US2478492A

US2478492A - Ice eliminating system

Info

Publication number: US2478492A
Application number: US428948A
Authority: US
Inventors: Donald M Lawrence
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1942-01-30
Filing date: 1942-01-30
Publication date: 1949-08-09
Anticipated expiration: 1966-08-09

Description

Aug. 9, 1949.

p. M. LAWRENCE ICE ELIMINATING SYSTEM 4 Sheets-Sheet l Filed Jan. 30, 1942 INVENTOR. DONAL D M. LA WRENCE BY I A TTORNEY.

s- 9, 1949. D. M. LAWRENCE 2,478,492

' ICE ELIMINA'I'ING SYSTEM Filed Jan. 30, 1942 4 Sheets-Sheet 2 INVENTOR. DONALD M. LA WRENCE WKW/ A TTORNE Y1 Au 9, 1949. D. M. LAWRENCE 2,418,492

ICE ELIMINATING SYSTEM Filed Jan. 30, 1942 4 Sheets-Sheet 3 g INVENTOR.

DONALD MLAWRENCE ATTORNEY Aug. -9, 1949.

4 Sheets-Sheet 4 INVENTOR. DONALDMLAWRENCE Patented Aug. 9, 1949 ICE ELIMINATING SYSTEM Donald M. Lawrence, Caldwell, N. J., assignor to Bendix Aviation Corporation, South Bend, 1nd,, a corporation of Delaware 'Application January 30, 1942, Serial No. 428,948

11 Claims.

This invention relates to ice eliminating systems, and particularly to a system for removing ice from the leading edges of aircraft surfaces.

Prior to the present invention, it has been common to utilize rubber tubes or boot elements along the leading edges of aircraft wings and tail surfaces in order to break up accumulations of ice on these surfaces and permit the ice to be carried away by the air stream.

In the patent to Gregg, 1,990,866, there is described an ice eliminating system wherein rubber boots are inflated in accordance with a definite cycle of operation, the air from one inflated boot being directed by a distributing valve into a second inflatable boot, until the pressure in the two boots is equalized. Upon equalization of air pressure in the boots, additional air from a pressure pump is directed into the second boot to complete the inflation. The present invention is an improvement over the system described in the Gregg patent, and is directed to a novel air distributing means and method whereby the elimination of ice may be expedited.

In the present invention the distributor valve is so arranged as to flrst'port air under pressure to the selected boot for a first predetermined time interval, then to close on the air pressure and for a second predetermined time interval, controlled by the speed of the motor and by the size of the port opening, to port the air under pressure in the boot to the atmosphere, thereby allowing a portion of the air to flow out of the inflated boot. The valve then closes the port to the atmosphere, and opens a port connected to a source of suction for a third predetermined time interval. This then evacuates the boot and holds it to the airfoil contour. The action of first dumping some of theair from the boot overboard to atmosphere thereby reduces the quantity of air to be forcibly evacuated from the boot through the suction or vent line.

It is an object of the present invention to provide an ice eliminating system for aircraft employing inflatable boot members, wherein the boot is first inflated, then deflated, and finally, placed under suction in separate steps for predetermined time intervals.

. It is a further object of the invention to provide a-system wherein a boot member is subjected to the cycle of inflation to a superatmospheric pressure, deflation to atmospheric pressure, and connection to a source of sub-atmospheric pressure in separate phases.

Yet another object of the invention is the pro- 2 vision of a novel distributing member for carrying out the above novel system.

According to the invention, there is provided a distributor particularly designed for usewith inflatable boots for the elimination of ice from aircraft and adapted when actuated to connect each chamber of a plurality of boot chambers controlled thereby cyclically to a source of fluid pressure, to atmosphere, and to a source of suction, wherein when the pressure source is out OE and the distributor arrested all of the boots are connected to the suction source. The improved distributor may be operative to connect each chamber of a plurality of chambers one after the other to a source of fluid pressure or the atmosphere and all of the chambers simultaneously to a source of suction whereby, when the source of pressure is eliminated, all of the chambers will be evacuated.

Other objects will appear from a study .of the following specification when made in conjunction with the attached drawings, throughout which like numerals designate like parts.

Fig." 1 is a schematic showing in plan of One installation of the system of the present inven-- tion.

Fig. 2 is a view, partly in elevation and partly in section, of the novel distributing valve of the present invention.

Fig. 3 is a cross-sectional view taken along the line 3-3 of Fig. 2.

Fig. 4 is an end elevational view of the distributing valve of the present invention.

Fig. 5 is a perspective of the valve element which is incorporated into the distributor valve assembly of the present invention;

Fig. 5A is an end elevational view of the valve element shown in Fig. 5; and

Figs. 6 and '7 are sectional views of the distributing valve in two different positions in its cycle of operation.

In general, the invention includes the method, and the means for carrying out the method, wherein a boot element is first inflated with air from a pressure source, then deflated to atmospheric pressure, and thereafter, opened to a source of suction for maintaining the bootinteriors at low pressure toprevent boot vibration or boot expansion at low atmospheric pressures.

As shown in Fig. 1, I0 is an aircraft, shown in .phantom, having wing members II and I2, motors 3 plurality of groups of such tubular members, designated I6, I1, I8, I9, 20, 2i, and wing 12 contains corresponding groups Hi to 2!. Each of these groups extends for a definite portion of the wing span. For example, the tubular members in groups [6 and I6 extend to the wing tip, groups 2| and 2| extend inwardly to the fuselage, and each of the other (groups extends outwardly to the next adjacent group. The

additional groups

22 and 22 of tubular members extend along the leading edge of each side of the horizontal stabilizer of the tail portion l5, and another group 23 extends along the leading edge of the vertical stabilizer or rudder post of the tail portion IS. The different wing groups of in flatable members have connection to particular ports of air distributors 24 and -'25-*through air ducts 26, and the different groups of inflatable members on the tail portion have connection to particular ports of an air distributing valve 21 through the air .duetst-Zil. 'si-n'ceiit is impossible to show the ice eliminating system :in true scaled relation to the aircraft 0, the difierent groups or inflatable members which extend along the leading edge f the wings :and the tail surfaces are -.:s'hown as distributed rather largely over the smrface of the Y'Ciiiift, :and the air :ducts .are :repretented-schematically afterthe fashion of anrelectnical *wiring di-a grain.

Engine I:3=id1fives a pressure pump :29'a'nd a suction hump E30, :and engine :14 drives a pressure iprnmp 31 anda suction pump 32. Pumps :29 and 34 :are .'connected through their respective conomits 33 and. :34- to a junction :member '35, from which a single pressure fdistributingwline '36 extends arearwardly of the Junction vmember '35. Pumps and' 32 rare 'jo'ined tosanother portion or junction member 135 through their respective conduits 31 and 38, and a single suction line :39 extends rearward'ly from 'a T ="conne'ctio'n taken .i rom the iroined isuction fconduits 3 and '38. The main pressure line 36 has 'a -"c'onne'ct-ion, which will be better understood :firom :a later -description of the air distributing waives, 'tozthe distributing valves 24 Band sand also a similar connection to the distributin valve 21. Suction line 39 has "connections thefdistributing'valves 25 "and 2;! sin .a manner will also be Eanpa'rerrt :from the later description of the distributor valves.

Earthen, =a ."ch'eckvalve14'0, through which "air :may

be drawn to a low pressure point exteriorly of the plane-:open'sto suction lineal-9.

Particular reference to FEigs. 3 :and '4 should he had for ::a description of the air distributing waives 124., 2 5 and :21. *Since these units are 'basically similar, the'tdescriptionwill he confined to on'e, valve -24. :electric motor -'4'-l which may be driven by the craft power "supply that may be connected to the motor :at the terminal post *42, Ri'ontr'ols the rotation iof a shaft '43 extending within the housing 44 of the distributing valve, ihous'ing c'on tarns speed reduction units, such as a plurality :of worm :and gear drives 45, i'ot'ate the transverse shaft 46=at a suitab'ly slow s eed for the proper distribution of air 'to the inflatable boot members. A igenerally cylindficeil rotatabl'e vane 41, which is cl'early shown in perspective Fig. 5, is oontaine'd "within each of the =distributiirg heads 48 "and 49, and is driven by the tramsverse, double-ended shaft -46, keyed to the last gear or the speed lredu'ction unit 45.

Distributing heads 48 and 49 are identical, and each includes a cyliridric'al body portion =5 I, from which live obliquely extending, radial ports or *boot connections 52 pr'oiec't. Each-of these boot connections is open to a particular rubber boot or series of boots through conventional air tubing, not shown in Fig. 2, but indicated schematically as one of the

tubes

26 or 28 in Fig. 1. Body portion 5i is fitted with an interior metal liner 53, against which the outer surface of the cylindrical valve 47 is rotated by motor 4|. This liner 53, as Well as the body portion 52] {has a lport openin 54 placed under each of the boot "connections 52. Liner 53 also has a single suction connection 55, which opens into a manifold space 56 extending throughout the circumference of body portion 5|. A series of port openings 51, equally spaced about the circumference of liner 53, falls within the marrifoldspace 56 in line axially with the series 'of port openings 54.

Each of the distributing heads 48 and 49 carries an axially extending atmospheric air port connection 58, and this connection 58, along with body portion 5|, is secured to a central housing and standard 59, by means of :a series of studbolts 61i.-

check valve 611 is shown closing a'ir exhaust port 62, and a spring member 63 urges valves 6| closed, although, as will be later shown, airunder certain conditions will cause valve 6! to be swung "about its pivot '54 to open position. The central housing portion '59 contains an air inlet 65, which opens :i-nto distributing heads 48 and 14,59 through circular apertures 66.. V

Considering Fig. 5 along with Fig. '2, it will be seen that valve member 4'! has an end port 61 opening "axially :of valve 4-1, through whichfair under pressure from a pressure :pump may flow from air 'iri'le't '65 to be distributed in the manner that will be described :later. Asecond axial opening 68 is iormed in the outer wall 69 "of valve 41. 'Gpen'in-g *268 forms an air exhaust passagewa :for the dumping of air {overboard to atmosphere through check valve 61' and port connection 58. Three more ports, all opening radially, are contamed in valve 4-1. The largest of these. port openings it, extends axially a sufficient length to establish alt-flow between any two aligned ports 54 and 51 in the liner 53. The next largest 7 port opening M, is axially coextensive with the port openings 54 in liner 53. The last radial opening in valve "41, namely, port opening '12, extends a ally for'thesame d'istance as port opening H,

is 'of considerably less "extent circumferentia lly', as will be pointed -out later. The circumrl erential extent-of each of apertures 10," and I2 bears "a definite relation to each other and to the c'ycleof operatiomwhich consists of the inflation of about, the dumpingof air from'the boot to the atmosphere, and the opening of the boot to the suction pump, which cycle is carried out in one revolution of valve 4 for each of the five boot ports '52.

"Thecycle 'can'be readily understood after considering the rotation of the valve and the distri- '-'bution-ofai'r with respect to one of the boot connections 52, for example, the top boot connection shown in section in Fig-'2. Considering'valve '4 to :be rotated clockwise, as shown in Fig. 5, fpfort opening ll Wi-ll'pass under the top boot conection 5-2 at a fixed speed, depending upon the initial speed. of motor 41 and the train value of the reduction gearing 45. While port opening H is in communicationwith this boot connection 52, air is being admitted under pressure to the boot "connected thereto from the pressure line 36 through the air inlet in connection therewith, and through the ports 56 and 61. As port opening H is rotated past the top boot connection 52, the cylindrical 'sui faceof valve 41 will seal con- 'the distributor line 36. driven

valves

24, 25 and 21 are not in operation which aperture '1 5. nection '52," maintaining the boot inflated until port' opening 12 comes under boot connection 52. For an interval determined by the speed of the valve 41 and the angular size of port opening 12, the air under pressure from the boot will be opened to the atmosphere through port 68, check valve 6| and atmospheric air connection 58. The boot pressure will'there'iore drop until it equals the atmospheric pressure, at which point check valve will close and prevent atmospheric air from entering the boot connection 52. Port opening 12 will have then passed completely out of communication with top boot connection 52, and this connection will be placed in communication with the suction connection 55, which, of

course, is in circuit with suction line 39. During tion of distributor valve '41. r A normal speed of operation may be one revolution of valve 41 in forty seconds, and the port openings 10, H and 12 will be adjusted in size to fit a particular installation of boot elements. It is intended that all boot elements not being inflated through port opening II, or dumped to atmosphere throughport opening 12 and port 68, shall be placed under suction through port and suction connection 55, and therefore, port 10 should be large enough in circumferential extent to place three boots under suction at any one time.

* When the motor-driven-

valves

24, 25 and 21 are'not in operation, all the boot connections are placed under suction. In the arrangementshown in Figure 1 the junction member 35 has connected thereto the pressure conduits 33 and 34 and suction conduits 31 and 38. The junction member 35 includes a suitable gate or control valve for alternately connecting the pressure lines 33 and 34 or the suction lines 31 and 38 to Thus when the motor the valve 35 may be shifted so' as to close or disconnect'the pressure lines 33 and 34 from the distributor line 36 and open or connect the suction lines 3'! and 38 to the distributor line 36. The control valve may be adjusted manually or may be positioned by suitable power means.

, sure, will cause the pressurein line 39 to be maintained at a sulficiently low value to keep the boot elements tightly against the skin of the craft,

thus eliminating the flutter and vibration of boots employed in the conventional system, such as that shown in the Gregg patent above identified. So that the particular boot connection under falls when the system is stopped may be placed under suction, the small slots 13 are provided so that in the "off position,-there may be a continuous sucking of air from the boot connection 52, under which port opening ll stops. In order that the boot connection under which port opening 12 stops may also be open to suction, a small-hole 14, as shown in Fig. 2, is drilled in the wall between port openings H and I2. Slots l3 and opening 14 are so small that during operation of the ice eliminating system, they do not offer substantial interference with the inflating of the different boot members 52, and thus, each of the port openings 10, H and 12 is effectively isolated or chambered from the other two.

The foregoing may also be accomplished by arranging the rotary valve 41, as shown in Figure 6, so that at the opening 12 the rotary valve 41 is spaced slightly from the liner 53 and thereby provides a restricted passage between the rotary valve 41 and the liner 53 extending from the opening 51 to the openings 52 and 12. Thus after the super atmospheric pressure has been exhausted from the connected boot through the valve opening 58 and valve -6l has closed the same, suction may be applied to the boot through the latter restricted passage between the rotary valve 41 and liner 53.

It will be seen, moreover, that if the valve 41 be stopped in the latter position and the super atmospheric pressure be terminated through line 35 without the connection of the suction lines 31 and 38 thereto, then suction may be applied through the restricted passage 14 to port H and slots [3 and the boot connected thereto, as well as to the boots connected to openings 10 and 12.

Thus all of the boot connections may be effectively placed under suction, when the system is not in normal operation.

While only one embodiment of the present invention has been shown in the drawing, it is to be understood that various changes may be made without departing from the scope of the present invention. For this reason, it is intended not to limit the invention by the description herein given as an example, but solely by the scope of the appended claims.

/Vhat is claimed is:

1.' An air distributing device comprising a housing, a cylindrical valve chamber, a rotatable valve therein, said valve having a cylindrical surface, means for rotating said valve, an axially disposed air inlet port to said valve, a plurality of radially disposed boot ports formed in said housing, a plurality of suction ports equal in number to said boot ports and axially aligned therewith, said suction ports opening into a manifold, a suction outlet in communication with said manifold, an axially disposed air exhaust port formed in said housing, a check valve disposed over said air exhuast port and biased. to prevent re-entry of exhausted air, a first valve aperture formed in the cylindrical surface of said valve in registry with each of said boot ports in succession, said first valve aperture being in communication with said air inlet port, a pair of valve apertures, one formed in said cylindrical surface for successive registry with each of said boot ports and the other formed axially for communication with said air exhaust port, a dividing wall formed in said valve for isolating said first valve aperture from said pair of valve apertures, an additional valve aperture in said cylindrical surface, said additional aperture disposed for simultaneous registry with one of said boot ports and one of said suction ports, and means formed in said valve for isolating said additional valve aperture from said air inlet port, from said first valve aperture, and from said pair of apertures.

2. An air distributing device for use with inflatable bootsfor the elimination of icefro-m an 7 aircraft, rcomprising anchousing mailing aevalve -chamber, a'valve; rotatable therein; said, valvebe- Ling. "dividedginto ,three 1 separate compartments,

port, the secondof sai=dcompartments provid;'

: ing separate communication between one of said boot ports and said air..exhaust port, the third ofesaid compartments providing separate communication-between one ,of said boot ports and :saidsuction port: means, and means for rotating said valve toiprovide a predetermined sequence of V aconnections between the boot ports and the other :ports.

J3.,An air distributing device-for use withan inflatable boot: for thebelimination of:ice from ranzaircraft, comprising a housing, a cylindrical valve chamber therein, a cylindrical rotatable valve in said chamber, a'portflo-r connection to said boot, an air inlet port,;an air exhaust port, .andsuction port means in said housing, all opening into said valve chamber, said air inlet and said air exhaust :p-ortsibeing located at opposite ends of said chamber, axially thereof, said valve having one compartment containing apertures registrable with said boot port and. 5&id'fll! in- -inlet ,portga secondcompartment having apertures registrable Withsaidboot and said air exhaust port, a third compartment having an aper- -tureregistrable With said boot port and said suction:portmeansand means for rotating said valve to provide apredetermined sequence of con- ..nections between the boot port and the other ports through said apertures.

4., Ari-air distributing device comprising a housing, .a-cyhndrical valve chamber, a rotatable valve therein, said valve being generally-hollow with a cylindrical valve surface, apluraliw of radially disposed air distributor portsopening into said chamber, suction 'port ,means, .air inlet port 'means and air, exhaust port means opening into "said chamber, a check. valve disposed over said air exhaust port means and biased to prevent re-entry of exhausted air, a vfirst pair of apertures formed in said valve, registrable, .respectively, with one of said air distributor ports and;

said air inlet port, a'second pair of apertures formed in said valve and registrable, respectively, with one of said air distributor ports andsaid air exhaust port means, an additional aperture formed in said valve and registrable, respectively,

with one of saidair distributor potrs and said suction port means, and partition means formed in said valve for isolating said additional aperture from each ofv said pairs of aperturesand said pairs of apertures from each other, and means for continuously rotating said valve so as to effect a predetermined sequence of connections between the air distributor ports and said suction port means, air inlet port means and air exhaust port means.

5. A fluidimedium distributing device for use with inflatable ice eliminating members ior-air- V a craft, comprising a casing, connections'provided on said casing for each of the inflatable members,

a pressure fluid inlet; connection, an atmosphere connection, and a suction connection, a distributor element in the casing, means to rotate the distributor element-said distributor element -operative when rotated toconnect-each inflatable member cyclically with ...the pressure fluid, ,the

iiatmosphere and-thesuction connections, and said rdistributor element including means wherebyupr, on the pressure fluid connection being interrupted and'rotation Of the distributor elementbeing ar- 5 rested .the distributor may connect all of the inflatable membersto a source of suction.

6.,A fluid medium distributing device for use with-inflatable iceeliminatingmembers for aircraft, comprising a casing, connections provided 10 ion saidcasing for each of the inflatable members, a pressure fluid inlet connection, an atmos- :phere:connection, a suction connection, a distributor element, means to rotate the distributor element, thedistributor element including 1151a first compartment adapted to register successively each inflatable member connection with the pressure .fluidconnection, a second compart- 'ment=adapted to register successively eachinflatable member connection with the atmosphere ,connection, and ,a third compartment adaptedto register successively each inflatable member, connection with the suction connection, said distributor element also including means :whereby upon the pressure fluid connection being interrupted and 1 rotation of the distributor .ele-

ment being arrested the distributor may connect alliof the inflatatble members to a source of suction.

'7. A system for the removal of ice from airfoil 3o surfaces of aircraft, comprising, an inflatable ',boot,;flrst means providing a source of a fluid medium under super atmospheric pressure, second means providinga source of. suction, means operable selectivelytoconnect said boot. to, said source ofsuper atmospheric fluid pressureto inflate said boot and to connect said boot .to .atmosphere tordeflate said boot, check valve means to control the atmosphere connection so asto permit gfluid medium under super atmospheric 40 pressure to exhaust from the ,boot, but precluding ;re-entry of .said fluid medium from the atmosphere, and restricted fluid conduit means abeqtweenrsaidiboot and said source of suctiomfor deflating said boot under suction upon said super .45 atmospheric fluid pressure being exhausted from ;said:;boot:through' said atmosphere connection. .8,.,,.A fluid. medium distributing device comprising,ia casing, aplurality of fluid distributor-connections provided. on said casing, a pressure fluid :inlet connection to the casing, an' atmosphere :iconnection to the casing, a suction connection, a distributor element in the casing, means to rotate the: distributor element,- the distributor element including a first compartment adapted to register isuccessively each fluid distributor connection with the pressure fluid connection, a second compartment adapted toiregister successively each of'the fluid distributor connections with the at- -mosphere connection, and a third compartment, a manifold for said casing and havingsuction ports equal in number to and axially aligned with the fluid distributor connections, said suction w-connectionopening into said manifold, 'said third .--compartment 'adapted to successively register Withth-e axially aligned suction ports and fluid distributor connections, and means including a =restricted,passage connecting said first and secondcompartments, whereby upon the pressure Ufluid connectionbeing interrupted. and rotation iof" the distributor element being arrested the distributor element may connect all of'the fluid dis- 'tributor connections to a source of suction.

9. Afluid medium distributing device, comprisring, a casing, a plurality, of fluid distributor con- 7filinectionsrp fovided onsaid casing, a pressure, fluid inlet connection to the casing, an atmosphere connection to the casing, and a suction connection, a distributor element in the casing, means to rotate the distributor element, the distributor element including a first compartment adapted to register successively each fluid distributor connection with the pressure fluid connection, a second compartment adapted to register successively each of the fluid distributor connections with the atmosphere connection, and a third compartment, a manifold for said casing and having suction ports equal in number to and axially aligned with the fluid distributor connections, said suction connection opening into said manifold, said third compartment adapted to successively register with the axially aligned suction ports and fluid distributor connections, and means including a restricted passage connecting said first and second compartments, whereby upon the pressure fluid connection being interrupted and rotation of the distributor element being arrested the distributor element may connect all of the fluid distributor connections to a source of suction, and a check valve in the atmosphere connection for permitting fluid under super atmospheric pressure and returning through one of said fluid distributor connections to exhaust while preventing passage of fluid medium through the atmosphere connection to said fluid distributor connection.

10. A fluid medium distributing device, comprising, a casing, a plurality of fluid distributor connections provided on said casing, a pressure fluid inlet connection to the casing, an atmosphere connection to the casing, and a suction connection, a distributor element in the casing, means to rotate the distributor element, the distributor element including a first compartment adapted to register successively each fluid distributor connection with the pressure fluid connection, a second compartment adapted to register successively each of the fluid distributor connections with the atmosphere connection, and a third compartment, a manifold provided in said casing, said suction connection opening into said manifold, and said manifold provided with suction ports equal in number to and axially aligned with the fluid distributor connections, said third compartment adapted to successively register with the axially aligned suction ports and fluid distributor connection, and means including a restricted communication provided between said first and second compartments, whereby when the source of fluid pressure is cut off and the distributor element is stationary the distributor element may connect all of the fluid distributor connections to a source of suction regardless of the position in which the distributor element comes to rest in its casing.

11. For use with an inflatable element for the removal of ice from airfoil surfaces of an aircraft; a control apparatus comprising, in combination, a unitary housing having an intake port for connection to a source of super atmospheric pressure, an exhaust port for connection to atmosphere, and a port for connection to the element, a valve mechanism in said housing having separate passages connected respectively to said intake and exhaust ports, and said valve mechanism including means operable selectively to connect said element port through said passages to said intake and exhaust ports, check valve means to control the exhaust port so as to permit fluid medium under super atmospheric pressure to exhaust through said exhaust port, but precluding re-entry of said fluid medium from the atmosphere, and restricted fluid conduit means in said valve mechanism and between said element and a source of sub-atmospheric pressure for permitting deflation of said element under sub-atmospheric pressure upon the super atmospheric pressure being exhausted from the element through said exhaust port.

DONALD M. LAWRENCE.

REFERENCES CITED 1 The following references are of record in the file of this patent:

UNITED- STATES PATENTS Number Name ljate 1,825,443 Chormann et a1. Sept. 29, 1931 1,990,866 Gregg Feb. 12, 1935 2,100,154 Ashton Nov. 23, 1937 2,113,253 Gray Apr. 5, 1938 2,217,299 Taylor Oct. 8, 1940 2,233,934 Backhouse Mar. 4, 1941 2,235,138 Billetter Mar. 18, 1941 2,251,430 Taylor Aug. 5, 1941 2,331,580 Slawn Oct. 12, 1942 Certificate of Correction Patent No. 2,478,492. August 9, 1949.

DONALD M. LAWRENCE It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 7, line 32, claim 3, after the Word "boot insert port; line 56, claim 4, for potrs read ports; column 8, line 27, claim 6, for inflatatble read inflatable;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 4th day of October, A. D. 1949.

THOMAS F. MURPHY,

Assistant Oommz'ssioner of Patents.