US2838845A - Control circuits for clothes drying machines - Google Patents

Description

June 17, 1958 c. E. ERICKSON CONTROL CIRCUITS FOR CLOTHES DRYING MACHINES Filed May 29, 1956 3 Sheets-Sheet 1 FIGS 1 60 INVENTOR. CZzfford E Erickson June 17, 1958 c, ERIQKSQN 2,838,845

CONTROL CIRCUITS FOR CLOTHES DRYING MACHINES Filed May 29, 1956 3 Sheets-Sheet 2 Variable Fixed 40' 3 Wire M6298! Timer Sw. Z

56/77/79 5w Warm 75 Off Gear 7min f/iermcz/ 34b Cufouf g5 Heaf/ 0m 34 INVENTOR.

U/iffard ATE/[M5022 BY dm cw) w 2 m June 17, 1958 c. E. ERICKSON CONTROL CIRCUITS FOR CLOTHES DRYING MACHINES 5 Sheets-Sheet 3 Filed May 29, 1956 INVEN TOR. U/1'ff0/c KEr/cison United States Patent CONTROL CIRCUITS FOR CLOTHES DRYING MACHINES Clifford E. Erickson, Chicago, 111., assignor to General Electric Company, a corporation of New York Application May 29, 1956, Serial No. 588,056

Claims. (Cl. 34- 45) The present invention relates to control circuits for clothes drying machines of the home laundry type, and more particularly to an improved control circuit for a clothes drying machine of the character of that disclosed in U. S. Patent No. 2,686,373, granted on August 17, 1954, to Clifford E. Erickson.

It is a general object of the invention to provide a control circuit for a clothes drying machine that incorporates improved facility for selectively setting the desired heating rate of the electric heating unit thereof that is to be maintained in the clothes drying operation of the machine.

Another object of the invention is to provide a clothes drying machine control circuit that incorporates improved facility for selectively setting different heating connections between the electric power source thereof and the electric heating unit thereof so as to set corresponding different heating rates of the heating unit in the clothes drying operation of the machine.

A further object of the invention is to provide a clothes drying machine control circuit of the character noted, wherein the facility mentioned essentially comprises electric switches that may be selectively set for the heating rate control purpose.

' A still further object of the invention is to provide an electric heating system for a clothes drying machine, or the like, that is of improved and simplified connection and arrangement.

Further features of the invention pertain to the particular arrangement of the elements of the clothes drying machine control circuit, whereby theabove-outlined and additional operating features thereof are attained.

The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic lateral sectional view of a clothes drying machine of the home laundry type that incorporates a control circuit embodying the present invention;

Fig. 2 is a diagrammatic longitudinal sectional view of the clothes drying machine as shown in Fig. 1;

Fig. 3 is a schematic diagram of the electric control circuit incorporated in the clothes drying machine and embodying the present invention;

Figs. 4 to 9, inclusive, are schematic diagrams of the different heating connections that are completed between the electric power source and the electric heating unit in the corresponding different positions of the manually operable pushbutton switch that is incorporated in the control circuit shown in Fig. 3; and

Fig. 10 is a graphical representation of the temperature variations in two identical clothes drying machines respectively incorporating a conventional control circuit and the control circuit embodying the present invention illustrated in Fig. 3.

Referring now to Figs. 1 and 2 of the drawings, the clothes drying machine 20 there illustrated is of the home 2 laundry type and of the general construction and arrangement of that disclosed in detail in the previously mentioned Erickson patent, and comprises a control circuit embodying the features of the present invention. Specifically, the machine 20 comprises an upstanding housing, not shown, that encloses an upstanding casing 21, that, in turn, encloses a substantially cylindrical drum 22 that is mounted for rotation about its longitudinal axis disposed in a substantially horizontal position. The drum 22 includes a substantially cylindrical perforated side wall 23, a substantially circular imperforate rear end wall 24, and a substantially circular front end wall 25 having a substantially centrally disposed front opening, not shown, formed therein and aifording access to the interior of the drum 22. The housing, not shown, that encloses the casing 21 is provided with a front wall having a front opening formed therein and affords access through the drum front opening itno the interior of the drum 22; which housing also carries a front door, not shown, operatively associated with the cabinet front opening. The drum 22 is mounted for rotation upon a stub shaft 26 that is secured to the rear end wall 24 thereof. The casing 21 includes a substantially tubular side wall 27 and rear and front end walls 28 and 29; and a battle 38 is arranged below the bottom of the drum 22 and above a sump 31 formed in the bottom of the tubular side wall 27. The configuration of the tubular side Wall 27 of the casing 21 is generally scroll-shaped, so that it cooperates with the cylindrical side wall 23 of the drum 22 to provide a fan casing so that the mere rotation of the drum 22 in the counterclockwise direction, as viewed in Fig. 1, brings about the circulation of a current of air through the drum 22 and through the casing 21.

More particularly, a bafiie 32 is arranged in the upper right quadrant of the tubular side wall 27, as shown in Fig. l, and cooperates therewith and with the associated cylindrical side wall 23 of the drum 22 to define a heating chamber 33; which heating chamber 33 has a heating unit 34 disposed therein. In the arrangement, the bathe 32 also constitutes a heat reflector for the purpose of reflecting radiant energy from the electric heating unit 34 onto the cylindrical side wall 23 and through the perforations therein onto the clothes contained in the drum 22; and the upper portion of the tubular side wall 27 of the casing 21 carries a layer 35 of thermal insulation. The lower portion of the tubular side wall 27 of the casing 21 cooperates with the bafile 30 to define a condensing chamber 36 therebetween; and the opposite ends of the baffle 30 terminate short of the adjacent portion of the tubular side wall 27 to define two spacedapart and communicating passages therebetween. Further, the cylindrical side wall 23 of the drum 22 comprises a plurality of substantially equally spaced-apart inwardly disposed clothes tumbling vanes 37, three being illustrated, that bring about tumbling of the clothes, indicated at 38, when the drum 22 is rotated into the counterclockwise direction as viewed in Fig. l. The vanes 37 and the clothes 38 tumbling in the drum 22 also assist in the circulation of the current of air through the drum 22 and within the casing 21; whereby a current of air is circulated from the heating chamber 33 through the drum 22 into contact with the contained clothes 38 tumbling therein and thence via one of the passages previously mentioned through the condensing chamber 36 and then via other of the passages previously mentioned and back into the heating chamber 33.

The current of air is heated and dried in the heating chamber 33 by the electric heating unit 34; whereby the clothes 38 tumbling in the drum 22 are heated and dried by the current of air. In the condensing chamber 36, a spray of cool water is provided, as explained more fully hereinafter, whereby moisture contained in the current of, air is, condensed therefrom, and accumulated in the sump 31. Also the spray of cool water in the condensing chamber 36 scrubs the current of air circulated therethmugblemoving linttherefrom; whereby the water, the, condensate; and the; lint accu-mulate'in the sump 31 and; are, removed to the exterior of the machine 2t) via a drainiconduit-39 that is connected to an associatedpump 40; that communicates with drain plumbing, not shown.

As, shown in Fig. 2, the arrangement for rotating the drum: 22. and for operating the pump 40 comprises an electric drive-motor 41 provided with an operating shaft 421carrying two pulleys 43 and 44. The pulley 43 is beltedto a pulley 45 carried by the pump shaft 46; while thepulley 44 is belted to a pulley 47 carried by an idler shaft; 48, that also carries a pulley 49. The pulley 49 isb elted to a pulley 50 carried by the drum shaft 26 that is, secured to the end wall 24- of the drum 22. Accordingly, it will be understood that when the drive motor, 41 is operated, the drum 22 is rotated in the counterclockwise direction, as viewed in Fig. l, and the pump; 40 is operated to discharge the water, the, condensate and the lint from the sump 31 formed in the bottom ofthe-casing 21.

Also the machine 20 comprises a cooling water supply system including an inlet conduit 51 that is adapted to be supplied with cool water under gauge pressure from the city water main, a communicating fixture 52 housing a strainer, not shown, a communicating flow regulator 53, a: communicating control valve 54, a communicating tube 55, and-a-communicating jet nozzle 56. The control valve 54 is of the solenoid-controlled type being provided with an operating solenoid indicated at 54a, the control valve. 54. being biased into its closed position and being operated into its open position when the solenoid 54a is; energized. The jet nozzle 56 is arranged in alignment with a hole 57 formed'in the rear end wall 23 of the casing 21 and below the bafiie 30; and within the condensing chamber 36 there is arranged a target 53 disposedin alignment with the hole 57; whereby the stream of. water projected from the jet nozzle 56 and passing through thehole 57 impinges upon the target 58 breaking-up the same and producing the spray of cool water in the condensing chamber 36, as indicated at 59, and as previously explained.

Also the machine 20 comprises certain auxiliary control equipment, including a high temperature thermal,

cutout switch, indicated-at 66 in Fig. l, and a hydrostatic pressure cutout switch, indicated at 61 in Fig. 1, the switches, 60 and 61 being best shown in Fig. 3. Specifically, the switch 60 is of the thermostatic type including a bimetallic heat-responsive element 62 controlling a pair of movable contacts 63 and 64 that respectively cooperate with a pair of stationary contacts 65 and 66. Thethermal element 62 normally biases the movable contacts 63 and 64 into their closed positions with respect to the contacts 65 and 66, moving the contacts 63 and 64 into open position with respect to the contacts 65 and 66 only in the event of an unusually high temperature of the thermal element 62 in the zone within the casing 21 in which the thermal cutout switch 66 is disposed. Specifically, the switch 61 is of the hydrostatic type including a movable bellows 67 arranged to be responsive to the head of water accumulating in the sump 31, and a contact bridging member 68 selectively controlled thereby, the contact bridging member 68 governing an associated contact pair. In the arrangement, the bellows 67 biases the contact bridging member 68 into its closed position, operating the same into its open position, only in the event of accumulation of an unusual head of water in the sump 31.

As shown in Fig. 3, the drive motor 41 is of the splitphase type including a start winding 69, a run winding 70, and an inductively coupled rotor 71 supporting the operating shaft 42 and carrying a start and run control switch 72 of the speed-responsive typeand including two operable heating rate control switch 77; which elements may be carried by the backsplash of the housing, not shown, in a conventional manner.

Specifically the master timer switch 75 comprises a manually rotatable dial 78 provided with a rotatably mounted operating shaft 79 carrying four insulating control cams C1, C2, C3 and C4, which respectively cooperate with four sets of switch springs S1, S2, S3. and S4. Further, the master timer switch 75 comprises an electric timer motor M1 of the synchronous type and provided with an operating shaft 80 that is connected to a gear train 81 that is provided with an operating shaft 82; the operating shafts 79 and 82 being interconnected by a slipclutch 83. The manual dial 78 has an off position and a variable on position; whereby operation ofthe manual dial 78 out of its off positioneffects rotation of the operating shaft 79 relative to the operating shaft 82 by virtue of the provision. of the slipclutch 83 so that the control cams C1, C2, C3 and C4 selectively govern the sets of switch springs S1, S2, S3

and S4, respectively. Rotation of the manual dial 78'.

out of its oif position effects operation of the timer motor M1; whereby the operating shaft 80 thereof effects rotation of the operating shaft 79 through the gear train.

81, the operating shaft 82 and the friction, clutch 83, so that the operating shaft 79 is further rotated one complete revolution and ultimately back into its off position.

The heat-setting switch 76 is' of the pushbutton type andof the general construction andarrangement oftthat disclosed in U. S. Patent No. 2,431,904, granted on;

December 2, 1947, to John L. Andrews; which switch76 comprises six individual pushbuttonsdesignated high, variable" second7, third, low, warm, and off,

as well as an interlock mechanism that is responsive-to operation of anyone of the six pushbuttons intoits depressed position toetfect the returnof the last-operated oneof-thesix pushbuttons back into its normal projected position. Further, the heat setting switch 76 comprises.

four movable switch blades 84, 85, 36 and 87 that are selectively operatedby the-selectiveoperations of, the six pushbuttons mentioned.

movable switch blade 85 cooperates with respective back andfront-stationaryv switchblades S9 and the movable switch blade-86 cooperates with respectiveback and front: stationaryswitchblades 91 and 92; and the movable'switcha blade 87 cooperates with a back stationary switch blade 93. The movable switch blade 84 is commonly connected to the stationary switch blades 89 and 91; the movable switch blades 85, 86 and, 87 are-respectively connected to three outgoing terminals that are respectively connected to three conductors 94, 95 and 96; the stationary switch blades 88 and 9.0 are respectively connected to two-incoming terminals that are respectively connected to-two.

conductors 97 and 98; and the stationary switch-blades. 92' and 93 are commonly connected to a third incoming;

terminal that isconnected to, a conductor 99;

As illustrated in Figs; 3 and 9; when the offphshbutton of theswitch 76' occupies its operated position, the movable switch, blad s 84 and 87" respectively'disengage the: sta,- tionary switch blades 88yand 93, and, themovableswitch blades;-85and, 8,6.respectively engage the stationary switch. blades 89 and 91; as shown in Fig.,4,,when, the high-' variable pushbuttoniof theswitch-76Z occupies itsoperated posit1on, the movable; switch; blades, 84, 85 8,6; and; 87.;

The'rnovable switch blade 84. cooperates with afrontstationary switch blade88; therespectively engage the stationary switch blades 88, 89, 91 and 93; as shown in Fig. 5, when the second pushbutton of the switch 76 occupies its operated position, the movable switch blades 84, 85, 86 and 87 respectively engage the stationary switch blades 88, 89, 92 and 93; as shown in Fig. 6, when the third pushbutton of the switch 76 occupies its operated position, the movable switch blades 84, 85 and 86 respectively engage the stationary switch blades 88, 89 and 92 and the movable switch blade 87 disengages the stationary switch blade 93; as shown in Fig. 7, when the low pushbutton of the switch 76 occupies its operated position, the movable switch blade 84 disengages the stationary switch blade 88 and the movable switch blades 85, 86 and 87 respectively engage the stationary switch blades 90, 91 and 93; and as shown in Fig. 8, when the warm pushbutton of the switch 86 occupies its operated position, the movable switch blades 84 and 87 respectively disengage the stationary switch blades 88 and 93 and the movable switch blades 85 and 86 respectively engage the stationary switch blades 90 and 92. The heating rate control switch 77 comprises a first set of two movable contact springs 100 and 101 that is governed by a first rotatably mounted eccentric 102 and a second set of two movable contact springs 103 and 104 that is governed by a second rotatably mounted eccentric 105. Specifically the eccentric 102 is carried by an operating shaft 106 that is provided with a manually rotatable dial 107 that cooperates with an index marker 108; and the eccentric 105 is carried by an operating shaft 109 that is provided with a gear train 110 that is connected to the operating shaft 111 of a timer motor M2 of the synchro-' nous type. In the arrangement, when the timer motor M2 is energized, the operating shaft 111 governs the gear train 110 so that the operating shaft 109 is rotated at a speed of R. P. M.; whereby the eccentric 105 operates the movable contact springs 103 and 104 toward and away from the contact springs 100 and 101 at this rate. The normal position of the contact springs 100 and 101 is determined by the position of the eccentric 102 that, in turn, is determined by the adjusted position of the manual dial 107 that includes low, medium and high positions with respect to the index marker 108. Accordingly, in the operation of the heating rate control switch 77 the movable contact springs 103 and 104 are operated cyclically to engage and to disengage the movable contact springs 100 and 101; and in each cycle the percentage make-contact and the complementary percentage breakcontact is determined by the adjusted position of the manual dial 107 through the eccentric 102 that sets the riding of the movable contact springs 100 and 101 upon the movable contact springs 103 and 104. Specifically, the percentage make-contact may be adjusted from about 6% (with a complementary percentage break-contact of about 94%) to about 94% (with a complementary percentage break-contact of about 6%).

Further, the control circuit for the machine 20 comprises a three-wire Edison source of 236 volts, singlephase, A. C., including two ungrounded outside conductors 112 and 113 and a grounded neutral conductor 114-, a fuse link 115, and a transfer switch 116. The transfer switch 116 comprises a first movable switch blade 117 provided with back and front stationary switch blades 118 and 119, a second movable switch blade 120 provided with back and front stationary switch blades 121 and 122, and a third movable switch blade 123 provided with a front stationary switch blade 124. The switch 116 is of the electromagnetic operated type including an operating coil 125 of the marginal type; whereby the movable switch blades 117, 120 and 123 are operated from their rest positions into their operated positions only in response to energization of the operating coil 125 with a predetermined current, as explained more fully hereinafter. In the arrangement, when the transfer switch 116 occupies its rest position, the movable switch blade 117 engages the back stationary switch blade 118, the movable switch blade 120 engages the back stationary switch blade 121 and the movable switch blade .123 disengages the front stationary switch blade 124. When the transfer switch 116 occupies its operated position, the movable switch blade 117 engages the front stationary switch blade 119, the movable switch blade 120 engages the front stationary switch blade 122 and the movable switch blade 123 engages the front stationary switch blade 124.

In the circuit arrangement: the line conductor 112 is connected to the upper spring of the set S3, while the lower spring thereof is connected to a conductor 126; the line conductor 113 is connected to the upper spring of the set S4, while the lower spring thereof is connected to a conductor 127; the upper and lower springs of the set S1 are respectively connected to two conductors 128 and 129; and the upper spring of the set S2 is connected to a conductor 130, while the lower spring thereof is also connected to the conductor 127. The fuse link is bridged across the conductors 127 and 129; and the neutral line 114 is commonly connected to the upper back contact of the bridging member 74, to one terminal of the run winding 70, to one terminal of the timer motor M1, to one terminal of the solenoid 54a, to the conductor 98 and to one terminal of the timer motor M2. The lower back contact of the bridging member 74 is connected to a conductor 131 that, in turn, is connected to one terminal of the start winding 69; the other terminal of the run winding 70 and the other terminal of the start winding 69 are commonly connected to the conductor 129; and the other terminal of the timer motor Mi is connected to the conductor 127. The front contacts of the bridging member 73 are respectively connected to the conductors 126 and 97; while the front contacts of the bridging member 74 are respectively connected to the conductors 130 and 99. The other terminal of the solenoid 54a is connected to a conductor 132; the contacts of the bridging member 68 terminate the conductors 132 and 128; and the other terminal of the timer motor M2 is connected to a conductor 133. The conductors 94, 95 and 99 are also respectively connected to the switch blades 117, and 123; while the switch blades 118, 119, 121, 122 and 124 are respectively connected to conductors 134, 135, 136 and 137 and to the conductor 133. The conductor 134 is commonly connected to the switch springs 63 and 104; the conductor 135 is connected to the switch spring 101; the conductor 136 is commonly connected to the switch springs 64 and 1%; and the conductor 137 is connected to the switch spring 100. The operating coil of the transfer switch 116 is connected across the conductors 95 and 96; and the switch springs 65 and 66 are respectively connected to two conductors 138 and 139. The section 34a of the heating unit 34 is bridged across the conductors 96 and 139, while the section 34b of the heat ing unit 34 is bridged across the conductors 96 and 138; whereby the conductor 96 is connected to the midpoint between the sections 3411 and 3411.

Considering now the cycle of operation of the machine 2%, operation thereof is initiated when the manual dial 78 of the master timer switch 75 is rotated out of its off position into its variable on position, which corresponds to a time interval within twenty minutes, as indicated in the time sequence chart at the top of Fig. 3. When the manual dial 78 is thus operated out of its off position, rotation of the drum 22 is initiated to effect tumbling of the clothes, and energization of the heating unit 34 is determined in accordance with the position of the heat-setting switch 76. Entirely for purposes of description, it is first assumed that the heat-setting switch 76 occupies its off position so as to prevent energization of the heating unit 34; whereby in this case operation of the manual dial 78 of the master timer switch 75 out of its off position into its variable on" position causes the control cams C1 to C4, inclusive, to close the sets of switch springs S1 to S4, inclusive, so that the timer motor M1 is energized efiecting operation thereof and the consequent ultimate return of the manual dial 78 back into its .ofi position, as explained more fully hereinafter. Closure of the set of switch springs S4 also completes a circuit via the fuse link 115 for energizing in multiple the start and run windings 69 and 78 of the drive motor 41; whereby the drum 22 is rotated as previously explained. When the rotor 71 of the drive motor 41 is accelerated somewhat past its half normal running speed, the speed-responsive mechanism 72 operates the contact bridging members 73 and 74. Specifically, the contact bridging member 74 opens its back contacts to eifect deenergization of the start winding 69 of the drive motor 41; whereby the drive motor 41 is accelerated on into its normal running speed by the enrgization of the run winding 70 thereof. Specifically, the contact bridging member 73 at its front contacts connects the conductor 126 to the conductor 97, while the contact bridging member 74 at its front contacts connects the conductor 130 to the conductor 99; whereby the line-to-line voltage of the Edison source is applied to the conductors 97 and 99 extending to the heat-setting switch 76; however, without result at this time, as it is assumed that the heat-setting switch 76 occupies its off position. Also when the manual dial 78 or" the master timer switch 75 is operated out of its oil? position into its variable on position, a circuit is completed for energizing the solenoid 5 m; which circuit also includes the contact bridging member 63, the

ass nt;

of its 0135 position into its variable on position, as described above. In this case, in the heating portion of the cycle of the machine 20, the conductors 98 and 99' are respectively connected to the conductors 94 and 95, and the transfer switch 116 remains in its restored position; whereby a circuit is completed for energizing in series relation the two sections 34a and 34b of the heating unit 34 across the line conductor 113 and the neutral conductor 114 (118 volts) so that the heating unit that at a fixed time interval of 7 minutes preceding the operation of the master timer switch 75 back into its closed set of switch springs S1, the fuse link 115 and the during the time interval of operation of the master timer switch 75.

As time proceeds, the master timer switch 75 is operated from its variable on position into its fixed on position that may subtend 4-0 minutes, as indicated in the chart at the top of Fig. 3. Still subsequently, at a fixed time interval of 7 minutes preceding the operation of the master timer switch 75 back into its off position, the control cams C2 and C3 govern the sets of switch springs S2 and S3 to interrupt further points in the circuits extending to the heat-setting switch 76 so as to interrupt these circuits, described more fully hereinafter, for energizing the heating unit 34; which circuits are open in the heat-setting switch 7 6, in the present example. Still subsequently, at a fixed time interval of 1 /2 minutes preceding the operation of the master timer switch 75 back into its oil position, the control cam C1 governs the set of switch springs S1 to interrupt the circuit for energizing the solenoid 54a so that the inlet valve 54 is returned back into its closed position. to cut off the supply of cool water to the jet nozzle 56. Still subsequently, upon operation of the master switch 75 back into its off position, the control cam C4 governs the set of switch springs S4 to open the parallel circuits for operating the timer motor M1 and the drive motor 41; whereby operation of the master timer switch 75 is arrested while the manual dial 78 is in its oii position; and whereby operation of the drive motor 41 is arrested so as to arrest rotation of the drum 22 and the consequent tumbling of the clothes contained therein. Accordingly, at this time, the cycle of the machine is completed and the contained clothes in the drum 2.2 may be removed therefrom after opening of the associated front door, not shown.

Now assume that the heat-setting switch 76 occupies its warm position, as illustrated in Fig. 8, when the cycle of operation of the machine 20 is initiated by operation of the manual dial 78 of the master timer switch 75 out oii position the control cams C2 and C3 operate the set of switch springs S2 and S3 in their open positions so as to disconnect the line conductors 113 and 112 from the conductors 97 and 99 extending to the heat-setting switch 76 for the purpose of concluding the heating cycle of the heating unit 34 at this time.

Now assume that the heat-setting switch 76 occupies its low position, as illustrated in Fig. 7, when the cycle of operation of the machine 20 is initiated by operation of the manual dial 73 of the master timer switch 75 out of its off position into its variable on position, as described above. ln this case, in the heating portion of the cycle of the machine 29, the conductors 9S and 99 are respectively connected to the conductors 94 and 96 and the transfer switch 116 remains in its restored position; whereby a circuit is completed for energizing the section 34a of the heating unit 34 across the line conductor 113 and the neutral conductor 114 (118 volts) so that the heating unit generates heat at the low rate. This cycle of operation of the machine 29 is substantially identical to that previously described, and is not repeated in the interest of brevity.

Now assume that the heat-setting switch 76 occupies its third position, as illustrated in Fig. 6, when the cycle of operation of the machine 20 is initiated by operation of the manual dial 7 8 of the master timer switch 75 out of its off position into its variable on position, as described above. In this case, in the heating portion of the cycle of the machine 2t), the conductors 97 and 99 are respectively connected to the conductors 94 and 95 and the transfer switch 116 remains in its restored position; whereby a circuit is complete for energization in series relation the two sections 34a and 34b of the heating unit 34 across the line conductors 112 and 113 (236 volts) so that the heating unit 34 generates heat at the third rate. This cycle of operation of the machine 2t? is substantially identical to that previously described, and is not repeated in the interest of brevity.

Now assume that the heat-setting switch 76 occupies its second position, as illustrated in Fig. 5, when the cycle of operation of the machine 20 is initiated by operation of the manual dial 7 8 of the master timer switch 75 out of its off position into its variable on position, as described above. In this case, in the heating portion of the cycle of the machine 29, the . conductors 97 and 99 are respectively connected to the conductors 94 and 96 and the transfer switch 116 remains in its restored position; whereby a circuit is completed for energizing the section 34a of the heating unit 34 across the line conductors 112 and 113 (236 volts) so that the heating unit 34 generates heat at the second rate. This cycle of operation of the machine 20 is substantially identical to that previously described, and is not repeated in the interest of brevity.

Now assume that the heat-setting switch 76 occupies its high-variable position, as illustrated in Fig. 4, when the cycle of operation of the machine 20 is initiated by operation of the manual dial 78 of themaster timer switch 75 out of its off position into its variable on position, as described above. In this case, in the heating portion of the cycle of the machine 20, the conductor 7 is commonly connected to the conductors 94 and 95' 9 and the conductor 99 is connected to the conductor 96 and the transfer switch 116 is operated; whereby circuits are completed for energizing in parallel relation the sections 34a and 34b of the heating unit 34 across the line conductors 112 and 113 (236 volts) so that the heating unit 34 generates heat at the high variable rate and depending upon the further setting of the heating rate control switch 77, as explained below.

More particularly, when the conductors 95 and 96 are connected to the respective conductors 97 and 99 and the last-mentioned conductors are respectively connected to the line conductors 112 and 113, a circuit is completed for energizing the operating coil 125 of the transfer switch 116 across 236 volts, whereby the transfer switch 116 is operated from its rest position into its operated position since the operating coil 125 is of the marginal type and is responsive to the 236 volts impressed thereacross in this case. More particularly, the movable switch blades 117 and 120 are operated to disengage the respective stationary back switch blades 118 and 121 and to engage the respective front switch blades 119 and 122, and the movable switch blade 123 is operated to engage the front stationary switch blade 124. Accordingly, the conductors 94 and 95 are disconnected from the conductors 134 and 136 extending directly to the contact springs 63 and 64 and are respectively connected to the movable contact springs 101 and 100; while closure of the switch blades 123 and 124 completes a circuit for operating the timer motor M2 of the heating rate control switch 77. The operating timer motor M2 drives the eccentric 105 at a speed of 5 R. P. M. through the elements 111, 110 and 109 so that the movable switch springs 103 and 104 respectively engage and disengage the movable switch springs 100 and 101 five times per minute. When the movable switch springs 103 and 104 are in engagement with the movable switch springs 100 and 101, the conductors 137 and 135 are connected to the respective conductors 136 and 134 and thus to the switch springs 64 and 63 of the thermal cutout switch 60, thereby completing the previously-mentioned circuit for energizing in parallel relation the two sections 34a and 34b of the heating unit 34 across the line conductors 112 and 113 of the Edison source.

Now in each of the five cycles per minute of the heating rate control switch 77, the ratio between the percentage make-contact and the percentage break-contact is determined by the adjusted position of the movable switch springs 100 and 101 that, in turn, is determined by the adjusted position of the manual dial 107 cooperating with the index marker 108. When the manual dial 107 occupies its low position illustrated, it may be assumed that the percentage make is 6% in each cycle of the switch 77; and when the manual dial 107 occupies its high position, it may be assumed that the percentage make is 94% in each cycle of the switch 77. The heating rate control switch 77 is of the so-called infinitely adjustable type; whereby any percentage-make contact between the 6% and the 94% may be effected by a corresponding rotary adjustment of the manual dial 107 with respect to the index marker 108.

Accordingly, it will be understood that when the heatsetting switch 76 occupies its high-variable position, the actual heating rate of the heating unit 34 is adjustable over an exceedingly wide range depending upon the setting of the heating rate control switch 77 that is effected by the manual adjustment of the dial 107. In fact, this heating rate may be adjusted from a rate disposed well below the fixed warm rate (when the heatsetting switch 76 is in its warm position of Fig. 8) to a rate disposed Well above the fixed second rate (when the heat-setting switch 76 is in its second position of Fig. 5).

In this case, when the heat-setting switch 76 occupies its high-variable position, energization of the heating unit 34 continues on a cyclic basis under the control of the heating rate control switch 77 until the master timer switch 75 is operated into its fixed position disposed 7 minutes preceding its off position; whereby the control cams C2 and C3 operate the sets of switch springs S2 and S3 to disconnect the line conductors 113 and 112 from the conductors 99 and 97, thereby to deenergize the operating coil 125 of the transfer switch 116 causing the transfer switch 116 to be returned from its operated position back into its restored position. When the transfer switch 116 is thus returned back into its restored position, the movable switch blade 123 disengages the front stationary switch blade 124 so as to interrupt the circuit for operating the timer motor M2 of the heating rate control switch 77. Also the movable switch blades 117 and 120 re-engage the back stationary switch blades 118 and 121 so as to reprepare the previously traced normal rest circuits for energizing the heating unit 34.

In view of the foregoing description of the heating cycle of the heating unit 34 incorporated in the machine 20, it will he understood that the same is deenergized when the heat-setting switch 76 occupies its off position, that the same is energized at corresponding fixed heating rates when the heat-setting switch 76 occupies its warm, low, third and second positions, and that the same is energized at a variable heating rate when the heat-setting switch 76 occupies its high-variable position, and as determined by the adjustment of the heating rate control switch 77 in this case. Also in the high-variable position of the heat-setting switch 76, the energization of the heating unit 34 is not only variable, but is also cyclic, by virtue of the cyclic operation of the heating rate control switch 77.

The cyclic energization of the heating unit 34 under the control of the heating rate control switch 77 when the heat-setting switch 76 occupies its high-variable position is generally as indicated by the curves B1B2 in Fig. 10 by virtue of the fact that the swing of the temperature in the drum 22 above and below the desired temperature is greatly minimized with respect to that of a conventional thermostatically controlled machine. Referring to Fig. 10, it is noted that in a conventional thermostatically controlled .clothes drying machine of this character, the temperature within the rotating drum 22 is indicated by the curves A1-A2; when the thermostatically controlled switch is set at a desired temperature T. Specifically, in the normal cycle of operation of such a conventional thermostatically controlled machine, the cycle of the thermostatic switch may be in the general range: 5 to 10 minutes, after the desired temperature has been reached; whereby the temperature Within the rotating drum 22 normally rises about 15 F. above the desired temperature T and then falls about 15 F. below the desired temperature T as indicated by the curve A2. Now in this temperature cycle, as indicated by the curve A2, the high temperature may rise above the damaged temperature of delicate fabrics made of synthetic mate-' rials (nylon, etc. fibers); while the low temperature may fall below the eifective temperature of the clothes drying function. Accordingly, as indicated by the curve A2 in such a. conventional thermostatically controlled clothes drying machine, the useful temperature within the rotating drum 22 is maintained only during a fraction of the cycle of the thermostatically controlled switch.

On the other hand, as illustrated by the curve B2 of the present clothes drying machine 20, the temperature in the rotating drum 22 never varies more than about 1 F. from the preset desired temperature, as established by the setting of the heating rate control switch 77 when the heat-setting switch 76 occupies its high-variable position. This circumstance flows from the fact that the heating unit 34 is cyclically energized and deenergized five times per minute (every 12 seconds). Accordingly, in the present arrangement, the desired temperature in the rotating drum 22 may be accurately set by the heat rate control switch 77, when the heat-setting switch 76 occupies its high-variable position; thereby eliminating the sees e415 11 usual inherent overshoot and undershoot temperature characteristics of thermostatically controlled switching equipment that is conventionally incorporated in clothes drying machines of the home laundry type.

In view of the foregoing, it is apparent that there has been provided in a clothes drying machine of the home laundry type, a control circuit of improved and exceedingly flexible connection and arrangement.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a clothes drying machine including a drum mounted for rotation about a substantially horizontal axis and adapted to receive and to tumble the clothes to be dried, an electric motor operative to rotate said drum, and an electric heating unit for evaporating moisture from the clothes in said drum; the electric control circuit combination comprising a source of electric power, a manually operable control switch having a plurality of control positions respectively corresponding to a plurality of heating rates of said heating unit, said control switch in its plurality of control positions respectively establishing a corresponding plurality of heating connections between said power source and said heating unit, a cycle switch included in one of said heating connections for opening and for closing in each cycle thereof said one heating connection, a manually operable device for selectively setting the ratio between the open contact time and the closed contact time of said cycle switch in each cycle thereof, thereby selectively to vary the corresponding one heating rate of said heating unit during heating thereof in said one heating connection, a master switch selectively operative to control operation of said motor from said power source and to govern opening and closing of the established one of said heating connections, and manuall'y settable timing means for selectively operating said master switch.

2. The clothes drying machine electric control circuit combination set forth in claim 1, wherein said control switch' is of the pushbutton type comprising a number of individual pushbuttons respectively corresponding to the-different control positions thereof.

3.-In a clothes drying machine includinga drum mounted for rotation about a substantially horizontal axis and adapted to receive and to tumble the clothes to be dried, a three-wire Edison source of electric power, an electric motor operative to rotate said drum, and a twosection electric heating unit for evaporating moisture from the clothes in said drum; the electric control circuit combination comprising a manually operable control switch having a plurality of control positions respectively corresponding to a plurality of heating rates for said heating unit, said control switch in its plurality of control positions respectively establishing a corresponding plurality of heating connections between said power source and said heating unit, said plurality of heating connections respectively including ditferent combinations of two of the three conductors of said power source and different series and parallel arrangements of the two sections of said heating unit, a cycle switch included in one of said heating connections for opening and for closing in each cycle thereof said one heating connection, a manually operable device for selectively setting the ratio between the open contact time and the closed contact time of said cycle switch in each cycle thereof, thereby selectively to vary the corresponding one heating rate of said heating unit during heating thereof in said one heating connec tion, a master switch selectively operative to control operation of said motor from said power source and to govern'opening and closing of the established one of said heating connections, and manually settable timing means for selectively operating said master switch.

7 4. In a clothes drying machine including a drum mounted for rotation about a substantially horizontal axis and adapted to receive and to tumble the clothes to be dried, an electric motor operative to rotate said drum, and an electric heating unit for evaporating moisture from the clothes in said drum; the electric control circuit combination comprising a source of electric power, a heating circuit extending from said power source to said heating unit and including first and second series related switch points, a cycle switch operative to open and to close in each cycle of operation thereof said first switch point, a master switch selectively operative to control operation of said motor from said source and to govern opening and closing of said second switch point and to control operation of said cycle switch, manually settable timing means for selectively operating said master switch, and a manually operable device for selectively setting the ratio between the open contact time and the closed contact time of said cycle switch in each cycle of operation thereof, thereby selectively to establish the effective heating rate of said heating unit during heating thereof in said heating circuit.

, 5. The clothes drying machine electric control circuit combination set forth in claim 4, wherein the cycle of operation of said cycle switch is of a time duration of only a fraction of a minute.

6. The clothes drying machine electric control circuit combination set forth in claim 4, wherein the range of the ratio between the open contact time and the closed contact time of said cycle switch in each cycle of opera-.

tion thereof is of the order of 1:N at one end thereof and N21 at the other end thereof, where N is in the range 2 to 10. I

7. In a clothes drying machine including a drum mounted for rotation about a substantially horizontal axis and adapted to receive and to tumble the clothes to be dried, an electric motor operative to rotate said drum, and an electric heating unit for evaporating moisture from the clothes in said drum; the electric control circuit combination comprising a source of electric power, a heating circuit extending from said power source to said heating unit and including first and second series related switch points, a cycle switch operative to open and to close in each cycle of operation thereof said first switch point, an electric timer operative to operate said cycle switch, a master switch selectively operative to control operation of said motor from said power source and to govern the opening and closing of said second switch point and to control operation of said electric timer from said power source, manually settable timing means for selectively operating said master switch, and a manually operable device for selectively setting the ratio between the open contact time and the closed contact time of said cycle switch in each cycle of operation thereof, thereby selectively to establish the effective heating rate of said heating unit during heating thereof in said heating circuit.

8. In a clothes drying machine including a drum mounted for rotation about a substantially horizontal axis and adapted to receive and to tumble the clothes to be dried, an electric motor operative to rotate said drum, and an electric heating unit for evaporating moisture from the clothes in said drum; the electric control circuit combination comprising a source of electric power, a manually operable control switch having a plurality of control positions respectively corresponding to a plurality of heating rates of said heating unit, said control switch in its plurality of control positions respectively establishing a corresponding plurality of heating connections between said power source and said heating unit, a master switch selectively operative to control operation of said motor from said power source and to govern opening and closing of the established one of said heating connections, a manually settable timer for selectively operating said master switch, a cycle switch included in one of said heating connections and operative to open and to close in each cycle of operation thereof said one heating connection, means responsive to operation of said control switch into its one control position establishing said one heating connection for causing said master switch also to control operation of said cycle switch, and a manually operable device for selectively setting the ratio between the open contact time and the closed contact time of said cycle switch in each cycle of operation thereof, thereby selectively to vary the corresponding one heating rate if said heating unit during heating thereof in said one heating connection.

9. In an electric heating system including a source of electric power, and an electric heating unit; the combination comprising a plurality of heating connections extending between said power source and said heating unit and respectively corresponding to a plurality of heating rates of said heating unit, a manually operable control switch having an oil position and a plurality of control positions respectively corresponding to said plurality of heating connections, said control switch being operative in its off position to open each of said heating connections and selectively operatix e into its control positions selectively to close said heating connections, a cycle switch included in one of said heating connections and operative to open and to close in each cycle of operation thereof said one heating connection, an electric motor for operating said cycle switch, means responsive to operation of said control switch into its one control position to close said one heating connection for operating said motor from said power source, and a manually operable device for selectively setting the ratio between the open contact time and the closed contact time of said cycle switch in each .le of operation thereof, thereby selectively to vary the corresponding one heating rate of said heating unit during heating thereof in said one heating connection.

10. The electric heating system combination set forth in claim 9, wherein said control switch is of the pushbutton type comprising a number of individual pushbuttons respectively corresponding to the different control positions thereof.

References Cited in the file of this patent UNlTED STATES PATENTS

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