US3096972A - Gas driers - Google Patents

Description

July 9, 1963 G. H. MITCHELL GAS DRIERS Filed Dec. 5. 1 960 5 Sheets$heet 1 Inventor LEONARD G. H. MITCHELL Attorney July9, 1963 L. G. H. MITCHELL 3,096,972

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Inventor LEONARD G. H. MITCHELL by: AQMVA Aftorne y United States Patent 01 3,096,972 GAS DRIERS Leonard G. H. Mitchell, Toronto, Ontario, Canada, assignor to General Steel Wares Limited, Toronto, Ontario, Canada Filed Dec. 5, 1960, Ser. No. 73,619 Claims. (Cl. 263-33) This invention relates to clothes driers and more particularly to a gas fired clothes drier.

The principal object of the invention is to provlde a gas fired clothes drier which will be extremely 'efficient and extremely safe in operation.

In particular, it is an important object to provide for an almost instantaneous detection of a change in normal flame pattern indicating improper drier operation and to provide for burner shut-off the instant that the abnormal flame pattern is detected to eliminate fire hazard.

Another important object is to further provide for an almost instantaneous detection of an abnormal temperature rise within the drier drum and to shut off the burner before damage to the clothing can occur.

Still another object is to provide a drier as aforesaid, the cabinet of which will remain cool even directly above the flame area.

Because of the problem of lint gathering at various parts of a clothes drier, particularly if the lint filter is not frequently cleaned, and because of the nature of the clothing itself, particularly clothing which may be highly inflammable, it has been considered necessary to remove the open gas flame to a point a substantial distance from the inlet to the drier drum. This conventional arrangement has meant that the drying air which is caused to pass through the drum must be led a substantially distance before entering the drum. As a result, considerable cooling of the air takes place as heat is given up to the walls of the conducting channel impairing the efliciency of the drier.

According to the present invention there is provided a novel folded air path arrangement leading into the drum, and the drying air that passes through the drum comprises high temperature air that passes through and is directly heated by the flame and enters the drum through the folded path, and a volume of air that bypasses but is indirectly heated by the flame, the arrangement being such that although a large volume of drying air is delivered into the drum the flame is enabled to be brought close to the drum entrance without danger of the flame being pulled out to enter the drum and ignite clothing or lint deposits in the drum.

-A further important feature resides in dividing the indirectly heated drying air between a first minor volume that flows past and is separated from the flame by a thin heat transfer surface, and a second major volume indirectly heated by the flame and the said minor volume, the said minor volume acting as a coolant for the heat trans.- fer surface as it passes thereover to pick up heat after which it is led to join the directly heated air in the folded air path.

In normal drier operation it will be understood that the flame will assume a substantially constant pattern being pulled downstream by the flow of directly heated drying air, and further according to the invention there is provided a temperature responsive device for effecting gas cut-off upon any substantial flame pattern deviation.

In this connection according to the invention the temperature responsive device is arranged immediately above the aforementioned heat transfer surface and slightly downstream of the gas burner to receive heat from said ice surface and to be contacted by the first minor volume of indirectly heated drying air passing over the surface.

A further feature resides in providing in connection with the flame pattern detector a further temperature responsive element to effect gas cut-01f upon abnormal temperature rise in the drum.

These and other objects and features of the invention will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective, exploded view, partly broken away, of a drier embodying the invention, portions of the drier being omitted for sake of clarity;

FIGURE 2 is a rear elevational view of the drier with the rear wall of the casing cut away;

FIGURE 3 is a side elevational view of the drier with a portion of the casing broken away;

FIGURE 4 is an enlarged exploded perspective view of the housing components defining the air flow path leading into the drum, taken from the rear of the machine;

FIGURE 5 is a perspective view of the burner employed in the drier;

FIGURE 6 is an enlarged, fragmentary, vertical sectional view illustrating the folded air path and the flame pattern detector, looking from the rear of the machine;

FIGURE 7 is a schematic Wiring diagram of the control circuit of the drier.

Referring first to FIGURES 1 to 3, the drier comprises a rectangular base frame 1 from which extends an upright post 2 having journalled in the upper end thereof a shaft 3 on which is rotatably supported a drying drum 4 having an end wall formation 5 carrying a journal block 6 receiving the shaft 3 and a perforated peripheral wall 7 which may be formed from a punched sheet, screening or other suitable foraminous material. A motor 8 mounted on a spring-loaded bracket 9 drives a fan 10 through a belt 11, the belt passing over a large pulley 12 which is floatingly mounted on a pivoted bracket 13 carrying a shaft 14 passing through the pulley. Shaft 14 carries a relatively smaller pulley 15 which drives through a belt 16 a relatively larger pulley 17 mounted on the drum shaft 3, the pulleys 12, 15 and 17 and belt drives 11 and 16 forming a reduction drive to the drum.

Tension is maintained on the belt drives 11 and 16 by means of the springs 18 and 19 respectively.

Surrounding the drum 4 is a housing 20 which is provided adjacent to the top with an inlet opening 21 defined in a section 2.2 of the housing formed from a suitable high heat-resistant material. Preferably a perforated plate or screen 23 covers the inlet and the inlet is divided as shown particularly in FIGURE 4 by means of a strip of suitable heat-resistant material 24. Adjacent to the bottom and preferably substantially diametrically opposite to the inlet 21, the housing 20 is provided with outlet openings 25 which are arranged to open into a conduit member 26 which leads to the [fan 10, there being provided a suitable removable lint filter member 27 adapted to be sleeved into and out of the conduit 26.

The operation of the fan 10' is such that it is arranged to draw air through the inlet 21 in the drum housing 20 into and across the drying drum 4 and out the housing outlets 25 through the lint filter 27, the filtered air being discharged either through the exhaust 23 at the rear of the machine, FIGURE 2, or the fan may be arranged to exhaust through the front of the machine through the exhaust 28, FIGURE 1.

Mounted on top of the section 22 of the drum housing 20 is an inner generally triangular shaped housing generally designated at 29, as shown in FIGURE 4, which has an inner baflle '30, as shown in FIGURE 6, that extends upwardly from the housing 20 at one side of the inlet opening '21 and then extends laterally across the opening to terminate centrally of the width of the imperforate strip 24 extending across the drum inlet. The outer wall 31 of the housing 29 defines with the baflie 30, a vertical inlet passage 32a, a tapering transverse passage 32b, and a vertical passage 32c terminating at the strip 24. In turn, the strip 24 and the baflie 3t} define a return path 32d which opens into the drum through the casing inlet 21 beneath the baflle 30. Thus the air flow path 32a to 32b comprises, as seen, a folded air flow path leading into the drum.

Spaced above the baflie 36 Within the housing 2? is a thin, heat transfer plate 33 which defines with the outer housing wall 31 a by-pass air flow path 33a which joins the folded air flow path at a point above the strip 24.

Overlying the housing '29 is a similarly shaped and slightly larger housing 34 which defines with the housing 29 an air flow by-pass 35 that completely surrounds the inner housing 29 and opens into the drum 4 through the housing inlet 21 at the side of the strip 24 opposite to that through which the air flowing in the folded air path 32a to 3212 enters.

Air flowing in the paths 32a to 32d, 33a and 35, is heated by means of a gas burner designated at 36 in FIG- URE which projects into the inner housing 29 through a suitable opening 37, the burner extending in a direction parallel to the drum axis through the vertical portion 32a of the folded air flow path.

As seen in FIGURE 4, the inner housing 29 is provided with depending bent-out lugs 38 which are adapted to enter punched up retaining bosses 3 9 in the housing section 22, and the housing section 22 is provided with upstanding perforated ears 40- adapted to register with corresponding openings 41 in the outer housing '34 for the reception of suitable fasteners, and the gas burner 36 is provided with a suitable mounting bracket 42 for attachment to the housing 29.

With reference to FIGURES 2 and 7, gas is arranged to enter the drier through an inlet manually controlled cock 43', FIGURE 2, and is delivered through suitable solenoid controlled valves generally designated at 44, through a gas line 46 to the pilot 72, FIGURE 7, and through the main gas line 45 to the burner 36, the control and sequence of gas flow operation being more fully explained inconnection with FIGURE 7.

The drier drum and its surrounding housing 20 and the housings 29 and M defining the air inlet flow path arrangement and the motor and blower and other components are all contained within a suitable casing 48, and to provide for the introduction and removal of the clothing, thedrum 4, housing 20, and casing 48, are arranged to define a circular entrance 4-9 leading into the drum and closed bya suitable door 50.

In the drying of clothes, it is usually desirable to provide a timer, generally designated at 51 in FIGURE 7, to select the time of operation of the drier, and an adjustable thermostat 52 to select the temperature at which the drier is to operate, the adjustable thermostat being set to turn the source of heat for the drying air on and off as the temperature within the drum reaches a pre-selected low temperature and high temperature point respectively. As in the usual case, the drier is provided with a temperature responsive element 53 arranged on the housing 20 to respond to abnormal temperatures in the drum and shut offthe heat energy source. According to the present invention, however, there is provided in addition a flame pattern detector 54 which comprises a temperature responsive device mounted in a well 5 in the outer housing 34 and projecting through an opening 56 in the inner housing 29, so that its temperature responsive element lies immediately above the heat transfer plate 33 and slightly downstream with respect to the burner 66.

When the burner 36 is operating, the primary air for supporting the combustion of the gas escaping through the series of gas ports 57 is provided through the dampered controlled primary air inlets 58 at the rear of the burner, as shown particularly FIGURE 5, and the air flowing through the air passages 32a and 3212 will provide the necessary secondary air to afford complete combustion of the gas and as well, a quantity of drying air which passes through and is directly heated by the flame on its way through the folded air flow path into the drum to eflect a draw-out of the flame to give the flame pattern 59 as show nin solid lines in FIGURE 6. It will be noted that the burner and flame are displaced from the inlet 21 to the drum around a bend in the folded airpath as defined by the free end of the inner baflle 30.

In addition to the directly heated drying air that passes through the flame, it will be understood that there will be a small Volume of indirectly heated air flowing over the heat transfer plate 33 land through the flow path 33a to rejoin the directly heated drying air in the latter portion of the folded air path. The air flowingin the path33a will pick up the heat from the heat transfer plate 33 and in so doing will serve as a coolant for the flame pattern detector 54. The drying air passing directly through the flame 59 will, of course, be the highest temperature air entering the drum, but the air flowing through the path 3311 will also be relatively high temperature air. In addition, air will be drawn into the drum through the air flow path 35 surrounding the inner housing '29. This air will be heated indirectly by the flame and by the air flowing through the path 33a and will be maintained separate from the directly heated air flowing through the folded air path. The air flow through the path 35- 'will serve as a further coolant to the flame pattern detector and will also act as an insulating barrier to the transfer of heat directly up to the main casing 48 so that the drier will be cool on the outside. Further by having a portion of the drying air by-passing the flame, the drawout of the flame will be minimized and by the provision of this by-pass arrangement, coupled with the folded air path for the directly heated drying air, the flame can be brought relatively close to the entrance of the drum so that the heat of the drying air is not dissipated in the drier casing and air flow path before entering the drum. While the air entering the drum through the path 35 will not be at the same high temperature [as the directly heated air, it will nevertheless have appreciable drying capacity and will have substantial volume flow.

As will be seen from FIGURE 6, should there be any deviation in the pattern of the flame 59, such as to reduce its pull-out, the flame will move to provide a flame pattern and occupy the dotted position shown at 60. This will bring the flame substantially immediately under the flame pattern detector 54 which is arranged to open circuit the control circuit of FIGURE 7 upon detecting any abnormal temperature rise.

It will be appreciated that any one of a number of conditions which would give rise to dangerous drier operation will effect the shift of the flame pattern from the solid line showing of '59 to the dotted line showing of 60. For example, if the fan should fail to operate, or if the lint filter becomes plugged, the air flow through the drier will be stopped or reduced and immediately the flame will move back to contact the heat transfer plate substantially beneath the flame pattern detector. Further, the reduced air flow will reduce the flow of cooling air through the passage 3302, so that not only is there the application of the flame almost directly onto the flame pattern detector, but the coolant for the flame pattern detector is reduced or removed. As a result, it has been found that the flame pattern detector responds almost instantaneously to flame pattern changes reducing flame pull-out, and as explained in further detail in connection with FIGURE 7, the operation of the flame pattern detector is to cut off gas flow.

With reference to FIGURE 7, the electrical control circuit is fed from the line through a suitable plug-in connector 61 which delivers current to the timer 51 comprised by the timer motor 62 and the timer control mechanism 63 for setting the time of drying, and to the main motor 8 for driving the drum in rotation. Preferably, the circuit is provided with a circuit breaker 64 and a door switch 65 which, with the door closed, occupies the solid line position shown to energize the control circuit. When the door is open, switch 65 will occupy the dotted line position to apply voltage to a lamp 66 which is arranged to shine into the interior of the drum 4 for lighting purposes. Current to the solenoids of the valves 44 is delivered through the temperature responsive element '53 and the flame pattern detector 54 arranged in series with the devices 53 and 54 being of the type having normally closed contacts until subjected to temperatures above desired pre-selected temperature limits.

From the flame pattern detector 54, current is delivered to a warp switch 67 which is adapted to remain closed While subjected to the heat from a heater 68' for a given period, but upon heat being continued to be directed at the switch, the switch is adapted to open and remain open for a given period.

From the warp switch 67, current is delivered through its normally closed contacts to a transformer 69 which is arranged to energize a glow coil 70. In addition current flow is delivered through the normally closed contacts of the warp switch to the pilot valve solenoid 71 to open the valve and provide gas flow to the pilot 72. A further current path in series with the closed contacts of the warp switch leads through the adjustable thermostat 52 and solenoid 73 for opening the main gas valve, but this circuit remains open with respect to the return line 74- through the hot con-tact H of the pilot detector plug-in unit 75 which incorporates a switch contact 76 movable from a position to which it is urged to return in contact with the cold contact C to a position contacting the hot contact H. As will be seen, with the switch contact 76 occupying its normal position in contact with the contact C, the transformer 69 is connected to a return line 74 returning to the connector 61.

The pilot 72, when lit, is arranged to heat an expanding material, such as mercury, in a tube 77, and when expanded, the mercury is adapted to operate a plunger 78 to actuate the switch contact 76 to break its connection with contact C and to make connection with the contact H to energize the main gas flow solenoid 73 to allow gas flow to the burner 36.

Thus, when the drier is first turned on, current flow is delivered through the closed contacts of the wrap switch 67 to the transformer 69 which is coupled to the return circuit through the switch contact 76 in contact with the cold contact C of the plug-in unit 75. This connection lights the glow coil 70. At the same time, the circuit is made through the pilot valve solenoid 71 to turn on the gas to the pilot 72 and this gas will be ignited by the glow coil 70.

As soon as the mercury in the tube 77 is heated so that the plunger 7 8 is actuated to move switch contact 76 from the cold contact C to the hot contact H, the main solenoid 73 will be energized to open the main valve and allow gas into the burner where it will be ignited.

When the switch contact 76 is operated to move it from contact with the cold contact C to the hot contact H, the pilot solenoid 71 will remain energized and the pilot will remain on, but the transformer 69 and the heater 68 will be de-energized saving burning out of the glow coil and preventing suflicient heat build up on the contacts of the warp switch 67 to open the switch.

It will be appreciated that should either of the temperature responsive element 53 or flame pattern detector 54 open circuit due to abnormal temperature rises, current to the warp switch 67 will be interrupted cutting off current flow to the heater 68, transformer 69 and solenoids 71 and 73, de-energizing the glow coil and closing the gas valves to cut off gas flow to the pilot and burner.

The adjustable thermostat 52 is arranged in series with the main gas valve solenoid 73 so that as it cuts on and off as it reaches its temperature limits, gas flow to the burner will be cut on and off, but the pilot will continue to operate.

Should gas flow not reach the pilot 72 for any reason whatsoever, the switch contact 76 of the plug-in unit 75 will remain closed against contact C and heater 68 will be continued to be energized through this contact which connects back to the return line 74 and the glow coil will be continued to be energized. It will be understood that in due course the heat trom the heater 68 will build up sufficiently to open the contacts of the warp switch 67 dc-energizing the entire circuit until the warp switch becomes re-set as for instance by a lapse of time.

To avoid variations in the flame pattern due to changes in pressure in the gas source, there is preferably provided a suitable pressure regulator 79 maintaining uniform gas pressure to the burner 36.

It will be understood that a drier as described will operate safely with positive controls to ensure gas shut off upon any abnormal condition being set up in the drier, and at the same time, when operating, there will be a substantial flow of both high temperature directly heat drying air and lower temperature indirectly heated air to provide a rapid rate of drying. Further, it will be seen that through the use of the outer casing 34, substantially all heat will be retained and delivered into the drier allowing the drier to remain cool on the outside and augmenting the drying capacity from a given heat source.

While the preferred embodiment of the invention has been illustrated and described, it Will be understood that variations in details and the arrangement of parts and other modifications as may be apparent to those skilled in the art may be made without departing from the spirit of the invention or scope of the appended claims.

What I claim is:

1. In a gas drier of the type comprising a perforated drum rotatably mounted in a housing having an inlet for heated drying air, and an outlet for moisture laden air and positive air circulating means for causing air to enter said drum through said housing inlet and exhaust from said drum through said housing outlet, means defining a folded air path leading into said housing inlet, gas burner means for producing an open flame in said folded air path and separated from said housing inlet by a reverse fold in said path requiring air passing through said flame to reverse flow direction through substantially in said flow path to reach said housing inlet, means dividing air flow into said housing inlet into directly heated drying air passing through said flame and indirectly heated drying air heated by but bypassing said flame, means to divide said indirectly heated drying air between a first minor air flow stream separated from the open burner flame by a thin heat transfer wall and a second major air flow stream isolated from the "burner flame by said minor secondary air flow stream, and a flame pattern detector located dovmstream of said gas burner in said folded air path and disposed and arranged to cut oil gas flow upon appreciable flame pattern change, said flame pattern detector comp-rising a thermal responsive device disposed substantially in contact with said heat transfer wall and exposed to said minor air flow stream of indirectly heated air.

2. A gas drier as claimed in claim 1 in which said thermal responsive device is disposed above and slightly downstream towards the housing inlet with respect to said burner.

3. A gas drier as claimed in claim 1 in which gas flow to said burner is controlled by a solenoid operated valve and said thermal responsive device is connected to control the solenoid of said valve to shut off gas flow to said burner upon abnormal temperature rise in said thermal responsive device.

4. A gas drier as claimed in claim 3 in which said burner is a pilot operated burner and gas flow to the pilot of said burner is controlled by a solenoid operated valve and said thermal responsive device is connected to control the solenoid of said latter valve to shut off pilot gas flow upon abnormal temperature rise in said thermal responsive device.

5. In a gas drier, a rotatable drum, means defining a fielded air flow path presenting a reverse fold and leading into said drum, burner means producing a flame for heating air flowing in said folded air path, means defining a flow path encompassing and by-passing said folded air flow path, and flame pattern detector means responsive to flame patterns in said folded path for controlling said heating means located in said flow path encompassing and by-passing said folded air flow path and downstream of said heating means.

References Cited in the file of this patent UNITED STATES PATENTS 1,848,150 Becker Mar. 8, 1932 2,194,713 Mitchell Mar. 26, 1940 2,867,430 Hull-a1 Jan. 6, 1959 2,919,750 Cobb Jan. 5, 1960 2,931,687 Mitter Apr. 5, 1960 2,958,140 Smith NOV. 1, 1960 i FOREIGN PATENTS 133,505 Great Britain Oct. 16, 1919

Claims (1)

1. IN A GAS DRIER OF THE TYPE COMPRISING A PERFORATED DRUM ROTATABLY MOUNTED IN A HOUSING HAVING AN INLET FOR HEATED DRYING AIR, AND AN OUTLET FOR MOISTURE LADEN AIR AND POSITIVE AIR CIRCULATING MEANS FOAR CAUSING AIR TO ENTER SAID DRUM THROUGH SAID HOUSING INLET AND EXHAUST FROM SAID DRUM THROUGH SAID HOUSING OUTLET, MEANS DEFINING A FOLDED AIR PATH LEADING INTO SAID HOUSING INLET, GAS BURNER MEANS FOR PRODUCING AN OPEN FLAME IN SAID FOLDED AIR PATH AND SEPARATED FROM SAID HOUSING INLET BY A REVERSE FOLD IN SAID PATH REQUIRING AIR PASSING THROUGH SAID FLAME TO REVERSE FLOW DIRECTION THROUGH SUBSTANTIALLY 180* IN SAID FLOW PATH TO REACH SAID HOUSING INLET, MEANS DIVIDING AIR FLOW INTO SAID HOUSING INLET INTO DIRECTLY HEATED DRYING AIR PASSING THROUGH SAID FLAME AND INDIRECTLY HEATED DRYING AIR HEATED BY BUT BYPASSING SAID FLAME, MEANS TO DIVIDE SAID INDIRECTLY HEATED DRYING AIR BETWEEN A FIRST MINOR AIR FLOW STREAM SEPARATED FROM THE OPEN BURNER FLAME BY A THIN HEAT TRANSFER WALL AND A SECOND MAJOR AIR FLOW STREAM ISOLATED FROM THE BURNER FLAME BY SAID MINOR SECONDARY AIR FLOW STREAM, AND A FLAME PATTERN DETECTOR LOCATED DOWNSTREAM OF SAID GAS BURNER IN SAID FOLDED AIR PATH AND DISPOSED AND ARRANGED TO CUT OFF GAS FLOW UPON APPRECIABLE FLAME PATTERN CHANGE, SAID FLAME PATTERN DETECTOR COMPRISING A THERMAL RESPONSIVE DEVICE DISPOSED SUBSTANTIALLY IN CONTACT WITH SAID HEAT TRANSFER WALL AND EXPOSED TO SAID MINOR AIR FLOW STREAM OF INDIRECTLY HEATED AIR.

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