US3279151A

US3279151A - Compressed air dehydration system with desiccant reactivating means

Info

Publication number: US3279151A
Authority: US
Inventors: Jr George C Kauer; Louis E Brooks
Original assignee: Air Technologies Inc
Current assignee: Air Techniques Inc; Air Technologies Inc
Priority date: 1964-03-23
Filing date: 1964-03-23
Publication date: 1966-10-18
Anticipated expiration: 1983-10-18

Description

Oct- 18, 1966 G. c. KAUER, JR., ETAL 3,279,151

COMPRESSED AIR DEHYDRATION SYSTEM WITH DESICGANT REACTIVATING MEANS 2 Sheets-Sheet 1 Filed March 25, 1964 COMPRESSOR INVENTORS LOU/S E. BROOKS BY GEORGE C. KAUER, JP.

A 7' TOR/VEV Oct- 18, 1966 G. c. KAUER, JR.. ETAL 3,279,151

COMPRESSED AIR DEHYDRATION SYSTEM WITH DESICCANT REACTIVATING MEANS Filed March 25, 1964 2 Sheets-Sheet 2 Oumar 75 ll V18 Arrow/ey United States Patent O CMPRESSED AIR DEHYDRATIGN SYSTEM WITH DESICCANT REACTIVATING MEANS George C. Kauer, Jr., Westbury, and Louis E. Brooks, Great Neck, N.Y., assignors to Air Techniques, Inc.,

New Hyde Park, N.Y., a corporation of New York Filed Mar. 23, 1964, Ser. No. 353,850 Claims. (Cl. 55-26) This applic-ation is a continuation-in-part of our application Serial No. 250,422, filed January 9, 1963.

This invention relates generally to apparatus for drying compressed gases, and more particularly to a cornpressed air dehydration system in which means are provided for reactivating, upon command, the systems desiccant, or drying agent.

It is one object of the present invention to provide improved means to reactivate, that is to say, remove absorbed water vapor, from the desiccant in a compressed air dehydration system.

It is another object of the invention to enable compressed air to be used by supplying it from the compressed air source lduring reactivation of the desiccant, if such use is needed.

Another object of the invention is to provide for the supply of the compressed air during the reactivation cycle of the desiccant to the compressed `air operated instrument without appreciable reduction of the `air pressure.

Another object is to provide for automatically initiating the reactivating cycle when the air compressor is initially put into operation under manual control.

A further object of the invention is to reactivate the desiccant automatically each time the compressor is started.

These and other objects of the invention are accomplished, broadly, by the provision of a chamberfor containing a desiccant, means for passing a compressed gas to be dried through the desiccant chamber and from there to a compressed gas utilization device, and means for expelling the moisture absorbed by the desiccant from the chamber.

One feature of the invention resides in an arrangement for drawing compressed gas from the system and if needed, during the interval in which the moisture is being expelled from the desiccant chamber.

Another feature of the invention involves an automatic control unit which transforms the absorbed moisture in the desiccant to vapor and exhaust the vapor into the atmosphere each time the systems compressor is turned Still another feature of the invention pertains to an arrangement for passing the moist compressed gas through the desiccant chamber in one direction for the purpose of drying the gas, and for passing a thin stream of the gas through the chamber in the opposite direction for the purpose of expelling the moisture absorbed by the desiccant into the atmosphere.

The foregoing and various other objects, features and advantages of the invention will be more thoroughly understood by reference to the following detailed description of a preferred embodiment of the invention in conjunction with the accompanying drawing of which:

FIG. 1 is a schematic View, partially in section of a compressed gas drying system constructed in accordance with the invention;

FIG. 2 is one embodiment of an electrical control system for operating the drying system;

FIG. 3 is another embodiment of an electrical control system for operating the drying system;

FIG. 4 is a view similar to FIG. l, showing another preferred embodiment of the invention; and

3,279,151 Patented Oct. 18, 1966 ice FIG. 5 is a View similar to FIG. 3, showing another preferred electrical -control system for the compressed air supply apparatus.

With reference to FIG. 1 of the drawing, a compressed air drying system is shown in which compressed air from the tank of a conventional compressor (not shown) is passed through an inlet T joint 1, a connecting pipe 2, and ports a and b of two-way solenoid operated valve 3 to a flow-through desiccant chamber 4 for removing moisture from the gas, and from there as suciently dry compressed air through a T joint 54, an elbow joint 5, a check valve `6 and an outlet T joint 7 to a compressed air utilization device, for example, a dental drill (not shown). As shown, desiccant chamber 4 basically comprises an externally threaded hollow cylinder having shallow internal shoulders 8 at either end thereof lfor supporting screens 9. Internally threaded caps 10` enclose the chamber 4 at either end and secure screens 9 in place against their respectiveshoulders 8. A desiccant, shown generally as 11, which by way of illustration and not restriction may be silica gel or activate-d alumina, is contained in chamber 4 between screens 9. Associated with chamber 4 is a heating band 12 which is electrically connected to the control circuitry of the system by conductors 13.

Solenoid operated valve 3 comprises three ports; namely, port a which admits air from the compressor tank, port b which is connected to one cap 10 of the desiccant chamber, and port c through which water vapor from the desiccant chamber is exhausted to the atmosphere as will be explained in greater ydetail hereinafter. As shown, solenoid operated valve 3 is essentially in the shape of a T and includes a pair of walls 13 and 14 for internally separating from each other the arm of the T terminating in port c from the arms of the T terminating in ports ,a and b. A passage 15 permanently interconnects the latter two -arms of the valve. Longitudinally disposed in the arm of the valve terminating in port a is a cylindrical core 16 which tapers sharply in conical fashion to valve stops 17 and 18 at opposite ends of the core. A disc 19, parallel to wall 14 and having an aperture 20 therein tapered to receive the valve stop 18, is disposed adjacent to port a. Wall 14 includes an aperture 21 situated opposite aperture 20 and tapered to receive valve stop 17. Posts 22, which project from the walls of the valve, form a guideway in which valve core 15 is shifted between apertures 20 and 21 under the control of solenoid 23 which is electrically coupled to the control circuitry by conductors 24.

Solenoid operated valve 3 is oriented so that when solenoid 243 is deenergized, the combined forces of a non-illustrated biasing spring, and of the air pressure from the compressor tank, force valve stop 17 into aperture 21, as shown in the drawing, thereby allowing air from the compressor tank to ow from port a to port b through passage 15, and thence into the desiccant chamber for drying. When solenoid 23 is energized, as will be explained hereinafter, core 16 is longitudinally shifted such that aperture 20 is closed by valve stop .18 and water vapor from the desiccant chamber is allowed to exhaust to the atmosphere through port b, passage 15, aperture 21 and port c.

Connected to the

stems

25 and 26 of T joints 1 and 7 is a pressure responsive by-pass valve 27 comprising an inlet duct 2-8, an outlet duct 29 and a valve opening 30 separating these ducts. Seated in valve opening 30 is a valve 3 1 supported from below by a compression spring 32 and from above by a rod 33 which bears against a diaphragm 34. As sho-wn, the under surface of diaphragm 34 is open to outlet duct 29. Valve `27 also includes a pressure chamber 35 situated above diaphragm 34 which is lled with air from the compressor tank lvia a tap 3 36. It will be apparent to those familiar with pressure responsive valves such as 27 that when the pressure above diaphragm 34 is substantially equal to the pressure be- I low the diaphragm, that is to say, when the pressures at the inlet and outlet ducts are substantially equal, the force of the diaphragm on rod 33 tending to open valve 31 is nullified and spring 32 urges valve 31 to closed position. However, when the pressure at outlet duct v29 falls `below the pressure at inlet duct 28, the greater pressure above diaphragm 34 forces rod 33 to unseat valve 31, and thereby opens the valve through aperture 30, there being sufficient clearance under said diaphragm so that it can flex to open the valve. It should be evident to one skilled in the art that numerous other type Valves could be substituted for pressure sensitive valve 27 without departing from the principles of the invention. For example, a solenoid operated valve such as valve 3, only modified such that port a is permanently closed, would be equally suitable.

With solenoid 23 deenergized the valve would be closed, and with the solenoid operated the valve would be open, thereby allowing the passage of air between ports b and c.

Connected in line 37, which joins outlet duct 29 of valve 27 to stem 26 of T joint 7, is a T joint 38. The stems of

T joints

54 and 38 are connected by a two layer filter 39 and dics 40 which provides a small orifice for filtered air In a prises a loosely packed first layer 41 and a more tightly packed second layer 42 both of pressed copper wool.

Disc 40 is secured in the line yby being interposed, along with a suitable sealing material, between -two flanged pipe members. The pipe members are fastened together by an internally threaded coupler 43 which bears against the face of one flange and is threaded upon the rim of the other flange so that turning of the coupler draws the flanges together. A suitably sized orifice is provided in disc 40 by puncturing the disc and inserting .therein a thin Y wire filament `45.

The compressed air drying system of FIG. l operates in two distinct cycles, a drying cycle and a desiccant reactivation cycle. During the drying cycle solenoid 23 of valve 3 is deenergized, thereby allowing core 16 to assume the position shown with aperture 20 open and aperture 21 closed. Consequently, moist air from the cornpressor tank passes through T joint 1, connecting line 2,

port a, aperture 20, passage 15, port b, desiccant chamber '4 where moisture is removed, T joint 54, elbow 5, check valve 6 and T joint 7 to the compressed air utilizer.

Since only a slight drop in pressure is encountered around :the loop just described, the pressures at the inlet and 4 outlet ducts, 28 and 29, respectively, of bypass valve 27 are substantially equal, and consequently valve 27 is closed by the force of spring 32. Hence, during the drying cycle all air from the compressor tank is dried in the desiccant chamber before utilization.

During the reactivation cycle, both solenoid 23 and heating band 12 are energized, as will be explained hereinafter. Energization of solenoid 23 shifts core 16 along l the guideway provided by posts 22 such that apertures 20 and 2i1 are closed and opened, respectively. Consequently, desiccant chamber `4 is open to the atmosphere through port b, passage 15, aperture 21 and port c, and the pressure at T joint 7 begins to drop accordingly. As the pressure at T joint 7 drops, a pressure differential is created across diaphragm 34, and valve 27 opens. During the reactivating cycle, the compressed air utilizer is normally not operated but if it is essential to operate the utilizer, compressed air can be drawn for that purpose from the compressor through valve 27 and conduit 37 as later explained.

Energization of heating band 12 raises the temperature of desiccant 11 and transforms the absorbed moisture into water vapor. This vapor is then driven from chamber 4 and exhausted to the atmosphere through ports b and c of the solenoid operated valve by means of the small stream of filtered air which bleeds through the orifice in disc 43. Approximately midway in the reactivation cycle heating band 12 is deenergized so that desiccant 11 is restored to a suitable temperature for moisture absorption when the drying cycle commences. When the reactivation cycle terminates, solenoid 23 is deenergized, allowing valve stop 17 of core 16 to once again block aperture 21 and concomitantly opening ports b and c to each other.

One embodiment of a control unit capable of supplying appropriately timed operating potentials to solenoid 23 and heating band 12 is shown in FIG. 2. The control unit comprises line 45 which is connectable through armature 46 of a first switch to heating band 12 which is in series with a normally closed thermal sensitive bimetallic switch 47, and through armature 48 of a second switch to the winding of solenoid 23 which is in series with a rectifier 49. A pilot lamp 50 is disposed in parallel with the rectifier-solenoid combination so as to indicate when the system is operating in the reactivation cycle. The current supply for line 45 may comprise the usual wall outlet providing volt 60 cycle/sec. power. As shown, the actuation of armatures 46 and 48 is controlled jointly by a conventional spring wound timer mechanism 51. In the embodiment of the invention described herein, mechanism 51 is a thirty minute timer which closes the armatures 46 and 48 at the start of a timing cycle, opens armature 46 at the end of fifteen minutes, or midway during a `complete timer cycle, and opens armature 48 upon completion of the cycle. Numerous devices answering the foregoing description of timer mechanism 51 are available commercially, and consequently further explanation of such apparatus is believed unnecessary. v

Normally the system operates in the drying cycle, that is to say, with armatures 46 and 48 separated from their associated contacts, and therefore with heating band 12 and solenoid 23 deenergized. When it is desired to reactivate the desiccant, timer 51 is wound to the thirty minute mark, whereupon armatures 46 and 48 close with their associated contacts. Accordingly, heating band 12 is energized through normally closed thermostat switch 47 and transforms the absorbed moisture in the desiccant to vapor. Concurrently, solenoid 23 is energized through rectifier 49, thereby opening bypass valve 27 (FIG. 1) and providing a stream of filtered air through the orifice in disc 40 with which the vapor in the desiccant chamber 4 is driven by a thin stream of compressed air t-o the atmosphere through port c of valve 3. Thermostat switch 47 is so situated to regula-te the temperature of heating band 12 by interrupting the flow of current in conductors 13 when the temperature of the band rises above a predetermined level. Switch 47 opens and interrupts the heating operation, permitting the desiccant to cool gradually to a temperature suitable for drying. At the end of fifteen minutes contact 46 opens and at the end of thirty minutes contact 48 opens, thereby deenergizing solenoid 23 and shifting the system back to the drying cycle. It will be observed that during the reactivation cycle, compressed air, although moist, is available to the compressed air utilizer via bypass valve 27,

i but normally the dentist or other operator would not use the utilizer and hence no considera-ble flow of compressed air from the source would occur.

FIG. 3 illustrates a fully automatic control unit which initiates a reactivation cycle each time the systems compressor is initially started. As shown, both the control unit and the compressor motor are powered from the same line 45 and both commence operation in response to the closure of manually operated switch 55. As its timing device the control unit of FIG. 3 includes a motor 56, the output shaft 57 of which is suitably geared to revolve at the rate of one revolution per thirty minutes. Coaxially mounted on shaft 57 of timing motor 56 are a pair of

cams

58 and 59. Cam 58 is substantially circular, but is interrupted peripherally by a sharp valley 60. Cam 59 is essentially a two-phase cam characterized by a raised lobe 61 extending approximately 180 degrees around its perimeter.

Follower rods

62 and 63 ride the rims of

cams

58 and 59, respectively, and operate

make contacts

64 and 65.

Cams

58 and 59 are fixedly secured to shaft 57 such that when motor 56 is at rest, follower rod 62 is positioned in valley 60 and follower rod 63 is at the foot of the leading edge of raised lobe 61.

The motor 56 is connected to line 45 through normally closed break contacts 66 of a thermal switch 67, and the heating element of switch 67 is connected directly across the line electrically behind switch 55. A pilot lamp 50 shunts motor 56 to indicate when the system is operating in a reactivation cycle. As shown, make contacts 64, which are associated with cam 58, are bridged across break contacts 66 of thermal switch 67, and a rectifier 49 in series with solenoid 23 are bridged across motor 56. Make -contacts 65, associated with cam 59, the heating band 12 and its associated bimetallic thermostat 47, all connected in series, are also bridged across the line electrically behind switch 55.

The air compressor is started by closing switch 55, and simultaneously a reactivation cycle is commenced by the introduction of current into motor 56, pilot lamp 50 and solenoid 23 through break contacts 66 of thermal switch 67. Almost immediately thereafter shaft 57 begins to turn

cams

58 and 59, thereby closing ymake contacts 64 and `65. Accordingly, current energizes heating band 12 which begins to transform the accumulated moisture in the desiccant into vapor. Shortly after switch 55 is closed, the heating element of switch 67 causes break contacts 66 to separate. Nevertheless, current is maintained in the motor, the pilot lamp and solenoid 23 through make contacts 64. As in the embodiment of FIG. 2, thermostat 47 maintains the temperature of heating band 12 at a fairly constant level.

After fifteen minutes have elapsed, cam 59 has rotated 180 degrees and follower rod 63 falls, thereby separating make contacts 65. Thereafter, the desiccant begins to cool gradually to a temperature suitable for the drying cycle. At the end of thirty minutes, cam 58 has completed a full revolution and follower rod 62 falls into valley 60. As a result, make contacts 64 separate, thereby deenergizin'g the timing motor, the pilot lamp and solenoid valve 23. In this manner the system shifts from a reactivation to a drying cycle of operation. It will be observed that since switch 55 is still closed after completion of the reactivation cycle, break conta-cts 66 of thermal switch 67 remain separated, and thus prevent the recurrence of a reactivation cycle. However, each time the compressor is started by closure of switch 55, provided that contacts 66 are also closed at this time, a reactivation cycle will be commenced.

Referring now to the apparatus of the embodiments of FIGS. 4 and 5, the same may readily be seen to be structurally similar to the apparatus of the embodiments of FIGS. l, 2 and 3. To this effect, and for convenience of description, corresponding structural components of the apparatus of FIGS. 4 and 5 are identified by the same numerals utilized therefor in FIGS. l, 2 and 3, with the said numerals being primed in the latter figures. Thus, for example, the desiccant 11 of FIG. l bears the identifying number 11 in FIG. 4, while the timing motor 56 of FIG. 3 bears the identifying number 56 in FIG. 5.

By-pass valve 27 is of significantly `different construction in the embodiment of FIG. 4, and comprises a housing 104 connected as shown between connecting pipes 215 and 37', respectively. A stepped bore 105 is formed in the said housing and includes

passages

114 and 116, respectively, extending therefrom as shown for connection with the said connecting pipes. A stepped piston 106, including

piston rings

110 and 112 positioned thereon, and a valve closure member 108 supported therein in the ,depicted marmer, is `slidably positioned as shown within the said bore 105 and is movable therein from the depicted position in which the said valve closure member 108 is effective to prevent fluid ow communication between

passages

114 and 116, to a second position in which such communication takes place whereby connecting pipe 25 is placed in fluid flow communication through the said valve passages with connecting pipe 37 An arcuate cut-away portion 118 is formed as shown in housing 104 just above valve member 108 and functions to enable the pressure in connecting pipe 25 to act upon the portion of the said valve member and piston 106 positioned therebelow. A T-litting 100 is attached as shown to the -outlet of the desiccant chamber 4 by threaded endcap 10 extending thereover, and includes a flow passage 99 formed therein, and a conduit 102 which extends therefrom into uid flow communication with the larger portion of bore 105. Thus may be understood whereby the pressure at the T-itting side of the desiccant chamber 4 is communicated to the larger portion of the said bore.

A housing member 119 is provided and includes communicating

ilow passages

120, 122, 123 and 124, formed therein as shown; with each of `said flow passages being in fluid ow communication with the outlet 149 to the compressed gas utilization device. Check valve 6 is positioned as shown

intermediate flow passages

120 and 122 whereby may be understood that fluid flow therethrough may take place only from the former to the latter flow passage. T-tting 100 is threadably attached as shown to the said housing 119 with flow passage 99 in fluid ilow communication with ow passage 120 to thus provide for the flow of gas from the loutlet of the desiccant chamber 4 to the outlet 149 of the housing 119.

Flow passages 123 and 124 may be seen to provide a by-pass around the said check valve 6', with the latter of the said llow

passages including filters

41 and 42 and disc 40', including restricted orice 49 formed therein, and positioned as shown in the said latter flow passage t-o significantly reduce fluid ow therethrough in either direction.

In operation, with solenoid operated valve 3 deenergized and valve member 16 accordingly positioned as shown, it may thus be understood whereby compressed gas will flow to the said valve from compressed gas inlet 83 through connecting pipe 2', flow therethrough through lopen ports a' and b' thereof, flow through desiccant chamber 4 and through ilow passage 99 in T-titting 100 and flow

passages

120 and 122 in housing 119 respectively, to the outlet 149 to the compres-sed air utilizer. Some of the initial portion of the said compressed gas will of course ow from T-fitting 100 to the larger portion of bore 105 in vhousing 104 to bias piston 106 to the depicted position thereof, whereby valve member 108 will be maintained in the depicted closed position thereof to prevent fluid flow from connecting pipe 25 through the bypass valve 27' to connecting pipe 37.

With the said solenoid operated valve 3i in the energized condition thereof, port a' will be closed by valve stop 18 and ports b and c open and in uid iiow communication. Thus, compressed gas entering at the inlet 83 from the compressor tank will be unable to flow from connecting pipe 2' through the said solenoid operated valve, whereby no appreciable positive pressure will be created in the larger portion of bore 105 of the by-pass valve 27. The compressed gas will, however, ow readily through connecting pipe 25 to fill cut-away portion 118 of bypass valve housing 104 and act upon valve member 108i, piston 106, and piston ring 110, to force the said piston from the depicted position thereof to open valve 108 and place

valve flow passages

114 and 116 in fluid flow communication to allow the compressed gas to flow from connecting pipe 25 through the said flow passages to connecting pipe 37', and to iiow therefrom through iiow passage 125 in housing 119 to the outlet 149 to the compressed air utilizer. Check valve 6 will Y prevent the flow of any of the compressed gas through housing ow passage 122 to housing flow passage 120. A small portion of the gas will, however, flow through passage 123, lters 41' and 112" and orice 49 in passage '124, passage 99 in the T-tting 100, the desiccant charnber 4', and open ports b' and c of the solenoid operated valve, to exhaust to atmosphere from the latter port.

may be understood whereby the drive motor 150 and the indicating light 50' will be energized at all times during the on position of the main power switch 55'. A timing motor 56' is connected between the lines L-ll and L-Z by leads 168 and 162, respectively. Drive shaft 57 extends from the said timing motor and functions, through slip clutch 164, to drive timing cam shaft 163 which includes timing cams 58' and 59' xedly positioned thereon. A positioning knob 166 is axed to the remote extremity of the timing cam shaft to enable the manual adjustment of the positions of the timing cams 58' and 59', without requiring rotation of timing motor 56' due to the action of slip clutch 164.

The windings 23' of solenoid operated valve 3' are connected across the lines by

leads

172, 170 and 160, re-

` spectively. Alternatively, the said windings are connectable across the lines by

leads

172 and 173, timing cam actuated switch 64', and lead 174. Heating band 12' is connectable across the lines by

leads

178 and 179, timing cam operated switch 65', and lead 176. A relay is generally indicated at 179 with the coil 180 thereof connectable across the lines through lead 181, contacts 184 and 194 of the said relay, and lead 182. Alternatively, the said coil is connectable across the said lines by lead 181,

relay contacts

186 and 192, lead 187, lead 179, timer actuated switch 65', and lead 176. A third set of

relay contacts

188 and 189 is connected as shown in lead 160 to control the energization of timing motor 56' therethrough.

The respective timer operated switches and relay contacts are depicted in FIG. 5 in the positions thereof at the commencement of compressor operation. Thus, upon the closing of manually operable switch 55' to energize the said control circuit through lines L-1 and L-2, the circuit to the timing motor 56' will be completed through lead 160,

relay contacts

189 and 188, and lead 162 to thus energize the said timing motor and commence rotation of the timing cams 58' and 59' in the counterclockwise direction as seen in the subject figure. The windings 23' of solenoid operated valve 3' will also be energized through lead 160,

relay contacts

189 and 188, lead 170 and lead 172 to shift the valve member 16' of the said solenoid operated valve from the de-energized position thereof depicted in FIG. 4 to the energized position thereof, whereby port a' will be closed and ports b and c' opened and in fluid flow communication with the atmosphere. Thus, and in the manner described in detail hereinabove, by-pass valve Z7' will be opened and the compressed gas from the compressor tank will commence to flow directly to the outlet 149 to the compressed air utilizer through connecting pipe 25', the now open by-pass valve 27', connecting pipe 37' and housing flow passage 125. A small portion of the gas will also commence to ow through

ow passages

123, 124, 120, and 99, through the desiccant chamber 4' and out to atmosphere through the now open ports b' and c' of the solenoid operated valve. Almost immediately upon the energization of the circuit, and commencement of rotation 0f the timing cams 58' and 59', timer actuated Cil switch 64' is closed as cam follower 62' rides out of cam notch 611'. Shortly thereafter, the high portion 61' of cam 59' will coact with cam follower 63 to close timer actuated switch 65' to thus energize heater band 12' through lead 176, the said timer operated switch 65', lead 179 and lead 178. This will, of course, commence to vaporize the moisture collected in the desiccant 11', in the manner described in detail hereinabove, for the removal thereof to atmosphere through ports b' and c' by the small portion of the compressed gas now owing through the desiccant chamber.

The closing of timer actuated switch 65' will also function to energize coil 180 of relay 179 through lead 176,

the said switch, lead 179, lead 187,

relay contacts

192 and 186, and lead 181. As the relay coil is energized, contacts 188 thereof are opened to thus break one of the energization paths to the said timing motor 56'. The alternative energization path to the said timing motor through switch 64' as described hereinabove remains completed however, whereby the timing motor continues to operate. As the relay coil is energized, this also tends to break

relay contacts

186 and 192 and to make relay contacts 184 and 194, it being understood, however, that relay contacts 184 and 194 are specifically designed to make before

relay contacts

186 and 192 break Thus is made clear that the said shifting of the said relay contacts at this point will have no effect upon the energization of relay coil 18) other than to shift the energization thereof to the path including leads 182 and 181. The apparatus will continue to function in this manner until the low side of timing cam 59' is again presented to switch actuator 63' of switch 65', whereupon the said switch will open to break the energization circuit to the heating band 12 and the said band will commence to cool, while the flow of compressed gas through the desiccant chamber 4' from T-shaped fitting 100 to atmosphere through 4the open ports b' and c' of the solenoid operated valve 3' continues because the said solenoid operated valve remains energized through the continued energization of the winding 23' thereof. Reactivation operation with the heating band 12' de-energized, and cooling, continues until notch 69' of timing cam 58 is again presented to switch actuator 62' at which point switch 64' is again opened to break the remaining energization circuits to winding 23' of the solenoid operated valve 3', and timing motor 56', respectively. Thus the former becomes deenergized enabling the valve member 16 to return to the position thereof depicted in FIG. l, and timing motor 56' comes to a halt. The timing cams 58' and 59' thus halt in the depicted positions thereof. Relay coil 180 remains energized at this time through line L-1, lead 182, relay contacts 194 and 184, lead 181, the coil and line L-2, to thus maintain relay contacts 188 in the open position thereof to prevent further energization of the said timing motor or solenoid valve windings. Thus, it may be understood whereby only the manual opening of main power switch 55' will result in de-energization of relay coil 180 to in turn reclose relay contacts 188 tomake possible repetition of the above described reactivation cycle upon the reclosing of main power switch 55' as described hereinabove.

It will be understood in all cases that the embodiments and arrangements of the invention described herein are merely illustrative, and should not be taken to restrict or limit in any manner the true spirit and scope of the invention.

What is claimed is:

1. A method of operation of a gas drying system, which system includes a source of compressed gas comprising a gas compressor which may be manually started, a gas drying chamber containing a desiccant, and gas utilization means, comprising the steps of: normally passing a relatively large stream of compressed gas from said source through said chamber in a rst direction to said utilization means, whereby said desiccant absorbs moisture from said gas; at intervals, providing a reactivation period comprising discontinuing the fiow of gas through said chamber in said rst direction, heating the desiccant to vaporize absorbed moisture, passing a relatively small stream of compressed gas from said source through said chamber in a second, opposite, direction to a vent, thereby expelling the vaporized moisture from said chamber and said system, and providing, upon demand, a stream of compressed gas from said source, bypassing said chamber, to said utilization means, said reactivation period being provided immediately subsequent to each time that said gas compressor is started and before any gas hom said gas compressor is passed through said chamber in said first direction.

2. A compressed gas drying system comprising compressor means providing a source of compressed gas for a compressed gas utilization device, means providing first and second ducts for alternatively conveying said gas to said device, said first duct comprising a chamber containing a desiccant through which said gas is passed, whereby moisture in said gas is transferred to said desiccant, electric circuit means and valve means operated thereby for concurrently starting said compressor means and blocking said first duct to the conveyance of gas to said utilization device, means for developing a stream of gas when said first duct is blocked, and reactivation means operative when said first duct is blocked to expel said transferred moisture from said chamber, said reactivation means comprising heating means other than the heat of adsorption and operatively associated with said chamber for vaporizing said transferred moisture in said chamber and means for passing said stream of gas through said chamber thereby to exhaust the vapor; said circuit means including a solenoid winding for operating said valve means, and means including a manually adjustable timer and a thermal switch for regulating the heating period, said adjustable timer being also operable independently of said thermal switch to control the energization and deenergization of said solenoid winding.

3. A compressed gas drying system in accordance with claim 2 wherein said timer comprises a timing motor, first and second switches operated by said timing motor, said first switch being operative in conjunction with said valve to block said first duct and said second switch being operative to energize said heating means, a third switch for simultaneously starting said compressor means and said timing motor, and means coupled to said timing motor for operating said first and second switches for different periods of time.

4. A compressed gas drying system comprising compressor means providing a source of compressed gas for a compressed gas utilization device, means providing first and second ducts for alternatively conveying said gas to said device, said first duct comprising a chamber containing a desiccant through which said gas is passed, whereby moisture in said gas is transferred to said desiccant, electric circuit means and valve means operated thereby for concurrently starting said compressor means and blocking said rst duct to the conveyance of gas to said utilization device, means for developing a stream of gas when said first duct is blocked, and reactivation means operative when said first duct is blocked to expel said transferred moisture from said chamber, said reactivation means comprising heating means other than heat of adsorption and operatively associated with said chamber for vaporizing said transferred moisture in said chamber and means for passing said stream of gas through said chamber thereby to exhaust the vapor, said circuit means comprising a timing motor and first and second switches operable to control the energization thereof with said second switch also being operable, in conjunction with said Valve means, to block said first duct, third switch means operable to control the energization of said heating means, and means coupled to said timing motor for operating said second and third switches for different periods of time, and relay means controlled by said third switch means and in turn operable to control the operation of said first switch means.

5. Apparatus according to claim 4 wherein said valve means comprises a multi-port valve disposed in said first duct, said valve having a first port coupled to said source of compressed gas, a second port coupled to said chamber, a third port coupled to an exhaust passageway, and means for alternatively closing said first and third ports; a bypass valve disposed in said second duct having an inlet coupled to said source and an outlet and a third duct connecting said first duct and said outlet of said bypass valve, and serving as said means for developing and passing a stream of gas through said chamber; whereby when said first port is closed said bypass valve is open, and when said third port is closed said bypass valve is closed.

References Cited by the Examiner UNITED STATES PATENTS Re. 18,831 5/1933 Fleisher 55-20 869,731 10/1907 Richardson 137-509 1,620,582 3/1927 Thrush 137--510 1,939,695 12/1933 Hasche. 1,948,779 2/1934 Abbott et al. 55--31 2,058,919 10/1936 Sewell 55-387 X 2,124,932 7/1938 Stark et al. 55--162 X 2,309,075 1/1943 Hill 55-35 X 2,322,603 6/1943 Thumim et al. 55-33 X 2,356,890 8/1944 Schulze 55-62 X 2,440,326 4/ 1948 Gadman 55-179 X 2,494,644 1/ 1950 Clement 55-33 2,535,854 12/1950 Hertrich 188--151 2,600,435 6/ 1952 Shapiro 62--474 X 2,633,928 4/1953 Chamberlain 55--162 2,830,672 4/1958 Asker 55-33 X 2,840,183 6/1958 George 55-309 X 2,955,673 10/1960 Kennedy 55--33 X 2,989,971 6/ 1961 Valentine 137509 X 3,016,978 1/1962 Hull 55-161 X 3,030,798 4/ 1962 Lichtenfels 73-23.1 3,080,693 3/1963 Glass et al. 55-33 X 3,087,112 4/1963 Pfefferle 73-23.1 X 3,147,095 9/1964 Kanuch 55-33 X 3,169,389 2/1965 Green et al. 73-23.1 3,182,435 5/1965 Axt 55-33 X 3,192,686 7/1965 Berkey et al 55--33 X 3,203,771 8/1965 Brown et al. 23-281 3,225,517 12/1965 Wachsmuth 55--80 X FOREIGN PATENTS 857,155 4/1940 France.

Industrol Dynamic Dehumidifiers, Technical Bulletin Number 6551, Industrol Corporation, 472 Westfield Ave., East Rossette Park, NJ., received, Patent Office, Ian. 25, 1962, 2 pages.

Gas Chromatography Growing, Chemical and Engineering News, Apr. 9, 1956, pp. 1692-1696.

Fisher Scientific Company Technical Data Bulletin No. Revised TD-1l4, September 1960, l1 pages.

REUBEN FRIEDMAN, Primary Examiner.

D. TALBERT, Assistant Examiner.

Claims

1. A METHOD OF OPERATION OF A GAS DRYING SYSTEM, WHICH SYSTEM INCLUDES A SOURCE OF COMPRESSED GAS COMPRISING A GAS COMPRESSOR WHICH MAY BE MANUALLY STARTED, A GAS DRYING CHAMBER CONTAINING A DESICCANT, AND GAS UTILIZATION MEANS, COMPRISING THE STEPS OF: NORMALLY PASSING A RELATIVELY LARGE STREAM OF COMPRESSED GAS FROM SAID SOURCE THROUGH SAID CHAMBER IN A FIRST DIRECTION TO SAID UTILIZATION MEANS, WHEREBY SAID DESICCANT ABSORBS MOISTURE FROM SAID GAS; AT INTERVALS, PROVIDING A REACTIVATION PERIOD COMPRISING DISCONTINUING THE FLOW OF GAS THROUGH SAID CHAMBER IN SAID FIRST DIRECTION, HEATING THE DESICCANT TO VAPORIZE ABSORBED MOSITURE, PASSING A RELATIVELY SMALL STREAM OF COMPRESSED GAS FROM SAID SOURCE THROUGH SAID CHAMBER IN A SECOND, OPPOSITE, DIRECTION TO A VENT, THEREBY EXPELLING THE VAPORIZED MOISTURE FROM SAID CHAM-