US2684818A - Control device for inflatable ice eliminating systems - Google Patents

Description

y 27, 1954 H. A. ALEXANDERSON 2,684,818

CONTROL DEVICE FOR INFLATABLE ICE ELIMINATING SYSTEMS Filed Jan. 25, 1951 2 Sheets-Sheet l SUCTION LINE I SUC'IZRELIEF 7 VALVE 6 SEFARATOR 3I ENGINE DRIVEN a AR AIR PUMP FILTER 3 I AIR PRESS. INF 'L-ATABLE BOOTS ll I LINE I 8 29 3o oI T u-rmc. SUCrION LINE I 5% FVALVE AIR PRESSURE LINE/ l5 AlR PIE-E52.

ELECTRIC CONTROL I.INI-:- y 27 3a 25 TIMER 2o ELECTRONIC TIMER INVENTOR. I HOWARD A, ALEXANDERSON -EE I 1 3 g.

HTTO QNE) y 1954 H. A. ALEXANDERSON 2,684,818

CONTROL DEVICE FOR INFLATABLE ICE ELIMINATING SYST Filed Jan. 25, 1951 FIG. 3 /|oo 1 poo EMS INVENTOR.

HOWARD A. ALEXANDERSON Patented July 27, 1954 CONTROL DEVICE F.

ELIMINATI to Bendix Aviation Corporation,

OR INFLATABLE ICE N G SYSTEMS Howard A. Alexander-son, Hohokus, N. J., assignor Teterboro,

J., a corporation of Delaware Application January 25, 1951, Serial No. 207,813

5 Claims.

The present invention relates to an inflatable ice eliminating system for aircraft and more particularly to improvements in such a system including control means for unloading a pressure pump in the system for predetermined periods during the cycle of operation of the system and at a time when the inflating pressure is not required for inflation of the several boot elements of the system. In an inflatable ice eliminating system such as disclosed and claimed in the copending application Serial No. 733,960 filed March 11, 1947, by Donald M. Lawrence and in the Lawrence U. S. Patent No. 2,476,198 granted July 12, 1949, and assigned to Bendix Aviation Corporation, it has heretofore been the practice to operate the pump for supplying the operating pressure for the system under a combined suction and pressure load as shown therein. The suction which may range between 4 and 7 in. Hg is used for holding inflatable boots of the system down and also for instrument operation. Moreover, the air outlet pressure from the supply pump in such an ice eliminating system may range between 8 and 10 p. s. i. and is used for the inflation of the boots of the ice eliminating system.

It has heretofore been customary in the manifold or single main pressure conduit type system,

an unloading valve in a device combining an oil separator, pressure regulator, and unloading valve as disclosed and claimed in the application operating condition, the pump is forced to operate under combined suction and pressure loads. However, in aircraft employing more recently developed high pressure inflatable ice eliminating elements or boots which operate at between and p. s. i., it has been found necessary to remove the suction load from the pump which is supplying pressure to the inflatable ice eliminating system. Also, in some of the lower 8 p. s. i. systems which require operation of the aircraft at high altitudes of, for example, above 20,000 feet; this is also necessary. This has necessitated then the use of separate suction pumps from the pressure pumps for holding down the inflatable ice eliminating boots and for instrument operation.

The main reason for requiring removal of the suction load from the pressure pump in a system of the type disclosed in application Serial No. 783,960 and in the Lawrence U. S. Patent No. 2,476,198 has been the high compression ratio which is encountered at high altitudes and under the high pressure conditions required for operation of the high pressure boots.

For example, a pump operating at sea level under 6 inches of Hg suction load and 15 p. s. i. pressure load operates at a compression ratio of approximately 2.52:1. However, at an altitude of 23,000 feet where the atmospheric pressure is 12.1 in. Hg under the same suction and pressure load the compression ratio is approximately 7:1. Continuous operation at a compression ratio of 7:1 or at even greater ratios at higher altitude involves diiiiculty to the pump due to the extremely high air temperatures effected by operation under such compression conditions which ultimately result in high internal pump temperature and possible failure. Thus, heretofore, it has been found necessary to provide separate suction and pressure pumps for such high pressure systems.

However, I have found that in such inflatable ice eliminating systems, the air under pump pressure during the cycle of operation may be actually utilized for only about half of the cycle of operation and that by unloading the pump during the period of the cycle of operation when the pressure is not actually needed such difiiculties may be alleviated.

Thus, in the present invention, there is provided means whereb additional pump pressure is provided only when actually required by the ice eliminating system during the cycle of operation, while the pressure side of the pump is unloaded to atmosphere during that portion of the cycle of operation when the air pressure is not actually required for inflating the boot.

This arrangement then permits cooling of the pump despite the fact that during the high load portion of the cycle of operation of the inflatable ice eliminating system, the pump is discharging air at extremely high temperatures. Further, through such an arrangement, the average temperature at which such pump may operate is greatly decreased and the pump is conditioned to handle both the suction and pressure sides of the system. This results in elimination of a separate suction source with resulting simplification of the system.

tion of the main supply conduit of the system of say five seconds prior to the period when air pressure will be required for actual operation oi inflatable boots and subsequently maintaining the air pressure in the supply conduit during that portion of pressure is required for inflating the boots and then unloading the pressure from the pump to the atmosphere for the remainder of the cycle so as to permit cooling of the pump during that portion of the cycle of operation of the inflatable boots when the pressure is not actually required for inflation of the boots.

Another object of the invention is to provide control means for a fiuid pump operating under high loads for unloading the pump for short periods of operation when the outlet pressure from the pump is not actually required so as to permit cooling of the pump and decrease in the average operating temperature of the pump.

Another object of the invention is to provide a control device for a combination pressure and suction pump of an inflatable ice eliminating system so arranged as to effect unloading of the pump during the cycle of operation of such a system for short periods when the pressure is not required for inflation of the boots of the system so as to permit cooling of the pump and decrease in the average working temperature of the pump so that the same may handle under high loads both the suction and pressure requirements of the system for operation of the boots.

Another object of the invention is to provide a novel unloading control means for the pressure pump of an inflatable ice eliminating system of the single main pressure conduit type to main: tain the operating temperature of the pump within a safe range-and including means for preventing escape of the pressure medium from the main pressure conduit while the pump is unloaded to atmosphere and control means for effecting the unloading of the pump during the normal cycle or operation of the inflatable elements of the system at such times as the elements .are not being inflated.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example.

In the drawings,

Figure 1 is a fragmentary plan View of an aircraft showing diagrammatically the manner in which the novel control system is connected into the inflatable ice eliminating system.

Figure 2 is a schematic diagram illustrating the control system- Figure 3 is a diagrammatic view illustrating a modified form of the invention.

Figure 4 is a diagrammatic view illustrating a .rotarytimer embodying anothermodified form of the invention.

the cycle of operation when such 'March 11, 1947, by Donald MI.

Figure 5 is a diagrammatic view illustrating a rotary timer embodying a further modified form of the invention.

Referring to the drawing of Figure 1, there is shown an aircraft indicated by the numeral I having an engine 2 and inflatable elements or boots 3 mounted along the leading edge of the lane and of a type suchas disclosed in the copending application Serial No. 733,960 filed Lawrence, U. S. Patent No. 2,475,198 granted July 12, 1949, to Donald M. Lawrence and in U. S. Patent No. 2,515,519 granted July 18, 1950, to Donald M. Lawrence et al. and all of which have been assigned to Bendix Aviation Corporation.

The engine 2 is arranged so as to drive an aircraft propellel 5. An air pump 6 is also driven in a conventional manner by the engine 2 and has provided a suction conduit 1 leading to the main suction line 8 through a suitable suction relief valve, as shown.

An air pressure line 9 leads from the pump 6 to the inlet of a pressure unloading valve ordevice indicated generally by the numeral l0 and which may be of the type disclosed and claimed in the aforementioned application Serial No. 733,960. The air passes through the device It] and into the outlet conduit l2 upon energization of a control solenoid provided therein as explained in the application Serial No. 733,960. During the passage of the air through the device as, any particles of oil which may enter the air from the pump 6 or other source, is separated and the air is filtered of dirt and other extraneous matter by an oil separator and air filter provided in the device H] as disclosed and claimed in the U. S. application Serial No. 733,960. The air flow thus processed, is conducted through the conduit 12 to the air pressure line l5.

The suction and air pressure lines 9 and I5 lead to suitable air distributor valves 18 which are electrically controlled by a timer indicated generally by the numeral 20 so as to operate the inflatable boot elements 3. A plurality of such distributor valves are preferably provided of a type such as disclosed and claimed in the aforenoted U. S. Patent No. 2,515,519. The timer 20 includes as shown in Figure 2 an electronic timer which may be of the type disclosed and claimed in U. S. Patent No. 2,444,210 granted 'June 29, 1943, to John W. Lauricella and assigned to Bendix Aviation Corporation. The operation of the timer is described in detail in the U. S. Patent No. 2,444,210.

A manually operable switch 25 is arranged to' control the operation of the timer 2!, as will be readily apparent, through electrical conductors 29 and 21 leading from a source of electrical energy 28, while operation of the unloading valve mechanism of the device I!) is controlled by a solenoid dependent upon subsequent operation of the timer 2!, as explained hereinafter.

In the control system of the application Serial No. 733,960, the closing of the switch 25 simultaneously closes both circuits 26-2? and 2030 to eflect operation of the timer 20, as well as cause the unloading valve of the device iii to direct air under pressiu'e through line i2 to the pressure line I5 so long as the timer 10 remained in operation. In the system disclosed in the latter application, when switch 25 was opened and operation of the inflatable ice eliminating system terminated the unloading valve of the device It! would close-the conduit l2 and direct the air flow from the conduit 9 to an over-boarddumpdl, as

explained in the application Serial No. 733,960.

In the present invention, the circuit Mi-30 controls a corresponding unloading valve in the device l6 through a solenoid indicated diagrammatically in Figure 2 by the numeral 33. The unloading valve and solenoid 33 of the device may be of the type disclosed and claimed in the application Serial No. 733,960 in which the urn loading valve is arranged to close the passage l2 and open the passage 3| to the passage 9 upon deenergization of the solenoid 33, and close the passage 3| to passage 9 and open the passage |2 to the passage 9 upon energization of the solenoid 33.

As shown in Figure 2, the control circuit 29-30 is opened and closed during the cycle of operation of the inflatable ice eliminating system in timed relation with the period of inflation of the several boots of the system.

Thus, during the cycle of operation of the inflatable ice eliminating system the suction-pressure pump is unloaded to atmosphere during that part of the cycle of operation when pressure is not required for inflation of the boots of the system so as to permit cooling of the pump and operation of the pump under high load conditions.

Referring to Figure 2, there is shown a shaft 35 indicated by dotted lines for driving switch arms 36 and 31 from a stepper relay mechanism. The stepper relay mechanism is not shown herein, but is provided in the Electronic Timer mechanism 2| and may be of a type such as disclosed and claimed in the U. S. Patent No. 2,444,210.

The switch arms 36 and 31 are each arranged to contact in succession a series of contacts 36A-L and 31A-L. The switch arms 36 and 31 move in a clockwise direction from one contact to the next succeeding contact in a step by step action imparted through shaft 35 by the stepper relay of the Electronic Timer 2| and upon one end of the switch arms 36 and 31 moving out of contacting relation with the contact L the opposite end closes the contact A.

As explained in the U. S. Patent No. 2,444,210, upon cessation of operation of the timer 2| the stepper relay will return the switch arms 36 and 31 to the starting or L position and will continue to adjust the switch arms 36 and 31 in the step by step action until operation is terminated.

The switch contacts 36B-36G are connected respectively through suitable electrical conductors 38 to one terminal of corresponding control solenoids 39.

The opposite terminals of the solenoids 39 are connected by an electrical conductor 40 to the negative terminal of the source of electrical energy 28 through a grounded connection.

The control solenoids 39 serve upon energization to open respective boot inflating valves in the air distributingvalves |8 as disclosed and claimed in Lawrence 2,515,519.

The switch arm 36 is connected by a conductor 43 through the control switch 25 to the positive terminal of the source of electrical energy 28. The contacts 36A and 36H-36L are open contacts so that upon the switch arm 36 contacting the same the circuit to all of the control solenoids 39 are open and operation of the inflatable boot elements is not affected during the periods that these contacts are closed by the switch arm 36 and during the cycle of operation of the inflatable ice eliminating system.

The switch arm 31 is connected by a conductor et al. U. S. Patent No.v

45 through the switch 25 to the positive terminal of the source of electrical energy 28 and is arranged to sequentially close contacts 31A-31G which contacts are connected through the conductor 29 to the control solenoid 33 of the unloading valve of device ID. The opposite terminal of the control solenoid 33 is connected through conductor 36 to the negative terminal of the source of electrical energy 28. The contacts 31H-L corresponding in position to the contacts 36H-L are open contacts. Thus, when the switch arm 31 closes one of the contacts H-L the control solenoid 33 is deenergized and the pressure from the pump 6 is directed by the unloading valve 0 to atmosphere through the exhaust conduit 3| rather than through the pressure conduit I 2. However, upon the switch arm 31 closing one of the contacts 31A-G, the solenoid 33 controlling the unloading valve |0 is energized causing the unloading valve In to connect the pump 6 directly to the pressure conduit l2 and closing the connection of the pump 6 to atmosphere through the conduit3 I.

The electronic timer 2| as explained in the U. S. Patent No. 2,444,210 controls through adjustment of shaft 35 the period of time that the switch arm 36 rests on the contacts 36AL as well as the period of time that the switch arm 31 rests on the contacts 31A-L. Thus, the electronic timer 2| controls through the distributor valves 8 the periods of inflation of a series of solenoid controlled inflatable elements or boots 3 for preventing the accumulation of ice on or the removal of ice from airfoil surface of the aircraft as well as controlling in timed relation therewith the period of energization of the solenoid controlled unloading valve l0.

It will be seen then that in the operation of the improved control system forming the subject matter of invention herein that as the switch arm 31 closes contact 31A and thus aiiects the energization of the unloading valve control solenoid 33 so as to direct the pressure of air from the pump 6 into the pressure conduit l2 a switch arm 36 will simultaneously close the open contact 36A. The arms 36 and 31 will rest on the respective contacts 36A and 31A for a short period of time determined by the electronic timer 2| of for example five seconds, sufficient to assure full inflating pressure in the line l5 before the closing of contact 33B by the switch arm 36 for eifecting the inflation of the first boot 3 of the ice eliminating system. The control solenoid 33 of the unloading valve I0 is kept energized by the successive closing of contacts 31B-G by the-switch arm 31 during the successive inflation of all of the several boot elements controlled by the switch contacts 36B-G. However, upon the switch arm 36 moving from contact 36G to contact 36H and the switch arm 31 moving from the contact 31G to contact 31H the control solenoid 33. will be deenergized causing the unloading valve Hi to connect the pressure outlet 9 of the pump 6 to atmos phere through the conduit 3| while closing the passage |2 so that the pump 6 will now operate without the pressure load during each of the time periods of closure of the contacts 36H-L and 31H-L by the switch arms 36 and 31, respectively. During the latter period of the cycle of operation of the inflatable ice eliminating boots the pump 6 serves only as a suction pump, while during the periods when the switch arm 31 closes the contacts 31A-G the pump 6 serves the dual function of a suction and pressure pump for the ice eliminating system.

However; by permitting the-pump;;6 to unload to atmosphere -.during aiportionof, .the.- cycle of,

to. handle: both the suction and 4 pressure sides of thee-system during -the cycle. of. operation;

Modified formof Figure 3 In Figure 3, there :is'. shown diagrammatically amodified form of, electrica1:timer for operating. suitable. control .5 solenoids or .eleictromagnets I of. the pressure distributing valve -.I 8 ;of .Figure 1 and. which valves may .be of thetype disclosed and claimed: in the Lawrence :etv :al; 1U. S. Pa-tent NO."-2,515,519 granted-July 18,2195!) ;and-.-assignedtowBendixjnviatio-n Corporationr.= Corresponding numeralsare usedin Figure 3 to indicate like parts to those previously shown. and described .with reference: to, Figure .1.

As. shown in Figure-3, :a controlcircuit is provided ;.for .the .electromagnets III II which circuit includes a timer indicatedxby. thexnumeralultl; The timer: I0l;is ofthe rotary type zsuch as disclosedandclaimedinthe-Lawrencelet .al. U, S; PatentpNon 2,515,519 and. comprises a notary arm I02 ;-driven;;by:an ;ele;ctric.=motor 'I03 .through a shaft-103A. so as. :to openand close in; sequence control. contacts indicated .by' thenumera-l. I M'A-J to selectivelyocontrol the-.zenergizationzof.electroe magnets I00 The control-contacts I I 04A-J as shown ;.in 1 Figur.e ;3, varyzinisize :so. :that the pe1iod.:of energi zation of. each-10f the .said electromagnets; I 00 will; be in proportion;..to the; timev interval re-. quired ;-to properly inflate-the respective :inflatable elements or boots loontroll'ed thereby swhich time. interval. mayberbased upon the; proportionate capacity oithe. respective elements; The inflatable elements-are indicated generally inp-Figa ure .l-by thenumeral 3.

The: rotary arm I02 ;a1s'o.moves-.imcontacting relation-along. a :conductor ring :10 5,: which electrically nonnects. therarma .1I 0.2:,?:through.:an 'elec-. trical conductor -I 01., to, one terminal of a .suitable. source of electrical energy 108.: Aswitch I09 isarrangedto open and .close. the.;oircuit to the source of electricahenergyi0.8;-.-. Thenppo-r site :terminal: of the source: .of; .ielectricalz.ienergy I03 :is grounded; as shown; in "Figure. '13.

Thus,-, upon theaswitch I03 being closed, the arm: I 02 on contacting. one of the contactsj 0.dA.-iJ will close a circuit. to the electromagnet I tllucone trolled thereby, causing a flow of electricalenergy to pass through the switch! 09,;conduitd 0.1; iring I05;,-.;arm -l02-,-the contactIIMAeJ closed thereby through the=e1ectromagnet- I00-connected to the closed circuit, and returning, .through.;.. the grounded connection. of the. electromagnet; :I 00, as shown, to the grounded opposite.:-.terminal of the source of electrical--.energy-.;I08."

Thus, the closing; of any .;one of: the; contacts I MA-J will causeethe. energiza-tionfif' the corresponding. electromagnet I00 connected to v.zthe closed. circuit :for-efieoting ;:.the. operation of the distributor valve. .I 8 controlledthereby, as- :described'in the Lawrence; et-aL :U.;S. PatentvNo. 2,5l,5,519..-.

The rotary arm- -.I this further arranged toopen and .close an-additionalsegmental conductor ring contact :I I0. which is mounted astshown inFigure 3 together.withtheconductor ring lod andcontacts. I. I Mion a basenplateil I2 ,formedoi-a -suit+ able. electrical..insulating materialm The-.niotor I03 rearranged. to drive therotary armdIIZdn-a counter-clockwise direction and the contact I I 0 issoa-rra-nged in relation to the contacts IMA-J that-thearm I02. first. closes the contact H0 before closing the contact .IMA.

I The contacts IS IA-IJ. are arranged in spaced relation on the base plate I I2 so that as the arm I02 passes .from one contact It IA-J to the next succeeding. contact the-arm IE2 rests for a relativelyshort interval or" time out of a contacting relationwithany of. thecontacts III lA-J,

However, in the form or" the invention illustrated in Figure 3,.the rotary arm I02 continues to close-the. contact Iit after the initial closing thereof until the rotary arm Hi2 has been driven by the motor. I03to a position opening contact IEI IJ, at. which positionthe arm I02 simultaneously .opens both contact ltd-J and the contactv H0 after which the rotary switch arm I02 remains in circuit open relation'to the contacts I0 IA-J- and I I0 until theirotary arm I 02 isdriven by themotor I03 sotas to once againclose contact. II0.

Thencontact -.I I0 isconnected by aconductor II I tozonesendofan electromagnetic winding or solenoid I I5 Whichisconnected at its opposite endto agrounded-conductor. The electromag-, netic winding IIII contro'is operation of a pressure unloading .valvemechanism indicated generally bynthe numeral -ll and which may be of the=type disclosed andclaiined in the aforementioned U. S. Patent No. 2,4=76,198 or of the type disclosedand claimed in application Serial No. 733,960 filed March 11; 1947, and assigned to Bendix Aviation Corporation or may boot the type shown diagrammatically in Figure 3.

The pressure unloading valve mechanism I0, as indicated diagrammatically in Figure 3, includes a chamber I III into :whioh'opens the pressure conduit 9 leading from the air pumpii. A discharge passage I253 opens from the chamber IIE into the discharge conduit 3! opening to atmosphere, while anoppositely disposed passage I22. opens fron1.the-..chamber IIE into anseco-ncl chamber I24 formed in the mechanism-I0. The chamber: I I8 is sepa-rated .from the chamber I25 by a partition-126.. As showninFi-g-ure :3,:the conduit I2- .leads-iromthe chamber-.124 and :to the-main-pressure-conduit It as shown in Fig urell...

Controlling the opening of the passages I20 and I272. -from-the-:chan1ber IIS a valve I23 whichcooperates-withthe open end of the passages-IZIiandI-IEZ .-so..as .to openone while closing the other and thereby permit the passage of air under-.pressure-irom the pump either to the atmosphere-through the'passage IE0 or to the main air pressure conduit I5 through the pas: sage I22; chamher'IZe andconduit I2; Astem ltd-controlling the valve I25 is slidably mounted in theipassage I22 by a bracket I32. Stem I30 is affixedto a flexible diaphragm member I34 and is normally biased by spring Ifit so as to close the passage I22 while opening passage I20 The electromagnet I I6, as shown diagrammatically in Figured; directly controls the valve stem I3Ii-solthat uponienergization of the electromagnet H6 theiva'lve I28 is biasedin opposition tothe-spring ;I3 to close passage I20 and open-passa e,-.-I22 and thereby direct air vfrom the-pump 5 to the pressure conduit I2 through the chamber-J24. Upon deenergization-of the'electromagnet-l IJS the valve I23 is biased by the spring-;,I3tv so: as to. close the passage 1 I22 preventing the air pressure in-line I5 fromleaking etoaatmosphere through the device I0, rwhile-permitting the pump 6 to unload to atmosphere as heretofore explained.

While the valve mechanism I is preferably of the form disclosed and claimed in the Lawrence application Serial No. 733,960 in which there is provided a control solenoid to operate the valve I28 through a pressure servo mechanism and means providing a pressure regulating action of the valve I28 in addition to the control action heretofore explained, the invention herein disclosed and claimed is not limited thereto and may include a pressure unloading valve mechanism of the type such as shown in the Lawrence U. S. Patent No. 2,476,198 granted July 12, 1949, or a pressure unloading valve mechanism of a type in which the valve mechanism is arranged to alternately unload the pressure side of the pump to atmosphere or connect the pressure side of the pump to the main air pressure line for providing a suitable supply of air under pressure for. operating the several inflatable elements or boots of an ice eliminating system as heretofore described with reference to Figure 3.

As further shown in Figure 3, the rotary arm I02 of the timer IIJI is driven by the shunt motor I 03 energized by a suitable source of electrical energy indicated by the numeral I40, such as an aircraft motor driven generator, battery, or other suitable means. A switch MI is provided for controlling the motor circuit.

There is further connected in a variable resistance I 42 whereby the speed of rotation of the motor may be varied as described in the Lawrence et al. U. S. Patent No. 2,515,519. It will be seen that by varying the speed of rotation of the motor I03 the period of inflation of each inflatable ice eliminating element or boot may be proportionately increased or decreased with the variance of the speed of the motor. Thus, as explained in the U. S. Patent No. 2,515,519, there is provided convenient means whereby the period of inflation of the inflatable ice eliminating elements may be varied so as to compensate for changes in icing conditions. Thus, under relative hard ice conditions the motor I03 may be driven at a relatively slow rate of speed so as to increase the inflation period, while under slushy or soft ice conditions the more rapid inflation and deflation of the inflatable elements may be effected by increasing the speed of the motor I93 through adjustment of the variable resistance I42. The more efiicient ice removal may thereby be effected.

It will be seen then that in the operation of the modified form of invention shown in Figure 3 that as the rotary switch arm I02 closes contact III) and thus effects energization of the unloading valve control electromagnet I I6 so as to direct the pressure of air from the pump 5 into the pressure conduit I2, the inflating pressure in the conduit I2 will be conditioned for the subsequent closing of the contact IMA so as to assure sufiicient pressure for inflating the boot controlled thereby. The rotary switch arm I02 may rest on the contact IIfl for a short interval of, for example, five seconds prior to the closing of contact IEMA and sufficient to assure full inflating pressure in the line I5 before the closing of the contact IMA by the switch arm I02 for effecting inflation of the first boot 3 of the ice eliminating system. The control electromagnet N6 of the unloading valve I0 is completely energized by the closure of the'contact III) by the switch arm I02 during the successive closing of contacts IMA-J by the switch arm I02 and during the motor circuit of the unloading valve II) will now connect the pressure outlet 9 of the pump 6 to atmosphere through the conduit 3|, while closing the passage I22 so that the inflating pressure in line I5 may not escape and the pump 6 may now operate without the pressure load during the period of time when the rotary arm IE2 is driven by the motor 23 between the open ends of the contact II 0. During the latter period of the cycle of operation of the inflatable ice eliminating boots the pump 6 serves only as a suction pump while during the period when the rotary switch arm I02 closes the contact I II], the pump 6 serves the dual function of a suction and pressure pump for I the ice eliminating system.

However, by permitting the pump 8 to unload to atmosphere during a portion of the cycle of operation of the inflatable ice eliminating systern, the average working temperature of the pump 6 is greatly decreased and the pump 6 is enabled to handle both the suction and pressure 7 side of the system during the cycle of operation. Modified form of Figure 4 While in the form of the invention shown in Figures 1 and 3, there is provided means for connecting the pump 6 to the pressure line for a short period of five seconds prior to inflation of any of the inflatable elements 3 so as to assure that full inflating pressure is provided in the pressure line I2, it will be seen that this safety provision may be disregarded provided that the pressure unloading valve I28 of the mechanism I0 sufiiciently closes the conduit I2 to atmosphere to prevent escape of the inflating pressure in the main pressure line I5 during the period of time that the pressure conduit 9 of the pump 6 is unloaded to atmosphere.

In the latter event the safety provision of providing a short period of pre-inflating pressure be eliminated and the timer IOI may well take the form shown in Figure 4 in which the contact I IDA may be simultaneously closed with the first control contact I 04A. Operation of the timer in the form of invention shown in Figure 4 is otherwise the same as that heretofore described with reference to the invention shown in Figure 3 i and like numerals on Figure 4 indicate corresponding parts to those heretofore described with reference to the form of invention shown in Figure 3.

Modified form of Figure 5 A further form of the invention is shown by' Figure 5, in which successive contacts I IflA-I IOJ are opened and closed by the rotary arm I 92 simultaneously with the opening and closing of value for operating the several inflating boots at such times as any one of the contacts IMA- IMJ are closed, while at such other times as the arm I02 moves oil of the contacts I MA to IIMJ and contacts IIOA to IIOJ deenergization aes' iysrs of 'theelectfomagnet'or' solenoid '5 it will cause van/e123 to un1oad"the'pump"5'to atmosphere while closing the passage I22 so as to prevent escape of "the inflating pressure in the line l5.

Byt-hus permittingthe pump 5 to unload to atmosphere'during a portion'of the cycle of operation'of the inflatable ice eliminating system the average working temperature of the pump may be "decreased and the pump enabled to handleboth the suction and pressure requirementsof the system during the cycle of operation.

It will be seen'from the foregoing that the present inventionprovides novel means for controlling the unloading of'a'pressure pump of an inflatable ice eliminating system'of the manifold or""sin'gle main pressure: conduit type disclosed in'the' Lawrence'et al. S. Patent No. 2,515,519 and includes valve'mea'ns for preventing the escap'e'of back pressure fromithe main pressure conduit while the pump is unloaded'to atmosphere,"together with novel'control means for such valve means for effecting the unloading of the pressure pump to atmosphere during the normal cycle of operation'of the inflatable elements of "the system "at timed intervals and at such times as the "elements are not inflating. The invention'may be applied'tosuch an inflatable ice eliminating system to' provide" control means for periodically unloadingthe pressure pump to atmosphere for coolingthepump' and maintaining the average Working temperature of the pump within a safe range under'high pressure operating conditions and may be applied to such a system in which the pressure pump provides a source. of. suction, as well-as. to such a system in which a separate source of suction ornegative pressure is provided for completely deflating the several ice eliminating elements ofthe system.

Although-.onlyseveral embodiments-of the in vention-havebeen illustrated an'd described variouschanges of-theform and relative arrangements-ofthe parts may be made to suit requirementsr What is claimed is: U

1. For-use in a system=for the removal of ice from; anaircraft having a plurality of inflatable units, a pumpto supply-a pressure medium for inflating saidcunits, a plurality of distributor valves for controlling the pressure medium from said pump to' inflateand-deflate said-units, and an independently operable valve for unloading the pressure mediumfrom said pump to atmosphere;,the combination comprising means for controlling operation of said distributor valves, a timing device operativelyconnected to said control-means in such a manner as-to cause operatiori of said distributor valves so as to selectively inflate and deflatesaid units and to maintain all of said units in a' defia ted'condition for a predetermined interval of time, means for controlling operation of said unloading valve, means operatively connecting-the timing device to said last-mentioned control means to cause operation of said unloading valve -in relation to the operation of said. distributor valves so as to prevent the unloading valve from unloading the pressure medium from the pump during the inflation of the inflatable units and effect the unloading of saidpump for at least a .part of the predetermined interval of time during which all of the units are maintained insaid-deflated condition.

2. For use in a system for the removal of ice from an. aircrafthaving a plurality of inflatable units, a'pump to supply a pressure medium for inflating said units, aplurality. of" distributor valvesfor controlling the pressure medium from said pump to inflate and deflate "said units; and. an independently operable valve forunloading the pressure medium from said pump to"a tmos' phere; the combination comprising a plurality of electrical contacts for selectively controlling" operationof the distributor mechanisms and electrical contact means for controlling operation" of the'unloading valve, switchi'arm"meansi'ior selectively cooperating .with said" contacts and electrical contact means, a'motor, said switch arm means being adjustably positionedjrelative to said el ctrical centacts'and contact means by said motor, said plurality of contacts being opened and closed by said'switch arm "means to effect selective operation of'the'distributor mechanisms in such a manner as to selectively: inflate and deflate said units and to maintain all of said units'in adeflated condition for a pre-' determined interval 'of' time, and said contact unloading valve from unloading the pressure medium from the pump during the inflation-of" the inflatable units and efiect' the unloading of said pump for at least apart of 'the'predetermined interval of. time during'which all of the units are maintained 'in' said deflated condition. For usein a system for the removal of ice from an aircraft having a. plurality of inflatable units, a' pump to supply a'pressure mediumifor" inflating said units, a plurality. of" distributor valves for controlling the pressure medium from said pump to inflate 'anddeflate said units, and

an independently operablevalve for unloading the pressure medium from'saidfpump to at mosphere; the combination comprising a flrst'set of electricalcontacts for selectively controlling operation of fthe distributor" mechanisms and a second set of electrical contacts for controlling operation of the unloading valve; switch arm means for selectively cooperatingwith said first and'seccnd sets of contacts; a motor, said switch arm'means being adjustably'positioned relative" to said contacts said motonsa-id first set .of contacts being opened and closed by said switch.

arm means to effect selective operation ofthe distributor mechanisms in such a manner as to i selectively inflate and deflate said units and to maintain all of saidunits in a deflated condition for a'predetermined interval of time, andsaid second set of contacts being simultaneously opened and closed by the switch arm means with. the contacts of the first set so as to prevent said unloading valve from unloading the pressure medium from the pump during the inflation of the inflatable units'and :effect the unloading of said pump for at least apart of the predetermined interval of time during which all of the units are maintained in saidfdefla ted' condition.

4. For use in a system for thelremoval of ice irom'an'air'craft having a plurality of inflatable units, a pump to'supply a pressure mediumfor inflating, said units, a plurality of distributorvalves for controlling the pressure medium from said pump to inflate and deflate sa-id units, and an. independently operable valve for unloading the pressuremedium from said'pump-to atmcsphere; the combination comprising an electrical contact means including a plurality of contacts for selectively controlling-operation -of.=the distributor mechanisms and an additional contact for controlling the unloading valve, switch arm means for selectively cooperating with said contacts, a motor, said switch arm means and said contacts being adjustably positioned relative one to the other by said motor, said plurality of contacts of said contact means being opened and closed by said switch arm means to effect selective operation of the distributor mechanisms in such a manner as to sequentially inflate and deflate said units and to maintain all of said units in a deflated condition for a predetermined interval of time, and said additional contact being closed by the switch arm means immediately prior to the closing of the first of the contacts controlling the distributor mechanisms so as to prevent the unloading valve from unloading the pressure medium from the pump during the inflation of any one of the inflatable units and to assure that full inflating pressure is provided during the sequential inflation of the inflatable units.

5. For use in a system for the removal of ice from an aircraft having a plurality of inflatable units, a pump to supply a pressure medium for inflating said units, a plurality of distributor valves for controlling the pressure medium from said pump to inflate and deflate said units, and an independently operable valve for unloading the pressure medium from said pump to atmosphere; the combination comprising an electrical contact means including a plurality of contacts for selectively controlling operation of the distributor mechanisms and an additional contact for controlling the unloading valve, switch arm means for selectively cooperating with said contacts, a, motor, said switch arm means and said contacts being adjustably positioned relative one to the other by said motor, said plurality of contacts of said contact means being opened and closed by said switch arm means to effect selec tive operation of the distributor mechanisms in such a manner as to sequentially inflate and de nate said units and to maintain all of said units in a deflated condition for a predetermined interval of time, and said additional contact being closed by the switch arm means simultaneously with the closing of the first of the contacts conrolling the distributor mechanisms so as to prevent the unloading valve from unloading the pressure medium from the pump during the inflation of any one of the inflatable units and to assure that full inflating pressure is provided during the sequential inflation of the inflatable units, and said additional contact being simultaneously opened by the switch arm means with the opening of the last of the plurality of con tacts controlling the distributor mechanisms so as to permit the unloading valve to unload the pump to atmosphere upon termination of the period of sequential operation of the inflatable units.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,444,208 Taylor et al June 28, 1948 2,444,210 Lauricella June 29, 1948 2,476,198 Lawrence July 12, 1949 2,515,519 Lawrence et a1 July 18, 1950

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