US 2718066 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Sept. 20, 1955 J ENGEL 2,718,066
LAUNDRY DRYERS Filed Jan. 2, 1952 J- ANTHDHYENBEI ATTUH NEY United States Patent LAUNDRY DRYERS J Anthony Engel, Syracuse, N. Y., assignor to Easy Washing Machine Corporation, Syracuse, N. Y., a corporation of Delaware Application January 2, 1952, Serial No. 264,527
6 Claims. (Cl. 34-45) This invention relates to laundry dryers, and more particularly to a control system and operating cycle therefor.
In dryers of the type described, there is generally employed a tumbling drum for laundry operating in conjunction with air heating elements, and means for circulating or translating heated air through the drum, together with various independent thermostatic controls. Such an arrangement is disclosed in my application Serial No. 262,066, filed December 17, 1951.
The present invention is directed to a system wherein a single manual control is utilized for commencing a cycle of operations, and in which a single thermostatic control is utilized for effecting over-all subsequent control over the heating element, tumbling drum and air circulation, whereby the various functions are commenced and terminated in an efiicient, shortened cycle dependent on the minimum length of time required to reach various controlling temperatures. Such control includes in the present arrangement a thermo expansion element actuated by differentially operating heat sensitive units suitably located within the dryer cabinet.
The invention is further directed to a dryer control system particularly adapted to effect drying to a large extent by evaporation induced by radiant heat, in which air utilized for carrying off evaporated moisture is exhausted at a temperature not greatly exceeding room temperature, and in which the temperature within the cabinet is allowed to rise prior to circulation of air, so as to minimize wastage of heat in the initial operation and to provide a shortened cycle. In such an arrangement, when circulation commences, there is a temperature drop likely to interfere with the proper operation of the single thermostatic control. Through the use of differential acting heat-sensitive units, an increase in exhaust air temperature is utilized to compensate for such temperature drop, whereby the single thermostatic control is rendered operable.
The above and other novel features of the invention will appear more fully hereinafter from the following detailed description when taken in conjunction with the accompanying drawings. It is expressly understood that the drawings are employed for purposes of illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.
In the drawings, wherein like parts are indicated by.
forate revolving laundry-containing drum 14. The drum 14 may be of the type commonly in use having an access door in the front wall thereof in alignment with a front wall cabinet access door, such parts not being shown since they form no part of the invention.
The drum is adapted to be rotated at a tumbling speed by a motor 16 through a belt drive 18. The casing 12 in an upper portion thereof is provided with an electrical heating element 20 of the infra-red radiant type, and adjacent such element are a number of inlet louvres 22 to permit entrance of air from within the cabinet 10 into the casing 12. Air is withdrawn from the casing 12 through a duct 24 having a centrifugal blower 26, belt driven as at 28 by the motor 16. Air exhausted from the casing 12 is delivered to the surrounding atmosphere through an exhaust port 30.
Control over the operation of the machine is made dependent upon the temperature within the casing 12, through the employment of a thermostatic device of the type, for example, comprising sealed bulbs connected to a switch actuating expansion bellows. For this purpose, the sealed bulbs 32 and 33 are located within the casing 12, such bulbs being connected together by conduits 35 and 37 to a single conduit 34 leading to a thermostatic control switch assembly 36 located conveniently on an inclined rear cabinet panel 38. The control switch (See Figure 2) comprises a casing 39 having a front panel 40 through which projects a push knob control 42, the knob being mounted upon a pin 44 slidable in a boss 46 on the inside surface of the panel 40. Such pin is provided with a flange 48 adapted to engage a spring contact leaf 50, the contact leaf being adapted by movement of the knob 42 inwardly to engage the contact leaf 52 to close an electrical circuit through contacts 51 and 53 for the purpose of energizing the heating unit 20.
A spring-pressed ball detent 54 mounted in the boss 46 is adapted to engage an annular groove 56 in the pin 44, so as to hold the knob 42 in its inward position against the urge of the leaf spring 50. The structure thus described is adapted to close a circuit through a relay coil 58 which in turn closes contacts 60 adapted to energize the heater coil 20 by completing a connection to a standard sourse of supply of 220 v. The thermostatic bulbs 32 and 33 and the conduits 34, 35 and 37 lead to a closed expansion chamber 62 mounted inside the rear Wall 64 of the casing 39, such chamber being of generally hat-shaped section. The rim flange 66 is adapted to bear against a casing partition member 68. Within the chamber 62 is a sealed bellows 76 having an external flange 72 held against a shoulder 73 on the internal wall of the chamber 62, an annular sealing disk 76 acting to rigidly hold the bellows in place with its flange 72 in sealed engagement with the shoulder 74.
Slidably mounted through an aperture 73 in the partition wall 68 is a sleeve member Sit having a rear shoulder 82 adapted to be engaged by the end wall 84 of the bellows 70, such sleeve being adapted to be resiliently held against the bellows by a coil compression spring 86 bearing against the shoulder 82 and the partition 6%. Threaded within the sleeve 8t? for adjustment purposes is a pin 88 having an insulating tip 99 adapted to bear against a resilient contact leaf 92. Such contact leaf carries a contact 93 adapted to engage with a contact 94 mounted upon a contact arm 96. The leaves 54 52 and 92 are mounted upon an insulating multiple bracket member 98, and the contact arm 96 is supported upon an insulating bracket member 100.
The contacts 93 and 94 on the contact leaf 92 and arm 96 are connected to a solenoid 108 which in turn actuates switch contacts 110 in circuit with the motor 16, such motor for convenience being connected between one side of the 220 v. line and the neutral connection.
It will be seen that the thermostatic bulbs 32 and 33 are so arranged within the casing 12 as to be responsive to an increase in temperature within the casing. When the manual button 4-2 is moved inwardly to close the circuit between the contact leaves 50 and 52, the infra-red heater is energized, and upon the temperature within the casing 12 reaching a predetermined temperature such as 170 F., the expansion of the fluid within the bulb 32 is sufiicient to cause the bellows 70 to move the pin 88 enough so as to in turn bend contact leaf 92 to close a circuit between contacts 93 and 94. Thus, the motor 16 is energized, causing rotation of the laundry-containing drum, as well as positive circulation of air through the drum.
As soon as the drum commences to rotate and the blower 26 commences circulation of air through the casing 12 and drum 14, there is a drop in the temperature within the casing in the region of bulb 32 which would tend to cause the motor starting contact 93 to separate from the contact 94, cutting off the motor. In order to prevent such an occurrence, the bulb 33, located in the discharge outlet 24 becomes heated somewhat by the temperature of the air within the casing 12 being discharged therethrough, it being apparent that as soon as the motor 16 is energized, the blower 26 draws the heated air within the casing 12 across the bulb 33. The net differential effect of the slight cooling of bulb 32 is compensated for by the heating of the bulb 33, so that the contacts 93 and 94 remain closed. In practice, a drop in temperature in the region of bulb 32 of 3550 may be expected, and an increase from room temperature of 70 to 105 120 may be expected at the outlet bulb 33, when circulation commences.
The tumbling of the clothes is effected by rotation of the drum 14 which is heated in its passage past the infrared heating coils 20. By such an arrangement, the infra red heating coil 20 effects evaporative drying action of the tumbling laundry by radiation primarily, and by contact of the heated drum with the clothes. The blower 26 circulates or translates air through the drum at a low rate whereby to exhaust air from the drum as it accumulates moisture evaporated from the laundry. The laundry within the drum is preferably retained at a low temperature, for example, in the range of 135, to effect an efficient drying operation, it being appreciated that the higher the temperature of the air exhausted from the blower 26, the lower is the efficiency of the apparatus. It Will be highly desirable to have the air exhausted as little above room temperature as possible, so as to minimize the heat lost merely through excess heating of the air circulated through the dryer. Thus the heat added to air entering through the louvres 22 by the heater 20 is preferably equivalent to that consumed by evaporation within the tumbling drum. By utilizing a low rate of air flow, the entering air may be heated to a higher temperature, more effective for evaporative purposes, and yet discharge at a low temperature.
So long as evaporation of moisture from laundry contained within the drum continues, such evaporation acts to reduce the temperature of the air as it circulates there through. However, as the laundry approaches a dry state, the rate of evaporation reduces, and the cooling effect of such evaporation is substantially reduced, so that the temperature within the casing tends to increase. When the laundry becomes substantially dry, evaporation substantially discontinues, and when this occurs, the temperature within the casing 12 rises at a relatively rapid rate, the rapid rate being in part due to the low rate of air circulation. The temperature in the region of bulbs 32 and 33 increases. This factor is utilized to open the circuit to the heating element 20 to discontinue the drying operation. In order to effect this result, the pin 88 actuated by the thermostatic bellows '70 is adapted to resiliently bow the contact leaf 92 into engagement with the manually operated push pin 44 moving the same sufiiciently outward to release the detent 54 so that the spring contact leaf 50 will return the manual control 42 to the off position as shown.
At this point, the infra-red heating coil 20 is deenergized. The motor 16, however, continues to run, tum bling the laundry within the drum and drawing air through the casing, discharging the same through the outlet 30. The temperature gradually decreases within the casing 12, and when the temperature drops to the bulbs 32 and 33 which actuate the thermostatic bellows have caused such bellows '70 to retract sufficiently to cause the leaf contact 93 and 94 to separate, opening the circuit to the motor 16 and the resistor 108.
In Figure 3, the temperature at the thermostatic bulb 32 is indicated by curves illustrating a typical cycle. At the point 112, the temperature has risen to approximately 170, at which time the motor 16 is energized. After this, there is a drop in temperature for the reasons previously set forth; the motor continuing to run, and the curve continues relatively flat at a temperature of or thereabouts for a period until substantially all the moisture is evaporated from the laundry contained within the drum. Such point is roughly indicated as at 114-. The temperature thereafter rises to the value indicated at 116 when the infra-red heating coil 20 is de-energized, and thereafter, the motor continues to rotate the drum and draw air therethrough until the temperature drops to a value indicated approximately at 118, or 120 B, when the motor circuit is broken.
It Will be appreciated that any particular temperature limits for effecting the operations described may be selected, it being the primary object of the invention to quickly build the infra-red radiation within the drum prior to commencing rotation and ventilation. Since the heating coil 20 is located near the top of the drum, laundry in the bottom. of the drum, when not rotating, is in a safe place, and will be protected from undue heating effect during this period, even though the temperature created within the drum is allowed to build up to a value in excess of the operating temperature during drum rotation. Since it is desirable to dry to a large extent by eflicient radiation and physical contact, rather than by excess heating of large amounts of air, it is desirable to have the radiation effective before any forced circulation of air through the drum takes place. However, thereafter, the circulation of air through the drum is sufficient to assist the evaporation of moisture by radiation by carrying off moisture at approximately the rate of evaporation. It is not, however, desired to heat the air entering the drum to any substantial degree, other than for the purpose of aiding evaporation and compensating for the cooling effect of evaporation within the drum, and it is not desired to flow substantial quantities of air through the drum. Consequently, evaporation is balanced against the quantity of heat imparted to the air entering the drum so as to maintain a relatively low temperature of the air being discharged. The air entering at a low volumetric rate is heated to provide the necessary heat value to be expended in evaporation.
Upon the near completion of the drying of the laundry, the temperature rises substantially above the low temperature value referred to. This temperature rise serves as an indication that the drying operation is completed or susbtantially completed, and is utilized to discontinue the operation of the infra-red heating coil, following which the drum rotation and air circulation is continued until the laundry is reduced to a temperature safe to handle without discomfort. It will be understood that the air flowing through the discharge outlet in the region of bulb 33 will be more near room temperature than the air at the bulb 32, and that the positions of the bulbs may be varied somewhat to provide an optimum control situation dependent upon the differential effect of air temperatures within the drum in the regions of the heater element 20 and the discharge outlet 26.
From the foregoing, it will be seen that provision is made for quickly bringing the apparatus to a temperature for effective drying before air circulation commences, and that the drying time thereafter is automatically controlled by the temperatures existing within the easing, resulting from the balance of evaporation and heat introduced by the moderate flow of air therethrough. With the varying loads, the length of drying time is automatically varied in proportion. Although solenoids 58 and 108 have been shown for closing the various power circuits, it will of course be understood that the contacts 51 and 53 and 93 and 94 may be interposed in place of the solenoid contacts 60 and 110, if it be desired to directly control the power circuits, and thereby eliminate such solenoids. Any safety thermostatic switch such as 120 may be inserted in the heater coil circuit. Such switch would only operate should the temperature within the casing rise to a danger point due to failure of the mechanism to function properly.
Although a single embodiment of the invention has been illustrated and described, it is to be understood that the invention is not limited thereto. As various changes in the construction and arrangement may be made without departing from the spirit of the invention, as will be apparent to those skilled in the art, reference will be had to the appended claims for a definition of the limits of the invention.
What is claimed is:
1. In a laundry dryer, a housing, a rotatable tumbling drum contained therein, means for rotating said drum, means for heating air within said housing, means for translating air heated by said heating means through said drum and exhausing such air outside said housing, means for activating said heating means, a single expansible chamber thermostatic device for activating said translating means upon establishment of a drying temperature in said cabinet, and deactivating said heating means upon establishment of a temperature elevated above said drying temperature, and two heat-sensitive units connected in parallel and to said expansible chamber device for actuating said device, one of said units being exposed to said heating means, and the other being exposed to the temperature of the exhausting air.
2. In a laundry dryer, a housing, a rotatable tumbling drum contained therein, means for rotating said drum, electrical means for heating air within said housing, means for translating air heated by said electrical means through said drum and exhausting such air outside said housing, a switch for closing a circuit to said heating means, a single expansible chamber thermostatic device for activating said translating means upon establishment of a drying temperature in said cabinet, and deactivating said heating means upon establishment of a temperature elevated above said drying temperature, and two heatsensitive units connected in parallel and to said expansible chamber device for actuating said device, one of said units being exposed to said heating means, and the other being exposed to the temperature of the exhausting air.
3. In a laundry dryer, a housing, a rotatable tumbling drum contained therein, motor means for rotating said drum, means for heating air within said housing, means for translating air heated by said heating means through said drum and exhausting such air outside said housing, a switch for closing a circuit to said motor means and said translating means, means for activating said heating means, and a single expansible chamber thermostatic device including two heat-sensitive units connected in parallel and with said device for closing said switch upon establishment of a drying temperature in said cabinet, and for deactivating said heating means upon establishment of a temperature elevated above said drying temperature, one of said units being located near said heating means, and the other being exposed to the temperature of exhausting air.
4. In a laundry dryer, a housing, a rotatable tumbling drum contained therein, motor means for rotating said drum, electrical means for heating air within said housing, means for translating air heated by said electrical means and exhausting such air outside said housing through said drum, a switch for closing a circuit to said motor means and said translating means, a switch for closing a circuit to said heating means, and a single expansible chamber thermostatic device for closing said first-named switch upon establishment of a drying temperature in said cabinet, and for opening said heating means switch upon establishment of a temperature elevated above said drying temperature, said thermostatic device including heatsensitive units connected in parallel and with said device, one located adjacent said heating means, and another located so as to be sensitive to the temperature of air exhausted by said exhausting means.
5. In a laundry dryer, a cabinet, a perforate rotatable drum contained therein, electrical heating means within said cabinet, including motor means for rotating said drum, means for translating air through said heating means drum and in contact with fabrics contained therein, and exhausting said air outside said cabinet, a switch for closing a circuit to said motor means, a switch for closing a circuit to said heating means, said switch being yieldingly held closed upon actuation thereof, an expansible chamber thermostatic device including two units connected in parallel and with said device, and located so as to react to a temperature in said cabinet adjacent said heating means and the temperature of air exhausted by said exhausting means for closing said first-named switch upon establishment of an eiiective drying temperature in said cabinet, and means for opening said heating means switch responsive only to movement of said device through a range of movement beyond said initial range, and in response to temperatures elevated above said drying temperature.
6. In a laundry dryer, a casing, a tumbling drum therein, a motor for driving said drum, an air heater, an air inlet, an air exhaust, and means driven from said motor for translating heated air through said drum and discharging such air into said air exhaust and into the surrounding atmosphere, a switch manually movable for energizing said heater, a switch for energizing said motor, and an expansible chamber thermostatic device having two heat-sensitive units connected in parallel and with the device acting in response to the temperature within said casing at two remote points for closing said motor switch whenever the temperature within the casing reaches a predetermined drying temperature, said lastnamed means acting to actuate said manually movable switch to de-energize said heater upon a predetermined further increase in the temperature within said casing, one of said units being sensitive to air temperature in the region of said heater, and another sensitive to air temperature in said air exhaust.
References Cited in the file of this patent UNITED STATES PATENTS 1,707,547 Adams Apr. 2, 1929 2,398,880 Broglie Apr. 23, 1946 2,524,438 Graves Oct. 3, 1950 2,564,867 Weber et al. Aug. 23, 1951 2,583,850 Kauffman II Jan. 29 1952