers, there are advantages to this arrangement over and above those provided by configurations that have heretofore been used.

As previously pointed out, the air circulation arrangement contemplates a blow-through fan configuration in a clothes dryer, having an increase in air flow in a fan occupying minimum space in the dryer and having a low acceptable noise level. Since the air, after leaving the fan blades, has to turn toward and fiow outwardly along the cylinder back wall 29 in order to enter through the openings 46, it can be seen that a fan with angled bladings will contribute to this end. The fan 25, evolved experimentally, was found to have an optimum blade angle of 50. In order to generate the required pressure, a large number of blades was used and a high degree of blade solidarity. That is, it was found desirable to leave as little space as possible between the blades that could not contribute to imparting energy to the air. In order to achieve the desired pressure, it was also found most advantageous to use a very small inlet C so that the inlet of the fan is actually entirely inside the inner radial extent of the blading. The consequent long radial passage makes maximum use of the effect of conversion of velocity energy to pressure energy during the centrifugal action. The use of a large number of relatively narrow blades permits the fan to be fitted in a small axial depth, which is advantageous from the standpoint of allowing the largest possible size of container cylinder for the clothes in a given housing dimension. The fan 25 is also designed so that its multi-bladed arrangement is similar to a propeller-type fan in that at least the outer portion of each blade is pitched at an angle to the radial direction in such a way as to impart an axial component toward the air exit passages or openings 46 in the rear cylinder wall to the air leaving the blades, the openings 46 being arranged in a pattern having its inner boundary approximately at the radial extent of the fan and extending outwardly therefrom, and the inlet C to the fan comprising a circular orifice having its outward extent within most or all of the radial extent of the fan blades.

One of the important aspects of the fan system described here is the relationship of the over-all noise level generated by the fan system to the performance of the dryer. Within the limits of the mechanical strength of the parts, any desired air flow can be generated from any fan system by merely increasing the speed of the fan to a level at which this air flow is achieved. Thus, the air flow achieved in the disclosed dryer could have been achieved in the dryer design of US. Patent 2,798,307 merely by increasing the speed of the fan. However, in doing so, the noise level would be raised to an objectionable degree. Thus, one of the objects of the present fan design is to achieve a better noise level for the same operating characteristics. It was found that with the clothes dryer fan of US. Patent 2,798,307 operating at a speed that would produce the same air flow as the fan 25, the noise level was 4 decibels higher. This illustrates that this application of propeller-like blading of fan 25, in place of the centrifugal blading disclosed in the identified US. patent, is more efficient with respect to noise.

This combination of a many-bladed propeller type of fan to a clothes dryer in a configuration in which a small inlet orifice C is used in such a way that the majority or all of the radial extent of the fan blades is radially outside the dimensions of the orifice, and in which the discharge openings 46 into the clothes dryer cylinder are in a radial pattern at the vicinity of and extending beyond the blade tips, is believed to be novel and makes possible a dryer that is more compact, has a higher air flow, and has a lower noise level for the same performance than those that have been constructed heretofore.

While in accordance with the patent statutes the improved air circulation system has been described in what at present is considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is therefore aimed in the appended claims to cover all such equivalent variations as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a fabric dryer, a casing; a cylindrical fabric container mounted in said casing for rotation about a generally horizontal axis; means defining a substantially closed chamber and including an end wall of said container and a stationary wall supported in said casing adjacent said end wall, said stationary wall having an axially disposed opening therein defining an air inlet into said chamber, said end wall having a plurality of outlet openings therein spaced radially outwardly from and extending circumferentially of said axis defining an air outlet from said chamber for entrance of air into said container; and, a fan of the propeller type rotatably mounted in said chamber about said axis, said fan comprising a plurality of radially extending blades, each of said blades including an outer portion extending to the blade tip disposed at an angle to the radial direction wherein said air inlet opening is disposed radially inwardly of said blade outer portions and said air outlet openings are spaced radially outwardly of said blade Ups.

2. In a fabric dryer as defined in claim 1 wherein said fan includes a circular rim connected to the blade tips and disposed in close proximity to the stationary wall to prevent recirculation of air in the chamber,

3. In a fabric dryer as defined in claim 2 wherein the fan blades are disposed radially outward of the air inlet, and the air outlet openings are disposed radially outwardly of, but closely adjacent to, the blade tips; and the blades occupy a major portion of the fan area with each fan blade being disposed at an angle between 40 to 60 to a plane normal to said axis.

4. In a fabric dryer as defined in claim 3 wherein the fan blades are disposed radially outward of the air inlet, and the air outlet openings are disposed radially outwardly of, but adjacent to, the blade tips; and the fan includes a circular rim connected to the blade tips and disposed in close proximity to the stationary wall to prevent recirculation of air in the chamber, with the blades occupying about 60% of the fan area and with each fan blade being disposed at an angle of about 50 to a plane normal to said axis.

'5. In a fabric dryer as defined in claim 1 wherein said fan is of the propeller type having its blade disposed at an angle to a plane normal to said axis to provide both centrifugal radial air fiow and propeller axial air flow, with centrifugal air flow occurring in the air inlet, and with both centrifugal air flow and propeller air flow occurring in the air discharged from the fan to provide a combination of radial and axial direction to the discharged air to direct the air toward the air outlet passages in the container end wall.

6. In a fabric dryer as defined in claim 5 wherein the fan blades are disposed radially outward of the air inlet, and the air outlet openings are disposed radially outwardly of, but closely adjacent to, the blade tips.

7. In a fabric dryer as defined in claim 5 wherein said fan includes a circular rim connected to the blade tips and disposed in close proximity to the stationary wall to prevent recirculation of air in the chamber.

8. In a fabric dryer as defined in claim 5 wherein the blades occupy about 60% of the fan area.

9. In a fabric dryer as defined in claim 5 wherein each fan blade is disposed at an angle of about 50 to a plane normal to said axis.

10. In a fabric dryer as defined in claim 5 wherein the blades occupy a major portion of the fan area and each fan blade is disposed at an angle between 40 to 60 to a plane normal to said axis,

11. In a fabric dryer as defined in claim 5 wherein the fan blades are disposed radially outward of the air inlet, and the air outlet openings are disposed radially outwardly of, but closely adjacent to, the blade tips; and the blades occupy a major portion of the fan area and each fan blade is disposed at an angle between to to a plane normal to said axis.

12. In a fabric dryer as defined in claim 5 wherein the fan blades are disposed radially outward of the air inlet, and the air outlet openings are disposed radially outwardly of, but closely adjacent to, the blade tips; the fan includes a circular rim connected to the blade tips and disposed in close proximity to the stationary Wall to prevent recirculation of air in the chamber; and the blades occupy 60% of the fan axis, with each fan blade being disposed at an angle of about 50 to a plane normal to said axis.

References Cited UNITED STATES PATENTS 1,072,189 9/1913 Sparks -168 l,377,3 0O 5/1921 Withington.

2,486,058 10/1949 Patterson 34--133 X 2,503,329 4/1950 Geldhof 34133 2,587,646 3/1952 ONeil 34-133 2,608,769 9/1952 ONeil 34-133 X 2,798,307 7/1957 Reiter 34133 2,818,659 l/l958 Hague 34133 X 3,114,653 12/1963 Kruzan 34133 X EDWARD I MICHAEL, Primary Examiner

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