1. DEHYDRATION APPARATUS COMPRISING IN COMBINATION A COMPRESSOR WITH AN ELECTRIC MOTOR DRIVING IT, HAVING ELECTRIC TERMINALS, ELECTRICAL POWER SUPPLY TERMINALS, A DRYER CONTAINING DESICCANT HAVING AN INLET CONNECTED TO THE COMPRESSOR AND HAVING AN OUTLET, A TANK HAVING AN INLET AND AN OUTLET, THE TANK INLET BEING CONNECTED TO THE DRYER OUTLET, MEANS FOR RETARDING BACKWARD FLOW FROM THE TANK TO THE DRYER, AN ELECTRIC HEATER WITHIN THE DRYER, A PRESSURE SWITCH CONNECTED TO THE TANK HAVING NORMALLY CLOSED CONTACTS ADAPTED TO OPEN WHEN PRESSURE WITHIN THE TANK FALLS BELOW A PREDETERMINED VALUE, A SECOND PRESSURE SWITCH RESPONSIVE TO PRESSURE AT THE OUTLET OF THE TANK HAVING A PAIR OF NORMALLY CLOSED CONTACTS AND A PAIR OF NORMALLY OPEN CONTACTS, THE FORMER BEING ADAPTED TO OPEN THE LATTER TO CLOSE IN RESPONSE TO TANK OUTLET PRESSURE EXCEEDING A PREDETERMINED VALUE, THE SAID ELEC-
Patented Sept. 1, 1964 3,147,095 DEHYDRATHON APPARATUS John A. Kanuch, Cleveland, Ohio, assignor to Great Lakes Manufacturing Corporation, Cuyahoga County, Ohio, a corporation of Ohio Filed Aug. 19, 1960, Ser. No. 50,674 2 Claims. (Cl. 55-163) This invention relates todehydration apparatus and has for its principal object accomplishment of dehydration more efliciently and economically with simpler apparatus.
An object of the invention is to provide a dehydrating system with relatively few components, which will enable dried air to be supplied to a system continuously and which will permit automatic regeneration of desiccant without requiring more than a single dryer or desiccant container.
Still another object of the invention is to accomplish automatic regeneration of a desiccant periodically without requiring timing means.
Other and further objects, features and advantages of the invention will become apparent as the description proceeds.
I In carrying out the invention in accordance with a preferred form thereof, a compressor is utilized having means for controlling its operation. There is a dryer or desiccant container with a vented inlet connected to the compressor and an outlet to a tank, which may be a small tank, with means interposed between the tank and the dryer outlet for restricting backward flow from the tank through the dryer. The tank has an outlet connected to air lines leading to apparatus which require dry air and, if desired, a storage reservoir may be connected to such an outlet line. A check valve is provided in the outlet line of the small tank to prevent loss of pressure from the storage reservoir or from the lines supplying dried air when the compressor is not in operation. Means responsive to the attainment of a pressure exceeding a predetermined value from the outlet side of the check valve is employed for shutting down the opera tion of the compressor, whereby dry air from the small tank flows back at a restricted rate through the dryer for regenerating it during the intervals when the compressor is not in operation.
A better understanding of the invention will be afforded by the following detailed description considered in conjunction with the accompanying drawing in which:
FIG. 1 is a schematic diagram of an embodiment of the invention in which dry air alone is used for regenerating the desiccant of the dryer; and
FIG. 2 is a schematic diagram of another embodiment of the invention in which an electric heater is mounted in the dryer for aiding in the regeneration of the desiccant.
Like reference characters are utilized throughout the drawing to designate like parts.
In the embodiment of the invention illustrated in FIG. 1, there is a compressor 11 delivering air preferably through a cooler 12 and a dryer 13 to a surge tank or purge tank 14 which in turn delivers dry air through an output line 15 in which a check valve 16 and a pressure regulating valve 17 are interposed, preferably a storage reservoir 18 is connected to the dried air output line 15 through a branch line 19.
The dryer 13 consists of a container of desiccant 21 in suitable form. Any one of a number of conventional desiccants may be employed, such as silica gel, activated alumina, or molecular sieve, for example. The dryer 13 has an inlet 22 and outlet means consisting in the embodiment of FIG. 1 of a pair of outlet tubes 23 and 24. The tank 14 likewise has inlet means consisting in the embodiment of FIG. 1 of a pair of inlet tubes 25 and 26. Suitable means are interposed between the outlet means of the dryer 13 of the inlet means of the tank 14 for retarding or restricting the backward flow of air from the tank 14 to the dryer 13 without impeding forward flow. This may take the form of restrictor check valve means. If desired, there may be a separate check valve 27 between the tubes 24 and 26 and a separate re striction or reduced diameter tube section 28 between the tubes 23 and 25, whereby the check valve 27 is bypassed by the restrictor 28 to a limited extent to permit restricted backward flow from the tank 14 to the dryer 13 when the compressor 11 is not in operation.
Suitable means, such as electric motor 2%, are provided for driving the compressor 11. The arrangement is such that the compressor 11 and the motor 29 operate only whenever necessary to maintain the desired pressure in the dry air output line 15. The intervals between operation of the compressor 11 are employed for passing dry air back through the dryer 13 to reactivate the desiccant 21. In this manner only a single dryer is required although dry air is continuously supplied to the system.
In order that the dry air may be passed backward through the dryer 13 the inlet end is vented. This may be done by connecting a vent to the inlet pipe 22 or providing a separate vent pipe 31 at the inlet end of the dryer 13. At the end of the vent pipe 31 there is a vent or opening 32 which may, if desired, form the seat of a normally open vent valve 33. But the invention is not limited to the use of a valve for closing vent 32 and if desired the vent pipe 31 may be provided merely with a restrictor 34 to limit outflow through the vent 32 when the compressor 11 is in operation.
TIT order to avoid building up excessive pressure in the storage reservoir 18 a pressure control device is employed which may take the form of apressure switch 35 having a bellows 36 the interior of which is connected by a branch pipe 37 to the dry air output line 15 with a movable diaphragm 33 carrying a movable contact 39 adapted to cooperate with a pair of stationary electrical contacts 41 forming a normally closed switch which opens when the pressure in the line 15 exceeds a predetermined value.
In the embodiment illustrated in FIG. 1, wherein the vent closing valve 33 is employed in conjunction with an electric control system, the valve 33 is in the form of a solenoid valve having a winding 42 cooperating with an armature or plunger 43 carrying a valve disc or member 44 adapted to close the vent 32 when the solenoid winding 42 is energized.
Although the invention is not limited to the use of a specific form of prime mover for driving the blower, for the sake of illustration, the blower drive motor 29 is shown as being in the form of a single-phase induction motor having motor terminals 45 and 46 adapted to be connected to alternating-current supply terminals 47 and 48.
For simplicity, the contacts 39 and 41 of the normally closed pressure switch 35 are shown as being directly connected in series with the motor terminals 45 and 46 and the electric power supply terminals 47 and 48.
It will be understood, however, that in practice a suit able form of relay means is preferably employed which may take the form of relays, pneumatically or electrically operated, connected in suitable circuit relationship to the motor 29 or to compressor loading valves or the like depending upon the type of compressor control employed. In the arrangement illustrated for simplicity, there is an electric circuit from the power supply terminal 4'7 through a conductor 49, the motor terminal 45, the motor 29, motor terminal 46, a conductor 51, the solenoid winding 42, a conductor 52, pressure switch contacts 3 and 41, the conductor 53, back to the power supply terminal 48. In the arrangement illustrated, it is unnecessary to withdraw dry air from the system supplied by the dehydrator in order to reactivate the desiccant. The purge tank 14 may be a relatively small tank and the use of a storage reservoir 18 and a small purge tank 14 permits the purge tank 14 and the dryer container 13 as well, to be relatively small with frequent re enerating cycles for the desiccant 21.
In the operation of the apparatus of FIG. 1, assuming that pressure in the line has fallen below the value for which the pressure switch 35 is set, the switch closes with the contacts 39 and 41 making electrical connection through the motor 29 and the solenoid 42. The motor 29 rotates operating the compressor 11 with the vent 32 closed. Moist air is received through the intake pipe 54 by the compressor 11 and delivered through the cooler 12 and the dryer input pipe 22 through the dryer 13 passing over the desiccant 21 and out primarily through the check valve 2'7 and the tubes 24 and 26 through the purge tank 14- and a check valve 16 through the output line 15. In passing over the desiccant 21 the moisture is removed from the air so that dry air is delivered at the output pipe 55.
As soon as the compressor 11 has delivered sutficient dry air to raise the output pressure above the predetermined level for which the pressure switch 35 is adjusted, t.e pressure switch opens separating the movable contact 39 from the stationary contacts 41. The motor 29 then shuts down and the compressor 11 ceases operation. The vent valve 33 is also deenergized opening the vent 32. The pressure within the purge tank 14 tends to expel dry air therefrom, out only at a restricted rate through the restrictor 28 since the check valve 27 is closed to reverse flow. The dry air passing through the desiccant 21 removes entrapped moisture and vapor from the dryer container 13 expelling it through the vent 32. Then when the use of dry air supplied through the outlet 55 reduces the pressure below that for which the pressure switch 35 is set, the switch contacts 39 and 41 again close causing the motor 29 and the compressor 11 to operate so that the cycle is repeated intermittently depending upon the demand for dry air in the apparatus connected to the dehydrator outlet pipe 55. The compressor and motor operate only as often as necessary to supply the demand for dry air and no timers are required to accomplish the intermittent regeneration cycle; relatively few valves and other components are required. If the air requirement is very small, the off time of the motor and compressor will be long, thereby increasing the unit life.
Dehydrator systems of the type illustrated are useful in feeding dry air under pressure through the interior of electrical and electronic control boxes in aircraft missiles and other equipment where dry air is essential.
If it is desired to maintain relatively low pressure in the storage reservoir 18, the regeneration action during the oflf time may, if desired, be aided by the provision of a heater in the dryer 13 such as an electric resistance heater 56, as illustrated in FIG. 2. Although a separate circuit may be employed for energizing the heater 56, for simplicity it is shown as being adapted to be connected to the same current supply terminals 47 and 48 as the motor 29.
For controlling the energization of the heater 56, an additional pressure switch 57 is provided which is connected directly to the purge tank 14 and therefore on the inlet rather than on the outlet side of the check valve 16, so that it is not responsive to pressure in the storage reservoir 13, but only to that remaining in the purge tank 14. The pressure switch 57 has a bellows 58 connected to the purge tank 14 and normally closed contacts consisting of a movable contact 59 cooperating with stationary contacts 61, the movable contact 59 being lifted to open a switch 57 when pressure in the purge tank 14 falls below a predetermined value below that for which the output pressure switch 35' is set.
A modified output pressure switch 35 is employed which is of the double throw type having, in addition to the stationary normally closed contact 41, a pair of stationary normally open contacts 62 which close when the pressure in the storage reservoir 18 and the output line 15 increases above a predetermined value for which the switch 35 is set. The dryer resistance heater 56 is included in the circuit of the normally closed contacts 61 and the normally open contacts 62. When the output pressure exceeds a predetermined value causing the movable contact 39 to rest upon the stationary contact 62 an electric circuit is closed from the current supply terminal 47 through conductors 49 and 63, the heater 56, conductor 64 normally closed contacts 59 and 61, the contacts 39 and 62, which are now closed, and conductor 53 back to the current supply terminal 48. The opening of the stationary contacts 41 having shut down the motor 29 and caused the compressor 11 to cease operation, heating of the desiccant in the dryer 13 takes place during the off time when the compressor is not operating and aids in the regeneration of the desiccant caused by the backfiow of dry air from the purge tank 14 through the dryer 13. The heater 56 vaporizes any condensed moisture which may be present in the desiccant and the water vapor is expelled by the pressure from the purge tank 14 through vent 32 which is shown, in this case, as being connected directly to the dryer inlet 22 but sufliciently restricted as not to cause the excessive loss of air when the compressor 11 is in operation.
FIG. 2 also illustrates employment of a unitary restrictor check valve 65 in which the check valve comprises a poppet 66 normally pressed against a seat 67 by spring 68 and the poppet 66 has a small orifice 69 therein which retards the flow of air from the purge tank 14 to the dryer 13 when the poppet 66 is pressed against its seat 67 by the spring 68 upon the fall of pressure from the compressor 11 when it ceases operating.
Certain embodiments of the invention and certain methods of operation embraced therein have been shown and particularly described for the purpose of explaining the principle of operation of the invention and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible, and it is intended therefore, to cover all such modifications and variations as fall within the scope of the invention.
What is claimed is:
1. Dehydration apparatus comprising in combination a compressor with an electric motor driving it, having electric terminals, electrical power supply terminals, a dryer containing desiccant having an inlet connected to the compressor and having an outlet, a tank having an inlet and an outlet, the tank inlet being connected to the dryer outlet, means for retarding backward flow from the tank to the dryer, an electric heater within the dryer, a pressure switch connected to the tank having normally closed contacts adapted to open when pressure within the tank falls below a predetermined value, a second pressure switch responsive to pressure at the outlet of the tank having a pair of normally closed contacts and a pair of normally open contacts, the former being adapted to open and the latter to close in response to tank outlet pressure exceeding a predetermined value, the said electric motor terminals, power supply terminals and normally closed contacts of the second pressure switch being connected in series, and the dryer being connected in series with the power supply terminals, the normally closed contacts of the first pressure switch and the normally open contacts of the second pressure switch, whereby the compressor delivers dry air through the tank until a predetermined output pressure is attained, the motor then being shut down and dry air from the tank traveling backward through the dryer and expelling entrapped moisture through the vent, the dryer heater being disconnected when the pressure in the tank falls below a predetermined value, whereby the remaining air in the storage tank cools the desiccant.
2. Apparatus as in claim 1, wherein a cooler is interposed between the compressor and the dryer inlet.
References Cited in the file of this patent UNITED STATES PATENTS 2,083,732 Moore et a1. June 15, 1937 2,830,671 Robbins Apr. 15, 1958 2,880,818 DOW Apr. 7, 1959 2,955,673 Kennedy et al. Oct. 11, 1960 3,080,693 Glass et a1. Mar. 12, 1963