Dryer For Textiles

Abstract

This disclosure teaches a dryer for textiles, particularly laundry from which a preliminary removal of water has been effected. A conventional perforated drum, through which heated air is passed and which is arranged for rotation about a horizontal axis, is provided with ribs on its inner cylindrical wall for tumbling and conveying axially the textiles being dried. The ribs have leading flanks engaging the textiles with angles .alpha..sub.1 preferably at least 20.degree. formed with radii of the drum going through the apexes of the ribs. The ribs have slide plates on their lagging flanks, which slide plates are inclined by acute angles from the apexes of the ribs, so that they convey the goods axially. Rotation of the drum can be in a single sense or it may be reversible.

Parent Case Text

This is a continuation of application Ser. No. 163,389, filed July 16, 1971 and now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a dryer for textiles, particular predried laundry. The dryer has ribs on the inside wall of a cylindrical drum for tumbling and conveying axially the textiles being dried. Hot air flows through perforations in the drum during the drying and removes water from the textiles being dried.

2. Description of the Prior Art

In known dryers operating in accordance with general principles of the present invention, tumbling of the textiles being dried and an increase in drying surface is obtained by rotating the drum, whereby efficiency of drying and loosening of the textiles being dried are achieved.

One such known drum is shown in FIG. 1, the manner of operation of which will be explained here, so as to assure an understanding of the present invention. Carrying along of the textiles being dried over a part of the periphery of drum 1, particularly in the region in which lifting work must be performed, is effected by a plurality of longitudinal ribs 2 arranged on the inner wall of the cylindrical drum. These ribs, which are slender in known machines, i.e., have a small angle .alpha. towards both sides with a height 3; operate in accordance with a scooping principle. In order for satisfactory scooping to be obtained it is important that ribs 2 are slender.

The drying direction of rotation (arrow 4) of drum 1 is fixed. Speed of rotation of drum 1 is adjusted in such a manner that the textiles being dried are in all cases lifted by drum 1 and are dropped down along a curve 5 shown in FIG. 1. The point of separation of a large part of the textiles to be dried which lie further toward the center of the drum is, however, so early that it drops along curve 6. This condition occurs because the centrifugal component, to which the textiles which lie further inside the drum, are subjected, is too small so that rib 2 cannot exert a pushing action thereon.

The disadvantage of the foregoing is that a portion of the textiles to be dried which drops along curve 6 has a relatively short path of fall and is accessible to drying air in a loosened condition for only a relatively short period of time. The textiles to be dried which lie against the wall of drum 1 have such a compact structure that the drying air practically cannot, and does not, act thereon at all. Furthermore, in the case of the textiles which fall along curve 6, the danger of their being rolled up and compacted is present due to their contacting the drum wall. Larger pieces of the textiles, as soon as they have once been rolled together, generally remain in this compacted condition and cannot be dried to the desired extent.

Furthermore in known machines, the textiles to be dried are advanced axially in the drum by means of inclination of the drum or by a directed stream of air. This takes place either after completion of drying in order to empty the drum or for further conveyance within a long drum during the drying process. Dryers of this type are known under the trademark "ORTEX."

There are also known dryers in which the ribs extend obliquely in the drum and are arranged therein in one or more helical threads. Dryers also have been constructed with the sense of rotation of the drum reversible as an additional aid in providing axial movement. The moved textiles to be dried collapse in this case during the stop on reversal of the direction of rotation and they are again available in this form for axial movement. The obliquely extending ribs conduct the textiles to be dried into the stream of hot air which is blown axially into the drum from the rear. (Dryers of this type are also known under the trademark "ORTEX"). These different solutions of axially moving the textiles being dried in the drum, and of improving their tumbling, differ from each other with respect to design of the ribs only with respect to height of the ribs. For axial conveyance of the goods there is required either considerable expenditure in inclining the drum for unloading or else the sense of rotation is reversed, or else such axial movement is desired for another purpose, i.e., to bring the goods back into the stream of hot air.

SUMMARY OF THE INVENTION

The present invention copes with the foregoing problem in a particularly novel, inventive, useful, and facile manner.

It is one object of the present invention to provide a novel and advantageous dryer by which optimum tumbling and rapid axial conveyance of textiles to be dried, particularly for unloading the dried textiles from the dryer is achieved. Attainment of this object is based on a conventional perforated drum of the type described which includes in accordance with this invention ribs with leading flanks (leading relative the sense of rotation of the drum as the ribs engage the textiles) forming an angle .alpha..sub.1 with the radius of the drum going through the apex of the rib which angle is preferably at least 20.degree. and up to about 40.degree. and preferably about 30.degree.. The rib also has a lagging flank forming an acute angle .alpha..sub.2 with the radius of the drum going through the apex of the rib. Said angle .alpha..sub.2 is larger than the angle of friction of the laundry to be dried and exceeds 30.degree.. Preferably it is at least 40.degree. but, of course, less than 90.degree., since at 90.degree. conveying ceases and below 40.degree. friction becomes noticeable and the output decreases considerably. Optimum results are achieved with an angle .alpha..sub.2 equal to 50.degree. to 60.degree.. Said lagging flank is provided with slide plates forming an acute angle .beta. with the radius of the drum going through the apex, for unloading the drum of the goods to be dried, said angle being at least 45.degree.. Preferably said angle is between about 55.degree. and about 70.degree.. Best results are obtained at an angle of about 60.degree.. The upper limit is between about 90.degree. and about 100.degree..

The difference between the angles .alpha..sub.2 and .beta. determines the shape of the slide plates in projection whereby .beta. - .alpha..sub.2 should be greater than 15.degree. so that the slide plate can become effective. With angle .alpha..sub.1 of 20.degree. or greater, the angle of attack of the force acting in the direction of gravity is greater than the angle of repose .delta. in the region of the point of separation of the goods being dried as a result (inter alia) of the interplay between centrifugal force and the weight of the goods.

The conditions for tumbling are changed in advantageous fashion by the development and shape imparted to the ribs in accordance with this invention, because by means thereof an optimum dropping curve (trajectory) is obtained. The particular advantage resides in elimination of a complicated unloading device, due to rapid axial conveyance made possible by virtue of the specially shaped slide plates which form an acute angle with the apex of the rib which apex is parallel to the axis of the drum.

In accordance with one proposed embodiment of the invention, the lagging flanks of the ribs with the slide plates are used for the axial conveyance whereby the textiles to be dried slide down inclined slide plates during the lifting phase.

The ribs themselves can, in special cases, be arranged in a slightly oblique direction with respect to the apex. The height of the ribs is between about 10 percent and about 20 percent and preferably between about 10 percent and about 13 percent.

The angle .gamma. of the slide plates relative the apex can also be more than 30.degree. and is preferably at least 40.degree. in order to obtain rapid axial conveyance. Most preferred is an angle .gamma. equal to 45.degree. to 70.degree.. Best results are achieved with an angle of about 60.degree.. The distance between the slide plates is selected in such a manner, for instance, that a textile piece is conveyed by successive slide plates in turn.

Slide plates can also be movable and insertable in recesses in the ribs whereby an insertion therein is made possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the present invention will be understood more fully from the following detailed description taken with the accompanying drawings in which:

FIG. 1 is an idealized cross-sectional view of a drum according to the prior art.

FIG. 2 is a fragmented perspective front view of a preferred embodiment of a dryer according to the present invention.

FIG. 3 is an idealized cross-sectional view of a drum in accordance with the present invention.

FIG. 4 is a top view of a rib of FIG. 3.

FIG. 5 is an idealized cross-sectional view of a drum with another embodiment of a rib according to the present invention.

FIG. 6 is a perspective view akin to FIG. 4.

FIG. 7 is an idealized cross-sectional view of part of the drum according to this invention with a rib at the position of separation of the textiles to be dried therefrom.

FIGS. 8a and 8b are somewhat idealized cross-sectional views of a drum according to an embodiment of this invention with retractable slide plates.

Like numerals in the Figures indicate like parts.

DESCRIPTION OF PREFERRED EMBODIMENTS

As stated hereinabove, FIG. 1 shows a conventional drum 1 to describe the drop curves (trajectories of the textiles being dried). Triangular-sectional longitudinal rib 2 has height 3 and flank angles .alpha. with respect to a radius of the drum passing through the apex of the rib. The apex of the rib is parallel to the axis of the drum. In addition to drop curves 5 and 6 which have already been described, there is also shown a drop curve 7. Arrow 4 indicates the sense of rotation.

In FIG. 2 perforated drum 1 is arranged in stationary box-like housing 100 of the dryer. Drum 7 is mounted on rollers 9 and rotates thereon driven by reversible drive 10 (coupled to roller 9) which regulates speed and sense of rotation drum 1. Radiator 11 supplies housing 100 with hot air which is conducted through drum 1 due to suction induced by fan 12 which draws air through and discharges it from housing 100. Ribs 102 are provided in the drum to produce tumbling of the goods, introduced into drum through charging door 13. Flap valves 14 are provided in the air intake for regulating hot air flow and for blending fresh air therewith. Brushes 15 are arranged between the inner wall of housing 100 and the outer wall of drum 1 to prevent hot air from flowing around the drum rather than through it and consequently through the goods. Furthermore, the dryer is equipped with air outlet 16, a timer and a thermostat (not shown).

Radiator 11 can be heated, for instance, by steam or electricity. The goods to be dried are introduced into drum 1 through charging door 13. Radiator 11 is then heated. Flap valves 14 are swung toward the side walls of housing 100. Blower 12 draws hot air into drum 1. Fresh air enters the housing 100 through openings 17 provided in its top and thence into and through radiator 11 where it is heated to a desired temperature.

FIG. 3 shows longitudinal rib 102 in accordance with the present invention with a steep leading flank 18 having angle .alpha..sub.1 for tumbling and a flat flank 19 with angle .alpha..sub.2 on which slide plates 20 are mounted for axial conveyance and arranged with angle .beta.. These angles are measured from a radius of the drum which passes through the apex of rib 102. The textiles 21 to be dried form a crescent-shaped pile and are divided by dotted line 22 into two masses, the centers of gravity of which lie on radii 23 and 24 respectively. Arrow 25 in FIG. 3 shows the direction of the view of FIG. 4 and dotted line 26 indicates a "fall shadow" 26 as used herein.

FIG. 4 is a top view of longitudinal rib 102 which has its apex 28 parallel to the axis of the drum and has slide plates 20 in the direction of rotation, indicated by arrow 3 during tumbling and drying and by arrow 27 for axial conveyance or discharge of the dried textiles. Slide plates 20 form an angle .gamma. with apex 28. The direction of sliding of the textiles 21 to be dried is indicated by arrow 29. In the projection of slide plates 20 onto apex 28, path 30 and spacing 31 are defined.

In FIG. 5 there is shown longitudinal rib 103 which rib, with constant direction of rotation indicated by arrows 4 or 27 for drying and axial conveyance, has on its leading flank 108 retractable slideplates 20 which can be adjusted in indicated directions 32 between angles .beta. and .alpha..sub.1, i.e., angle .alpha..sub.2 is variable.

In FIG. 6 there is shown a perspective view of drum 1 with longitudinal ribs 102 and slide plates 20. The various angles .alpha..sub.1, .alpha..sub.2, .beta., and .gamma. are indicated in FIG. 6.

FIG. 7 shows rib 102, depicting resolution of forces between resultant 33 of weight of the textiles being dried and a frictional force or angle of repose .delta. with an angle of rotation of the drum in which the textiles being dried would lift off from the drum if a rib were not present. Resultant 33 acts at an angle .epsilon. which is greater in the region of the point of separation than angle of repose .delta..

If one considers the shape of the pile of textiles 21 to be dried, for instance, the pile of laundry after falling and while it is being accelerated by drum 1 and ribs 102 moving upward, there results in accordance with FIG. 3 the following action. Directly behind a preceding rib there is formed a calm space, in the nature of a leeside-like region (sheltered), which calm space has been referred to herein as the "fall shadow." This "fall shadow" will be limited, in accordance with FIG. 3, by edge 26 herein referred to as the "fall shadow edge." The fall shadow is produced by the time difference upon falling of the textiles being dried between the tip of rib 102 and the inner wall of drum 1, and also, to a similar extent, by the friction by the textiles 21 as a result of a difference in speed between textiles 21 and drum 1. Textiles 21 form a crescent shape, as shown in FIG. 3 which thickens towards the next following rib. This crescent shape is established immediately after the textiles have dropped but it becomes more pronounced as the textiles adjust themselves to the rotation of drum 1 due to friction.

This accumulation of the textiles to be dried, with normal filling of drum 1, reaches a thickness of about 10 to 20 percent of the diameter of drum 1 on rib 102 supporting the textiles, so that when viewing the centrifugal component, one must proceed from individual annular sections, dotted line 22, having different radii 23 and 24 in accordance with FIG. 3. The annular sections are closely interwoven so that textiles with slower speeds are carried along by faster moving textiles. The inner annular section (radius 24) is, however, affected by the centrifugal force to a greater extent than the outer annular section because in the case of the outer section the effect of drum friction and of push by the ribs is felt more strongly.

If the speed of rotation of the drum is so selected that the outer annular section describes the drop curve 5 (FIG. 1), assuming that no rib 2 is present, then in accordance with what has been known up to now, in case of the presence of rib 2 with angle .alpha., the point of separation is pushed out so far that no drop curve occurs any longer. As soon now as the rib is inclined at an angle .alpha..sub.1, as shown in FIG. 3, which is sufficiently large for the angle of engagement of the textiles to be dried on the rib to be greater than the corresponding angle of rest or friction, the textiles can slide along the rib and accordingly separate from the drum at the natural point of separation. The inner annular section, due to its smaller centrifugal component, separates at a somewhat earlier time and it describes drop curve 7 shown in FIG. 1. In this way a narrower region of drop between the drop curves 5 and 7 is obtained which for a given diameter of the drum, affords the greatest possible drying surface.

Furthermore, when considering an individual rib 102 in accordance with FIG. 4, seen in the front view 25 in FIG. 3, let us assume that the drum is rotating in the opposite direction 27. This is the case when the textiles 21 being dried are to be transported further axially in the direction of the drum. Here it is desirable for the textiles 21 to have separated already from the wall of the drum before the natural point of separation. Angle .alpha..sub.2 corresponding to the rear of the rib must therefore be made greater than angle .alpha..sub.1 in order for the textiles to slide down on the rib during the lifting phase, during which the textiles, in any event, are still sliding along the wall of the drum towards the rib.

Slide plates 20 lying within fall shadow 26 of the lagging flank of the rib form and angle .beta. with a plane passing through the drum axis and the apex of the rib, as shown in FIG. 3. Such angle .beta. is always greater than angle .alpha..sub.2, and lies within the angle formed by the fall shadow edge 26 and the noted plane through the apex of the rib. The slide plates 20 perform the following functions. As a result of the sliding movement of the textiles on the rib, the textiles, during one revolution of the drum, move in axial direction over path 30 shown in FIG. 4, provided that the angle of the slide plates is selected sufficiently large that the goods can be advanced thereby. The distance 31 in FIG. 4 is preferably sufficiently small so that a smaller piece of the textiles which is not taken up by one of the slide plates 20, for instance, a handkerchief, can still come into contact with the next following slide plate 20 and slide down the same at least a short distance. In the case of the slide plates, there is primarily of importance the outer edge which faces the fall shadow edge 26 so that individual plates of different length can also be used. In this way, upon change in direction of rotation, a rapid axial conveyance of the goods being dried is possible; which conveyance, after a few revolutions of the drum, completely empties a drum or conveys the textiles further in the case of a longer drum than in a continuously operating dryer.

By an alternate construction, shown generally in FIG. 5 and in detail in FIGS. 8a and 8b, while slide plates 20 are used for axial conveyance of the textiles being dried, there is no reversal of direction of rotation of the drum. In this alternate construction, movable slide plates are arranged on the leading flank 108 of rib 103. As seen in FIG. 5 during the drying process, they do not extend out beyond the rib or angle .alpha.. By control from the outside they are, however, pushed in the inside of the drum during the conveying phase and perform the axial pushing function in the prescribed manner.

FIGS. 8a and 8b illustrate in detail a rib 103 with extendable and retractable slide plates according to the alternate construction. This alternate construction allows use of drum 1 for drying as well as for conveying the goods to be dried, while operating in a single sense (direction) of rotation. The guide plate 20 illustrated in FIGS. 8a and 8b is pivoted around axis 34 and it carries at its outer point roller 35 which runs on movable guiding member 36. Guiding members 36 are arranged around drum 1 in accordance with the pinciple of an iris diaphragm so that they can be brought nearer to the drum or they can be removed farther away therefrom; in the first instance they may form a closed ring. Guide plates 20 are connected each to the other by means of pins 37. Rib 103 is connected pivotally with the drum about apex edge 8. Rib 103 is retained while in the drying position by spring 38 and stop 39. It is evident from FIG. 8a that when drum 1 moves in the direction of the arrow, slide plate 20 is outside of drum 1 and thus slide plate 20 does not interfere with the action of leading flank 108 of rib 103. However, when changing the function of rib 103 whereby it coacts with plate 20 for conveying dried textiles and/or discharging them from the drum as shown in FIG. 8b, movable guiding members 36 are caused to approach drum 1 as is evident from the change of distance between drum 1 and guiding members 36 in FIGS. 8a and 8b respectively. Due to this reduction in distance between drum 1 and guiding members 36, slide plates 20 are moved through suitable slots provided in drum 1 and in rib 103 and are pivoted around fulcrum 34 whereby they penetrate into drum 1. Flanges 40 on slide plates 20 serve as stops on rib 103. Rib 103 is pivoted at the same time around its upper edge 8 in counteraction to spring 38. Accordingly a single sense of rotation accommodates both drying and discharging of the textiles.

It should be understood that angles given in this specification of preferred embodiments are in large measure for the sake of illustration. It is possible to describe the apparatus according to this invention without limiting it to such angles. In this connection the force which results from movement of drum 1 and the weight of textiles 21 as it is exerted at the point of liftoff upon leading flank 108 of rib 103 must be large enough and must be oriented so that the component along said leading flank 108 is greater than the frictional resistance exerted by leading flank 108. Coaction of a number of parameters takes place, more particularly weight of the textiles (which is dependent upon degree of moisture therein), linear speed of rib 103 (which is dependent upon the diameter of drum 1 and upon its speed of rotation), coefficient of friction (which depends upon the material and manner in which leading flank 108 of rib 103 has been finished) and angle of inclination of leading flank 108. Except as specified in the claims, statements regarding the values of the angles disclosed in this specification are not intended to be limiting.

By means of the drum in accordance with the present invention, it is possible to obtain both an excellent fall curve or trajectory (tumbling) as well as a rapid axial conveying of the textiles being dried. By the development of the ribs for the axial conveyance, each drum dryer has, at only slight expense, a dependable automatic emptying device so that the drum of the invention can be used advantageously also in continuous drying machines.

It will be apparent to those skilled in manufacture and/or operation of dryers that wide deviations may be made from the embodiments set forth herein, without departing from the main theme of invention set forth in the claims which follow.

Claims

I claim:

1. A dryer for textiles, particularly laundry, from which a preliminary removal of water has been effected, and comprising in combination:

a. a housing which encloses a chamber, said housing being provided with an air inlet and an air outlet each in flow communication with said chamber;

b. a cylindrical drum mounted in said chamber between said air inlet and said outlet, and means for rotating said drum about a substantially horizontal axis, said drum having an inner wall and being formed with a plurality of perforations;

c. a fan connected operatively to the housing and arranged for moving air from said air inlet through said drum to said air outlet;

d. at least one rib substantially triangular in cross section mounted adjacent said inner wall of said drum for tumbling the goods being dried, the apex of said rib extending radially into said drum and being in a plane parallel to the axis of said drum; and

e. a plurality of slide plates mounted adjacent to said rib and normal to said drum, said plates being inclined relative to a plane defined by and including said drum axis and said apex so as to form an acute angle with said apex, said plates being out of contact with the goods when the latter are dried during tumbling and serving to convey said goods axially of the drum during unloading of the goods from the drum following drying thereof.

2. The dryer of claim 1 wherein said slide plates are stationary and further including means for rotating said drum in one direction during the tumbling cycle and in an opposite direction during the unloading cycle.

3. The dryer of claim 1 further including means for pivotally mounting said slide plates on said inner wall of said drum for movement between a first position substantially withdrawn from the inner wall of said drum during the tumbling cycle, and a second position extending radially inwardly from said inner wall during the unloading cycle, and means for moving said slide plates between said first and second positions.

4. The dryer of claim 3 wherein said drum and rib are provided with a plurality of aligned recesses, each of said slide plates extending through said recesses when said slide plates are moved into said second position.

5. The dryer of claim 3 wherein said means for moving said plates comprises a roller carried by each of said plates, and a movable guide member mounted radially outwardly of said drum in contact with said rollers, and means for moving said guide member radially toward or away from said drum thereby to move said slide plates between their first and second positions.

6. The dryer of claim 5 wherein said rib is pivoted at the apex thereof relative to said inner wall of said drum, and resilient biasing means operatively connected to said rib for biasing the leading flank of said rib toward said inner wall of said drum when said guide member is in its withdrawn position.

7. The dryer of claim 1 wherein said rib includes a leading flank and a lagging flank, with the leading flank forming an angle of at least 20.degree. with the radius of the drum going through said apex of said rib, and the lagging flank forming an angle with the radius through said apex which is greater than the angle of 20.degree..

8. The dryer of claim 7 wherein said angle between said lagging flank and said radius is greater than 45.degree..

9. The dryer of claim 1 wherein the slide plates are substantially triangular in shape and form with said plane an angle greater than 45.degree. thereby to effect axial movement of the goods during the unloading cycle.