US3541303A

US3541303A - Lint collecting and burning screen

Info

Publication number: US3541303A
Application number: US681325A
Authority: US
Inventors: Thomas J Brinkman; Thomas H Fogt; Charles C Whistler Jr
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1967-11-08
Filing date: 1967-11-08
Publication date: 1970-11-17
Anticipated expiration: 1987-11-17

Description

Ndv. 17, 1970 BRlNKMAN EIAL 3,541,303

LINT COLLECTING AND BURNING SCREEN Filed Nov. 8. 1967 I 2 Sheets-Sheet 1 g' INVENTORS 12 Y Charles Whi /mill? ATTORNEY 1970 'r. J. BRINKMAN ETAL 3,541,303

LINT COLLECTING AND BURNING SCREEN Nov.

2 Sheets-Sheet 2 Filed Nov. 8. 1967 United States Patent LINT COLLECTING AND BURNING SCREEN Thomas J. Brinkman, Dayton, Thomas H. Fogt, West Carrollton, and Charles C. Whistler, Jr., Dayton, Ohio,

assignors to General Motors Corporation, Detroit,

Mich., a corporation of Delaware Filed Nov. 8, 1967, Ser. No. 681,325 Int. Cl. Hb 3/10 U.S. Cl. 219-374 13 Claims ABSTRACT OF THE DISCLOSURE This invention relates generally to lint collecting and burning screens and more particularly to a directly energized screen for collecting and burning lint.

The disposal of lint accumulated from clothes being dried in a dryer by burning it within the dryer is not new. In fact, the concept of directly energizing the lint collecting screen to burn the lint entrapped on it is not new. However, so far as we are aware, no present directly energized lint burning screen has been directed to solving the problem of drawing a large amount of current with the attendant problem of materially reducing the voltage source somewhere within the dryer by the inclusion of a step-down transformer, usually with a high voltage ratio.

Accordingly, the object of this invention in one of its broadest aspects is to provide a directly energized lint burning screen which draws appreciably less current than those now available, or stated another way, which oifers more resistance than those now available.

Another object of our invention is to provide such a lint burning screen in which the pore size is sufiiciently small to entrap lint.

Another object of our invention is to provide a directly energized line burning screen capable of entrapping lint and operating off household current without an intervening transformer.

Another object of our invention is to provide a directly energized lint burning screen having a widened mesh in the transverse direction to reduce its current requirements and a finer mesh in the longitudinal direction to maintain adequate lint entrapping capabilities.

In another of its broadest aspects, the invention is directed to providing such an elongated strip of lint entrapping and burning screen in a useable package size.

Another object of our invention is to provide a directly energized elongated lint burning screen which requires no transformer, is capable of entrapping lint, and is in useable package size for incorporation into clothes dryers.

Other objects and advantages of the invention will hereinafter become more fully apparent from the following description of the annexed drawings, which illustrate preferred embodiments and wherein:

FIG. 1 is a schematic view of a clothes dryer partially broken away to show a first embodiment of a directly energized lint burning screen package in accordance with one aspect of our invention and its relation to the other parts of a dryer.

FIG. 2 is a section taken along the line 22 of FIG. 1.

FIG. 3 is a section taken along the line 3-3 of FIG. 2.

FIG. 4 is a section taken along the line 44 of FIG. 2.

FIG. 5 is an enlarged schematic view of a directly energized lint burning screen used in the package shown in FIG. 1 and is used to illustrate another aspect of our invention.

FIG. 6 is a frontal view of another embodiment of our invention.

FIG. 7 is a section taken along the line 77 of FIG. 6.

Referring now more particularly to FIG. 1, it shows a dryer indicated generally at 10 having a cabinet 12 in which is rotatably mounted a drum 14. An inlet in the back of the cabinet admits air to the perforate back of the drum through suitable inlet ducting in which is located the dryer heater. From the drum 14, the air exits out the access opening 16 into transition duct 20 through holes in the port plate 18.

The lint burning chamber 22 is located downstream of the transition duct 20 and is connected to a short tubular extension 24 of it. The chamber 22 has a lint burning screen assembly indicated generally at 26 extending across it transverse to the direction of air flow. A pivotally mounted damper 28 is shown in its closed position blocking off the inlet to the chamber 22. The chamber outlet 30 is connected by a flexible conduit 32 to the suction side of a fan 34 which exhausts the air through a suitable conduit 36 to the outside of the cabinet. A second damper 38 is mounted adjacent the outlet 30. It is connected by a common linkage 40 to a drive source 42 so that the dampers move in unison. It is preferable that the damper 28 be movable to a fully closed position; however, the damper 38 may be movable between an open and a partially closed, flow restricting position rather than a fully closed position. The fan 34 is directly driven and drum 14 is belt driven from the dryer motor. The structural details of the belt drive, the motor, the air inlet path with its heater have been omitted for clarity.

In one of its aspects, this invention is directed to a directly energized lint burning screen assembly 26 which is suitable for but not limited to use in the lint burning system just briefly described and more fully disclosed in copending US. patent application Ser. No. 681,392, filed on Nov. 8, 1967 in the names of Thomas J. Brinkman, Thomas H. Fogt, George B. Long and Charles C. Whitler, Jr. and assigned to the assignee of the present invention.

Turning momentarily away from the screen assembly 26, another aspect of the present invention will be discussed in connection with FIG. 5. By way of background, it is desirable to provide a directly energized screen which minimizes the current requirements so as to either eliminate the need for a step-down transformer when operated on a household power source or to require a step-down transformer having a low voltage ratio. Of course, elimination of the transformer altogether provides the least expensive system and also aids in the incorporation of a lint burning system into a conventional dryer. However, even the inclusion of a step-down transformer having a low voltage ratio has advantages over those systems in which the voltage source must be changed by an appreciably high amount. Generally, dryers operate off 220 v. lines and include both 220 v. and v. circuits and in practice, the current carried by these lines is maintained within 15 amps. In order to provide power for other components, it is desirable that the screen draw approximately 11 amps. Accordingly, we have generally directed our effect toward minimizing the current requirements of the lint burning screen and more specifically toward approaching a current requirement of approximately 11 amps. Generally, we have found that a screen of resistance-heated wire will require less current and consequently operate off a higher voltage if a long strip is used with the parallel warp strands individually connected across a voltage source so that each of the strands acts as a parallel current path. Also, we have found that in order to obtain a reasonable width screen and yet maintain a suitable pore size for entrapping lint particles, the woof strands must be of a considerably smaller mesh than that of the warp strands. In other words, the warp strands have been spaced farther apart and the woof strands placed closer together to give a rectangular pore approximating the entrapping characteristics of a square pore having a side dimension somewhere between the length and width dimensions of the rectangular pore. Also, it is advantageous to use a single woof strand woven back and forth through the warp strand. Since the warp strand which is also connected across the voltage source provides an additional current path, the increased length increases its resistance to a point where it is effectively a nonconductor. As is illustrated in FIG. 5, a long strip of screen 44 is connected across two

conductors

46 and 48. The warp comprises parallel strands 50 which act as separate current paths. The Woof 52 is a single strand which is considerably longer than the individual warp strands and is woven back and forth between them, with the adjacent passes of the woof being much closer together than the warp strands. This allows a larger spacing of the warp strands to maximize the strip width with the closer woof passes minimizing the pore openings of the wire to increase its lint entrapping capability. The long length of the single woof strand 52 makes it effectively a nonconductor so that it does not appreciably affect the current flow through the parallel warp strands 50.

In the foregoing description of a directly energized lint burning screen, it was stated that the screen could be constructed so as to be able to be used in an available dryer circuit without a step down transformer. A specific example of such a screen will now be given; however, while it must be borne in mind that other wire sizes, materials, lengths and meshes may be used, the example teaches the approach to the ultimate screen construction which requires test and vertification due to unpredictable factors such as the transfer of heat by radiation from one warp strand to an adjacent one.

To cite a specific example, it has been found that a screen made from 35 mil grade A resistance wire consisting of 80% nickel and chromium requires approximately 0.43 amp to bring it to the required temperature to burn lint. Such a wire offers 53.06 ohms resistance per foot, and when approximately 57 /2 inches long offers a total resistance of 254.25 ohms, which draws approximately 0.43 amp when placed across a 110 v. source. Since the total screen is drawing about 11 amps, this allows 26 parallel wires which would theoretically draw 11.18 amps. We have found that given 26 parallel conductors to be used in a screen, we can construct a screen having a reasonable width and yet adequate lint entrapping capabilities by using 26 parallel warp strands spaced to the inch and interweaving the warp strands with a single woof strand spaced 70 wires per inch (actually 70 passes per inch). This yields a screen strip about 1% inches wide including the selvaged edge due to the single woof strand and 57 /2 inches long. The pore size produced by the different mesh in each direction is sufliciently small to entrap lint. The resistance of the screen is 2.12 ohms per foot for a total resistance of 10.16 ohms which draws approximately 11 amps and is heated sufficiently to burn lint entrapped on it.

, Obviously any change in one of the dimensions of the screen requires changes in the other dimensions. For instance, should a larger diameter wire be used, which would require more current per wire to bring it to a desired temperature, the number of parallel woof strands would have to be decreased, the length of each woof strands may have to be changed and the mesh in each direction probably altered. In some situations it may not be practical to completely decrease the current requirements to a value low enough for direct connection in a dryer circuit; however, in such instances the current is reduced and thus requires less of a step down in voltage, which is likewise advantageous.

Returning to the screen assembly 26 detailed in FIGS. 2, 3, and 4, this aspect of the invention will now be explained. While a directly energized screen comprising a long, narrow strip having a much finer mesh in the longitudinal direction is suitable for entrapping and burning lint and in some instances without a step down transformer, the screen, per se, is impractical for use in domestic dryers unless it can be put into a suitable package size. Assuming a screen as dimensioned above which requires no step down transformer, a package approximately 7 inches square can be constructed as shown in FIGS. 2, 3, and 4. Basically, the idea is to wrap the long strip 44 on a frame 54. The frame 54 comprises a sheet metal top 56, bottom 58, and two sides 60. Each side 60 has two spaced tabs 62 used to secure a side insulator 64 to it. The top portions of the side insulators 64 have suitable cavities to receive the respective ends of a rod 66 which locates a top insulator block 68. The top insulator block 68 has a number of projections 70 on its front and back faces to receive and reverse the screen strip 44. The path of the strip 44 will be discussed below. Mounted adjacent the ends of the insulator block 68 are the

connectors

46 and 48. Since both are the same, only connector 46 will be described. The connector 46 comprises body 71 with an upstanding terminal 72. Depending from the body 71 is a clamping portion 74 which is reversed upon itself to clamp the end of the screen 44 insuring good electrical contact with each of the warp strands 50. It is important that the connector 46 clamp the screen uniformly so that each woof stand makes electrical contact and that the screen is not wrinkled or crimped so as to overlie itself. A second insulator block 76 rests atop the conductor bodies 71. The frame top 56 overlies the insulator 76 and is secured to the sides 60 by tabs which extend through mating slots and are twisted or deformed. Both the insulator 76 and the frame top 56 have holes through which the terminals 72 project. 1

The bottoms of the side insulators 64 have suitable cavities for a bottom rod 78, the ends of which are biased downward by springs 80. A bottom insulator 82 similar to insulator 68 is located by the rod 78. An insulator pad 84 and thermosetting plastic strip 86 are between portions of the screen strip 44 wrapped around the bottom insulator 82, and the frame bottom 58 which is secured to the frame sides 60 by tabs in the same manner as the frame top 56. The screen strip 44 has one end secured to connector 46 by its clamping portion 74. The strip continues downwardly to the bottom insulator 82 and is wrapped around it. In being wrapped around the insulator 82, the strip is indexed a little more than half of its width. The strip 44 continues upwardly to the top insulator where it is again wrapped around and indexed. This wrapping is repeated until the opposite end of the strip arrives at connector 48 and is clamped to it. Once completed, the strip 44 presents four parallel portions or rows adjacent the front of the frame and four parallel rows adjacent the rear of the frame. The back rows overlap the spaces between the front rows and are spaced from the front rows by the width of

insulators

68 and 82 which is about one-half inch. The space between adjacent rows is determined by the width of projections 70. We have found about a quarter inch to be suitable. This spacing together with the tautness of the strip produced by spring loading rod 78 prevents the strip from shorting out on itself. The arrangement of the strip presents the least amount of nonscreened air passage which is a circuitous route between the indexed spaces between the screen rows.

The screen itself and the package described above are for use in those systems in which the lint laden air is caused to flow axially through the screen. In some installations due to space limitations, a radial flow pattern might be preferred; however, some of the same principles can be applied. For instance, as to the package shown in FIGS. 6 and 7 in which the lint chamber 122 is shown as a large square housing having a smaller central outlet conduit 130in this case, the screen package 126 comprises two frame members 132 secured together by four nut and bolt assemblies 134. The frames 132 are spaced apart the width of the screen strip 144 by a number of dowels 136, the ends of which are mounted in the respective frames 132. The assembly includes a first connector 146 to which the strip 144 is connected at one end. The strip continues from the connector 146 in a path which can best be described as a double square spiral with the dowels 136 maintaining the path of the strip 144. The strip ends up and is secured to a second connector 148. The connectors 146 and 148 provide terminals for connection to a suitable power source. In this embodiment, the right-hand frame member 132 is solid so that the lint laden air flows radially through the screen and out the outlet 130.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

We claim:

1. A lint filtering and burning screen comprising in combination:

a pair of spaced electrodes,

a plurality of warp strands extending between said electrodes in a substantially parallel array, said warp strands having electrical resistance values which produce lint-burning temperatures when said electrodes are energized at a household voltage, said warp strands being spaced part into a mesh too large to entrap smaller lint particles normally present in a clothes dryer eflluent or the like,

a single woof strand interwoven with said warp strands in a plurality of passes transverse to said warp strands, said woof strand having an electrical resistance such that its influence on the characteristics of said warp strands when energized is not significant, said woof strand passes being spaced apart into a mesh which is finer than the mesh of the warp strands and which materially improves the lint-entrapping characteristics of the screen over a screen having a mesh in both directions equal to the mesh of said warp strands.

2. The lint filtering and burning screen as defined in claim 1 wherein said warp and woof strands are of the same material, wherein the mesh of said warp strands is approximately 25 strands/inch and wherein the mesh of said woof strand is approximately 70 passes/inch.

3. The lint filtering and burning screen as defined in claim 1 wherein the length, diameter, number and material of said strands is such that said screen draws approximately 11 amps when connected to a 110 volt power source.

4. The lint filtering and burning screen as defined in claim 1 wherein said warp and woof strands are of a nickel-cnromium alloy, wherein the mesh of said warp strands is approximately 25 strands/inch, wherein the mesh of said woof strand is approximately 70 passes/ inch, and wherein the length and diameter of said warp strands is such that said screen draws approximately 11 amps when connected to a 110 volt power source.

5. A lint filtering and burning screen assembly comprising in combination:

a frame having a pair of spaced electrodes,

an elongated resistance heatable wire screen strip connected to said spaced electrodes adjacent its opposite ends, respectievly, said strip having a plurality of warp strands in the longitudinal direction, said warp strands being spaced apart into a mesh too large to 6 entrap smaller lint particles normally present in a clothes dryer efiluent or the like,

a single woof strand interwoven with said warp strands in a plurality of passes transverse to said warp strands, said woof strand passes being spaced apart into a mesh which is finer than the mesh of the warp strands to improve the lint entrapping characteristics of the screen over a screen having a mesh in both direction equal to the mesh of said warp strands, said wire screen strip having sufiicient length so that each of said warp strands is brought to the combustion temperature of lint when connected to a household power source without the additive current carried by said warp strands being excessive, and

means to mount said strip on said frame in such a manner that the screen does not touch itself.

6. The lint filtering and burning screen assembly as defined in claim 5 wherein said warp and woof strands are of the same material, wherein the mesh of said warp strands is approximately 25 strands/inch and wherein the mesh of said woof strand is approximately 70 passes/ inch.

7. The lint filtering and burning screen assembly as defined in claim 5 wherein the length, diameter, number and material of said strands is such that said screen strip draws approximately '11 amps when connected to a volt power source.

8. The lint filtering and burning screen assembly as defined in claim 5 wherein said warp and woof strands are of a nickel-chromium alloy, wherein the mesh of said warp strands is approximately 25 strands/inch, wherein the mesh of said woof strand is approximately 25 strands/inch, wherein the mesh of said woof strand is approximately 70 passes/inch, and wherein the length and diameter of said warp strands is such that said screen strip draws approximately 11 amps when con nected to a 110 volt power source.

9. A lint filtering and burning screen assembly comprising in combination:

a rectangular frame,

a first insulator mounted in said frame,

an electrical connector adjacent each end of said first insulator,

an elongated strip of resistance-heatable screen secured adjacent its opposite ends to said connectors, respectively, said screen comprising a plurality of warp strands in substantially a parallel array in the longitudinal direction and a single woof strand traversing said warp strands in a plurality of passes having a finer mesh than said warp strand,

a second insulator in said frame substantially parallel to sadi first insulator, said strip being wrapped around said spaced insulators into two spaced layers, each layer comprising a plurality of parallel rows spaced from each other less than the width of said strip,

indexing means on said insulators orienting each row parallel to each other row and indexing the rows in one layer with respect to the rows in the other layer with the rows in each layer overlying the spaces between the rows in the other layers, and

means to maintain said strip taut.

10. The unit filtering and burning screen assembly as defined in claim 9 wherein said warp and woof strands are of the same material, wherein the mesh of said warp strands is approximately 25 strands/inch and wherein the mesh of said woof strand is approximately 70 passes/ inch.

11. The lint filtering and burning screen screen as de fined in claim 9 wherein the length, diameter, number 7 and material of said strands is such that said screen draws approximately 11 amps when connected to a 10 volt power source.

12. The lint filtering and burning screen as defined in claim 9 wherein said warp and woof strands are of a nickel-chromium alloy, wherein the mesh of said warp strands is approximately 25 strands/inch, wherein the mesh of said woof strand is approximately 70 passes/ inch, and wherein the length and diameter of said warp strands is such that said screen draws approximately 11 amps when connected to a 110 volt power source.

13. A lint filtering and burning screen assembly comprising, in combination:

an electrically insulated frame having spaced end plates with a pair of spaced electrodes and a plurality of dowels arranged in a double spiral extending therebetween,

an elongated resistance-heatable wire screen strip connected to said electrodes adjacent its opposite ends, respectively, said screen strip having a plurality of warp strands in the longitudinal direction, said warp strands being spaced apart into a mesh too large to entray smaller lint particles normally present in a clothes dryer eifluent or the like.

a single woof strand interwoven with said warp strands in a plurality of passes transverse to said warp strands, said woof strand passes being spaced apart into a mesh which is finer than the mesh of said warp strands to improve the lint entrapping characteristics of the screen over a screen having a mesh in both directions equal to the mesh of said warp strands,

said wire screen strip being mounted on said frame and guide by said dowels into a double spiral configuration so that the wire screen strip does not touch itself and has a sufficient length so that each of said warp strands is brought to the combustion temperature of lint when connected to a 110 volt power source, and

said warp and woof strands having a length, diameter number and material such that said screen strip draws approximately 11 amps when connected to said source.

References Cited UNITED STATES PATENTS 1,733,116 10/1929 Coups 2458 X 2,063,663 12/ 1936' Downward.

2,412,843 12/ 1946 Sparagen 219-545 2,496,279 2/ 1950 Ely et a1 338-20 8 X 2,522,542 9/ 1950 Schaeffer 338-208 X 2,912,661 11/1959 Balestrini 338-316 X 2,984,357 5/1961 Kuiferath 209-238 X 3,061,942 11/1962 Schofield 34-82 3,268,080 8/1966 Eberly -428 X 3,344,257 9/1967 Moeller 338-208 X 3,408,794 11/ 1968 Stoddard 55-282 OTHER REFERENCES 8,398 4/ 1897 Great Britain.

ANTHONY BA'RTIS, Primary Examiner US. Cl. X.R.

2 2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,541, 303 Dated November 17, 1970 Inventor(s) Thomas J. Brinkman, Thomas H. Fogt, and Charles C.

Whistler, Jr. It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

a o Column 1, line 47, "line" should read --lint--; Column 2, line 44, "Whitler" should read --Whistler;

line 66, "effect" should read effort-: Column 3, line 44, "amp" should read --amps--;

line 48, "amp" should read -amps-; line 70, "strands" should read --strand-.

In the Claims: Claim 4, line63, "nickel-enromium" should read --nickel chromium--; Claim 5, line 9, "direction should read -directions--: Claim 8, lines33, 34 and 35, delete "appriximately 25 strax inch, wherein the mesh of said woof strand is"; Claim 9, line 53, "sadi" should read -said-:

line 61, "layers" should read -layer--; Claim 11, line 69, delete "screen", second occurrence; line 72, "10" should read --llO--; Claim 13, line 18, "entray" should read -entrap--;

line 29, "guide" should read --guided--.

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