US2142042A - Process for drying - Google Patents

Description

DB0 27, 1938. G, E. BOWDOIN ET AL v2,142,042

PROCESS FOR DRYING Filed Oct. 12, 41935 17 Sheets-Sheet 2 TE]. a.

-|NVENTORS 9601' e E. Bowdoin W6 [6 152 Sfrorgld e v @MMF mmmzx Dec. 27, 1938. a. E. BOWDOIN ET AL 2,142,042

PROCESS FOR DRYING Filed Oct. 12, 1935 l7 Sheets-Sheet 3 INVENTORS gear a E. Bowdozlm M'l am Strorid e QRNE Dec. 27, 1938.

PROCESS FOR DRYING Filed-Oct. 12, 1935 G. E. BOWDOIN ET AL 1'7 Sheets-Sheet 4 INVENTO S BY @AA M M QBNEX 17 Sheets-Sheet 5 PROCESS FOR DRIYING Filed 0ct 12, 1935 G. E, BOWDOIN ET AL 2% w, o w .1 w E T040 N. N 0 m WES m 7,, 1938. a, E. BOWDOIN EAL v 2,142,642.

PROCES S FOR DRYING Filed Oct. 12, 1935 17 sheets-sheet 6 QBNEY G. E. BOWDOIN ET AL 0 PROCESS FOR DRYING Filed Oct. 12, 1955 17 Sheets-Sheet '7 INVENTORS 2: 90;- e E.f owci ozln 61 am Strobmaye Dec. 27, 1938. BOWDOlN ET AL 2,142,042

PROCESS FOR DRYlNG FiledfOct. l2, 1955 17 Sheets-Sheet 8 )NVENTORS QBNEX 27, 1938. G. asownom ET AL 2,142,042

PROCESS FOR DRYING Filed Oct. 12, 1935 l'7 Sheets-Sheet l0 INVENTORS GeorqeflBawdoin VVZZZLcgn Strain-1x196 TQBNEY Dec. 27, 1938 s. E. BOWDOIN Er AL PROCESS FOR DRYING Filed Oct. 12, 1935 17 Sheets-Sheet ll r e 2 am w was 2 m" m w 4m w/R v o .0 m N MW U .2 \(NJ I A KOFOZ WLMI PI Dec. 27, G E BO ET AL 2,142,042

PROGES 5 FOR DRYlNG Filed Oct. 12, 1935 1'? Sheets-Sheet l3 Q @Q? @@M a "gum.

gnlllllnm INVENTORS I Gear eEBowdoin William Strobrzldye BY @M/ {QM QENEY Dec. 27, 1938.

G. E. aowoom ET AL,

PROCESS FOR DRYING Filed Oct. 12, 1955 17 Sheets-Sheet l5 INVENTORS C} 'qe EBowcZoirz William Strobri e BY y v f E Dec. 27, 1938. BQWDQIN ET AL 2,142,042

PROCESS FOR DRYING Filed Oct. '12, 1935 17 Sheets-Sheet l6 INVENTORS Georye ELBowdoin mlg am stl 'obridye @M M M QBNEY Dec. 27, 1938. G, g BOWDOIN T AL 2,142,042

PROCESS FOR DRYING Filed Oct; 12, 1935 17 SheetsSheet 17 INVENTORS eorcefliB ou/doin William sii'obridye BY $3M ATTORNEYS Patented Dec. 27, 1938 UNITED STATES PATENT OFFICE PROCESS FOR DRYING Application October 12, 1935, Serial No. 44,724

4 Claims.

This invention relates to a method useful in dry cleaning, and more particularly to drying materials which have previously been treated with an inflammable cleaning solvent.

Dry cleaning processes may be broadly classifled in two categories, viz.: those employing (l) inflammable solvents, such as benzene, gasoline, cleaners naphtha, Stoddard solvent, and the hydrogenation products of naphthalene-tetralin and decalin; (2) the chlorinated hydrocarbon products, such as carbon tetrachloride and tetrachlorethylene. The high cost and extremely volatile nature of the latter group of solvents render them unsuitable for dry cleaning in large installations, except in closed systems. These and other disadvantages would be deterrent of their use for dry cleaning purposes, were it not for safety considerations due to their non-inflammable nature. On the other hand, the fact that the petroleum distillates and hydrogenation products of the first group are all explosive at some degree of air-vapor concentration and temperature has heretofore greatly offset the many advantages Which are otherwise assured by their use.

For many years Stoddard solvent, a mixture of petroleum distillates, having a flash point in the neighborhood of 105 F., has had a wide use in dry cleaning processes, but since its flash point is within the range of possible workroom temperatures, its use, and similarly, the use of solvents of lower flash point, has been penalized in the sense that various statutes, ordinances, and rulings of fire insurance rate-setting boards have required dry cleaning operations involving the use of such inflammable solvents to be carried on in separate or detached buildings of special construction.

Dry cleaning according to the open batch system usually includes handling a batch of clothing or other articles in successive stages, as follows: the batch is first treated in a washing machine, preferably of the horizontal cylinder type, by agitation in intimate contact with the solvent for o a period of sufficient duration to accomplish the desired degree of cleansing. It is then rinsed in clean solvent, drained, and transferred to a centrifugal extractor where from to of the remaining solvent is thrown off. The clothing is then transferred to apparatus where it is dried and deodorized in a rotary drum through which heated air is drawn. The air is ordinarily heated by a set of steam coils over which the air passes on its way to the drum.

It will be understood that danger of explosion in the washer is extremely remote, since in such apparatus the air is not heated and attains such a high degree of solvent saturation that ignition is practically impossible under any likely conditions of operation. It is to be noted, however, 5 that precautions are usually taken to prevent static electrical discharges. The operation of the centrifugal extractor is also substantially free from explosion risk.

The chief point of danger lies in the drying apparatus, for here, according to usual practice, highly heated air is brought into contact with the solvent under conditions likely to foster the accumulation of an explosive mixture. In the past, it has been known to attempt to remedy this danger by drawing the heated air rapidly through the dryer in the hope of keeping the air-vapor mixture below explosive concentration. But such methods as have been developed on this principle, although perhaps in some cases operative to re- 29 duce the danger somewhat, are in many respects defective and cannot be depended upon to lower the risk to the degree that safety demands. For example, soon after the beginning of the drying operation, while the clothing still contains an 25 appreciable quantity of solvent, the highly heated air might take up sufiicient vapor to produce, it only for a brief period, an explosive mixture at or above the flash point of the solvent.

To a lesser degree, the danger inherent in the use of solvents having flash points commensurate with room temperatures is also present in the use of the hydrogenation solvents above mentioned. Hydronaphthalenes are now produced commercially by certain German processes, and otherwise, 35 which not only offer superior solvent qualities, but which range in flash point from about F. to F. with boiling points covering the range from about 365 F. to around 420 F. It is also possible today to purchase at a reasonable cost hydrocarbon distillation products of excellent solvent quality, having a flash point close to 140 F. and a distillation range from 350 F. to 410 F. The advantages due to the superior solvent quali- 5 ties and relatively high flash point of such solvents are somewhat offset by their higher boiling points (relative to the low flash point solvents hereinbefore discussed) necessitating as they do higher temperatures for accomplishing the complete drying and deodorization of the dry cleaned goods within an economically short period 01' time.

, Having in mind the great demand existing for accomplishing with safety dry cleaning and dry- 55 ing operations with the employment of solvents having the characteristics of any or all of the inflammable solvents hereinbefore mentioned, it is an object of the present invention to provide a process or processes for attaining this purpose. It is a further object of this invention to provide a process of the character described according to which the materials to be dried are first subjected to a flow of air maintained at a safe temperature relatively to the flash point of the solvent used in the preceding washing operation to remove the greater part of said solvent, then subjected to a flow of air at a temperature or temperatures considerably higher than the said flash point, and, finally, subjected again to a flow of air at a safe temperature relatively to the flash point to cool and complete the deodorization of the said materials and bring the temperature within the dryer down to a point where the cycle of operation may immediately be repeated with safety.

More specifically, it is an aim of the present invention to maintain at all times safe temperatures in relation to the flash point of the solvent contained in the materials treated and in relation to the vapor concentration during the various stages of the drying cycle.

Further objects of the invention are in part obvious and in part will be pointed out hereinafter.

The invention accordingly consists in the several steps and relation and order of each of the same to one or more of the others, as will be hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are shown two illustrative embodiments of apparatus capable of use in carrying out the purposes above mentioned:

Fig. 1 is a front elevation of a drying tumbler embodying features of the present invention;

Fig. 2 is a right side elevation thereof;

Fig. 3 is a left side elevation thereof;

Fig. 4 is a back elevation of the tumbler;

Fig. 5 is a cross-section taken on line 5-5 of Fig. 4;

Fig. 6 is an enlarged sectional detail of the cylinder construction on line 66 of Fig. 5;

Fig. 7 is a top plan view of the rear portion of the tumbler showing the location of certain of the operating and control devices;

Fig. 8 shows on a larger scale the upper portion of the tumbler, and the control mechanism in the same position it occupies in Fig. 3, the shell door being in open position;

Fig. 9 is a view similar to Fig. 8 showing the control mechanism in a different position and the shell door closed;

Fig. 10 is a view of certain elements of the control mechanism in positions different from those occupied by the same elements in Figs. 3, 8, and 9;

Fig. 10A is a view showing the control elements of Fig. 10 in still diiferent positions;

Figs. 11 and 12 are respectively back and side elevations, on an enlarged scale, of the belt pulley and belt shifting header assembly;

Figs. 13 and 14 are respectively elevations of mechanically and electrically actuated switch mechanisms which become effective at different stages of the drying cycle to control certain phases of that cycle;

Fig. 15 is a wiring diagram pertaining to the apparatus and devices shown in the preceding figures;

Fig. 16 is a somewhat diagrammatic view of a half-turn motor and circuit-maintaining switch therefor;

Fig. 17 is a somewhat diagrammatic view of a timing device;

Fig. 18 is a left side elevation, similar to Fig. 3, of a modified form of drying tumbler, adapted for use with low flash point solvents, the upper rear portion of the casing being broken away to show specific features;

Fig. 19 is a rear elevation of the modified drying tumbler;

Fig. 20 is a right side elevation of the coil box shown in section in Fig. 18;

Fig. 21 is a wiring diagram pertaining to the apparatus and devices shown in Figs. 18 to 20;

Fig. 22 is a piping diagram of the pneumatic control system employed in the modified drying tumbler; and

Fig. 23 is a view taken from the front of the tumbler showing an instrument board supporting a master control valve and other control devices, and an air compressor for supplying the master control valve with compressed air.

Similar reference characters refer to similar parts throughout the various views of the drawings.

It will be seen from the foregoing that in carrying out the general purposes of this invention, the apparatus and controls therefor may be modified to suit the special conditions under which dry cleaning takes place. Having in mind the facts: that the treatment of the clothes in the drying tumbler is first conducted at a temperature predetermined in relation to the flash point of the particular solvent used in the preceding steps of the dry cleaning process, and that the length of this preliminary drying stage is determined by test as suflicient to dry the clothing to a degree making it possible and safe thereafter to submit the clothing in the drying tumbler to higher heat, in order rapidly to complete the drying of the clothes and effect eflicient deodorization thereof, it will be evident that in the case of a solvent having a flash point substantially above any possible workroom temperature the heat during the preliminary heating period may with safety be maintained at a temperature well above that of the workroom but substantially below the flash point of the particular solvent used. Under such conditions, there can be no danger of explosion taking place within the tumbler. Drying apparatus for a solvent of this nature will include heating means and heat and time controls, adapted to heat the air entering the tumbler to the desired low heat drying temperature and maintain that temperature long enough to accomplish the desired degree of drying.

Under other conditions, as when the solvent used for dry cleaning has a flash point below or substantially at workroom temperatures, the principles of the process remain the same, but the apparatus and controls will be of a character to render possible holding the temperature of the air in the drying tumbler during the low heat drying period not only below the flash point of the solvent, but also, if necessary, below the temperature of the workroom.

To meet the conditions of the first case, apparatus made in accordance with Figs. 1 to 15 of the drawings may be employed, although it is obvious that other forms of apparatus may be designed to carry out the principles of the invention. This form of apparatus will now be described and subsequently the modification disclosed in Figs. 18 to 23 of the drawings, especially adapted for the drying of clothes which have been treated with a relatively low flash point solvent, will receive attention.

Description of apparatus according to Figs. 1-15 Reference to Figs. 1 to 5, inclusive, may be had for a general conception of the preferred form of apparatus. There is disclosed a tumbler comprising an outer shell or casing I0 having rotatably mounted therein a foraminous drum The drum H is surrounded by an internal cylindrical shell l2 which encloses the drum for approximately three-quarters of the periphery thereof, the hinged outer shell door i3 at the front of the tumbler housing completing the enclosure. To the rear of the drum chamber is formed a rectangular coil box l4, connected with the atmosphere through the rear plate of the housing by means of two air inlets l5 and I6, the inlet |5 giving access of air to the upper portion of the coil box and the inlet l6 at a point near the bottom of the coil box. These two inlets are equipped respectively with rectangular air intake nozzles I! and I8 adapted to be opened or closed to the atmosphere by means of dampers l9 and 20. The damper I9 is rotatably mounted upon a shaft 2| and similarly the damper 20 is rotatably mounted upon a shaft 22. These dampers are connected in predetermined relationship by means of an adjustable rod 23, the length of the rod and its mode of attachment to the two dampers being such that whenever one of said dampers is open the other will be closed. The operation of the dampers is automatic and is controlled by means of a half-turn motor P, the crank pin P of which is connected by means of an adjustable connecting rod 24 to the crank arm 25 mounted upon the shaft 2| of the upper damper.

' The heater The coil box if is divided into two compartments M and M by means-of a vertical partition 26 which extends downwardly from the top plate of the coil box to within a short distance of the bottom of the coil box. Thus the two coil box compartments communicate at their lower ends adjacent the lower air inlet l6. Located in the compartment M is a steam coil 21 and in the compartment i4 is a steam coil 28. Air from the inner compartment M is led to the top of the tumbler and admitted to the tumbler drum through an opening 29 in the inner shell it. The outlet from the cylindrical drum chamber is through an opening 30 at the bottom of the shell l2, opposite the opening 29. This outlet 36 forms a passage for the air into the lower part of the tumbler housing beneath the drum chamber, where there is located a rotary fan 3| to which air is admitted from the, lower part of the housing through an inlet 32 formed in the fan housing 33. The outlet of the fan housing 33 is at 34 projectingthrough the rear wall of the tunabler housing near the bottom thereof.

The fan 3| is driven by a direct connected motor 35 and serves to draw air through the air inlet I5 over both coils 28 and 21, or through air In order that heat shall not be transferred from the coil box to the tumbler drum otherwise than by the heated air drawn through the drum, the coil box should be well insulated from the drying space within the tumbler. It is therefore desirable to insulate the coil box, as by means of an adequate heat-insulating medium, as indicated at |5| in Fig. 5,

The steam connections to and from the independently connected coils 21 and 28 may best be understood by reference to Figs. 1, 2, 4, and 7. Live steam is brought to a fitting 36 which connects with a cross fitting 31 having connections to the upper ends of both the inner and outer steam coils 21 and 28. Connection from the fitting 36 to the cross fitting 31 is made through a main steam line 39 and a branch steam line 40. In the main steam line 39 is disposed a shut-off valve 4| operated automatically by means of a lever 42 suitably connected to a crank arm 43 fastened upon the damper-operating shaft 2|. Thus the steam through the main line to both coils is controlled by operation of the half-tum motor P. In by-pass or branch line there is installed a thermostatically controlled valve 44,

the diaphragm chamber 44 of which is connected by means of flexible tubing 44 to the bulb 45 located in the air space at the top of the tumbler between the outer and the circular inner shell. Thus the operation of the valve 44 is controlled by the temperature of the air at the top of the tumbler before it has access to the tumbler drum containing the materials being dried. Steam coils 21 and 28 are connected at their lower ends by means of pipes 21 and 28 to the steam return pipe I53. The tubular drum H is journaled in bearings 46 mounted on brackets 41 secured to the side plates of the tumbler housing.

Cylinder drive Upon the drum shaft H is mounted a spur gear 48 driven by a pinion 49 mounted upon a jack shaft 55 forming part of a pulley and belt shifting header assembly, for a better under standing of which reference is made to Figs. 11 and 12 in which the jack shaft 50 is shown to be rotatably mounted in a pair of bearings 5|, 52 carried by a header bracket or arm 53. This bracket is bolted to the side of the tumbler housing. The jack shaft 50 carries a tight pulley 54 and a pair of loose pulleys 55, 56. Also loosely mounted upon the shaft 50 is the header worm 51 which has a pin-andslot connection with the hub of the loose pulley 56 so as to be driven thereby. Mounted upon the header bracket 53 in co axial relation to the shaft 50 is a header arm assembly comprising the support 58, to which is pivotally connected the belt shifter fork 59.

The header arm assembly includes a worm gear 60 on support 58 meshing with the worm 51, and a reciprocating slide shaft 6i, slidably and rotatably mounted at the upper end of the support 58 in a block 62. Projecting from the block 62 parallel to the shaft Si is a guide rod 63. A weighted pin or header fall 64 secured to and extending at right angles to the slide shaft 6| shifts with the slide shaft about its axis so that the pin 64 may engage the notch 65 formed in the upper end of the shifter fork 59 when the pin 64 is swung in one direction to a horizontal position, and when swung in the opposite direction to a horizontal position will be free of the shifter fork 59, but will engage one or the other of the beveled surfaces 66 formed on the block 62 and ride down to a neutral po-

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