US2692743A - Means for distributing deicing liquids on surfaces subject to ice-formation - Google Patents

Description

Oct. 26, 1954 c. c. 5. LE CLAIR MEANS FOR DISTRIBUTING DEICING LIQUIDS ON SURFACES SUBJECT TO ICE-FORMATION Filed Jan. 25, 1949 3 Sheets-Sheet l Attorneys.

I nvenIor Oct. 26, 1954 c. c. 5. LE CLAIR 2,692,743 MEANS FOR DISTRIBUTING DEICING LIQUIDS v ON SURFACES SUBJECT TO ICE-FORMATION Filed Jan. 25, 1949 3 Sheets-Sheet 2.

Attorneys.

c. c. 9. LE CLAIR MEANS FOR DISTR Oct. 26, 1954 2,692,743

' IBUTING DEICING LIQUIDS 0N SURFACES SUBJECT TO ICE-FORMATION 3 Sheets-Sheet 3 Filed Jan. 25. 1949 w 47 F/G. /4.

5G F 6. l8.

1 Invenlo r metal powders.

Patented Oct. 26, 1954 YUNITED STATES PATENT OFFICE .MEANS, FOR DISTRIBUTINGTDEICING LIQUIDS ON SURFACES. SUBJECT TO ICE-FORMATION Claims priority, application'Grea-t- Britain February 6, 1948 12 Claims. (01. 244-134) This invention relates to liquid distributing -means for use in distributing on surfaces subject to ice-formation de-icing liquids which act a to prevent and (or) to remove-ice-formation from such surfaces. The invention is particularly applicable to aerofoil and other surfaces on aircraft upon which ice is liable to form.

i It will be obvious that if the inhibition of ice formation is to be maintained de-icingliquid must be continuously supplied to the surface at a rate such as to maintain theloptimum film thickness in spite of theremoval of the liquid fromthe surface bythe action of air flow, ice formation and/or rain; Liquid distributing means are known whereby the deeicing liquid is caused to exude from one or more relatively narrow longitudinalsections of the surface to be-treated,- such means beingcharacterised by achannel orconduit from which a moreor less continuous lateral leakage path is provided through a textilestrip or by the mutual contact maintained between twotextile surfaces, or by the provision of a porous metallic mass formed by the sintering of By their nature such leakage paths or surfaces provide a variable and unpredictable resistance-.tothe flow of the liquid.

A serious disadvantage inherent in the use of such known liquid distributing means, is that it is difficult to ensure even distribution'over the whole of the-surface and it iseven more difficult to do so once the continuity of the surface is interrupted by the adhesion of ice onthe surface.

Further difiiculties arise due to the di-hedral angle of aircraft Wings andalso due tothe-verti cal disposition of the fin and rudder surfaces,

because, necessarily, one end of the liquid distributing means must be higherthan the other,

7 with the result-that when the distributing-means is not in use the contained-de-icing liquid flows slowly to the lower end and air enters through the porous surfaces at the top-end and-upper parts to displace the liquid as it flows downward.

necessary tofill up all-thespaces andchannels in the liquid distributingmeans-which are devoid of liquid beforeuniform exudation of theliquid can again take place.

= The ideal liquid distributing meansfor de-icing purposes is one in which theexudation, of the de-icing liquid takes place through apertures or pores which are, so closelyfispaced thatthe exudation is substantially continuous over the surface andis not localised. Sucha liquid distributing means, however, postulates the .use of a porous :mediumandsuch media, if constructed of sintered metal powder, are heavy and brittle, whilst if. constructed from fabric or other non-metallic substances are usually too variable in texture to provide the -requisite evenness of exudation of wane liquid. Further, by their nature the two classes of material referred to above owe their porosity to'the existence of fortuitous interstices,

which exudation of de icing liquid can be precisely: controlled in: accordance with known laws of liquid how and fromwhich, furthermore, the exudation rate over specified areas of the surface can be arrangedto be different from that of other areas.

According to thepresent invention, the liquiddistributing means is in the form of a flexible andresilientliquid-impervious strip (hereinafter called-a' de-icing strip) which is adapted to be attached to, or to form a part of, a member the surface ofwhich is to be kept free of ice and-which,'within its thickness, is provided-with a number of liquidfiow passages of predetermined size through which the flow of de-icing liquid :fedthereto under pressure will take place in accordance with the known laws of liquid flow, and

. some or all of which communicate with liquidexuding apertures in the outer or de-icing surface of the strip; the-.said apertures being closed except when forced open by the pressure of the de-icing liquid The arrangement is such that the resistance to flow of the whole system of liquid flow passages or'parts of the system is under control orpredetermined at the time of manufacture of the strip.

The de-icing strip may also be formed with one or more main de-icing'liquid supply channels which is, or are,-spaced from the outer or de- *icing surface of the strip but which, or each of which, is' put into communication with the de- -icing surface bythe liquid flow-passages and the apertures.

. the channel may be formed in. the aerofoil or iother,surfacetowwhichcthe strip is attached.

The main supply channeltmay communicate, through the liquid flow passages, with a number of liquid containing spaces or small well-like cavities formed in the mass of the material from whichthe de-icing strip is made, these cavities being connected tothe outer surface of the deicing strip by normally-closed slits or holes.

In a modified construction the liquid flow passages are connected at their outer ends with auxiliary liquid supply channels which are connected to the outer or de-icing surface of the strip by normally-closed, liquid-exuding fine slits or holes. v V

The de-icing strip may conveniently be moulded from plastics of the thermo-plastic type or of that type wherein polymerisation takes place after two or more reactive liquids have been mixed and poured into a mould. Alternatively,

it may be made from rubber, synthetic rubber or other similar mouldable flexible or resilient material. 1

The liquid flow passages which communicate with the main supply channel may be formed by embodying a number of fine wires or pins in the material during the course of manufacture of the de-icing strip, these wires or pins being withdrawnafter the materialhas set or hardened.

As an alternative, some or all of the liquid flow passages and (or) the auxiliary supply channels may be formed by soluble ligaments or material which are dissolved out of the strip after the latter has been moulded.

In one method of making the de-icing strip, the liquid flow passages are formed by fine wires or pins having heads which form the wall-like cavities, which latter are connected to the outer or ole-icing surface by liquid-exuding fine slits or holes which are cutor pierced in the strip after the latter has been moulded. If the strip includes a main supply channel the wires or pins may be fixed to a core which forms the channel during the moulding operation.

On other constructions, the liquid-exuding apertures are formed in members fixed in recesses which are formed in the de-icing strip during the moulding of the latter. In one method of making a de-icing strip of this, character each of the recesses is formed by a .core which forms the recess during the moulding operation and the liquid fiowpassages are formed by fine wires or pins or soluble ligaments or materials attached to the cores. 7 V V A number of constructional forms of the invention are shown, by way of example, on the accompanying drawings, whereon:

Figure 1 is a sectional ,view of a de-icing strip which comprises a tubular part, in which the main liquid supply channel is formed, and a 4 Figure 5 is a plan view of a fragment of a modified de-icing strip which comprises a tubular part in which the main liquid supply chansubsidiary liquid supply passages and the normally-closed fine slits are formed;

Figure 6 is a sectional view taken on the line 6--6 of Figure 5, looking in the direction of the arrows;

Figure '7 is a section through a curved de-icing strip in which a portion only of the main liquid supply channel is formed, the complementary portion being formed in the structure on which the strip is fitted;

I Figure 8 is asection through a modified curved de-icing strip formed with subsidiary liquid supply passages which communicate with a main liquid supply channel formed entirely in the structure on which the strip is fitted;

Figure 9 is a section through another modification of a curved de-icing strip;

Figure 10 is a plan view of a modified de-icing strip in which the subsidiary liquid supply passages communicate with subsidiary liquid supply channels which are connected to the outer or deicing surface of the strip by normally-closed fine slits Figure 11 is a sectional view taken on the line lI-H of Figure 10, looking in the direction of the arrows;

Figure 12 is a fragmentary sectional view of a de-icing strip showing one method of forming the fine, normally-closed slits and withdrawing the fine wires orpins which are used to form the subsidiary liquid supply passages and the well-like cavities in the strip;

Figure 13 is a sectional view of a de-icing strip mould showing an alternative method of providing communication with the de-icing surface of v the mould;

wing part in which the subsidiary liquid supply passages and the normally-closed slits are formed;

Figure 2 is a face view of the strip;

Figure 3 is an enlarged sectional view of a portion of the strip showing one of the well-like cavities and the normally-closed fine slit connecting the cavity to theouter surface of the strip and may be considered as taken substantially along the line 3-3 of Figure 2 looking in the direction of the arrows;

Figure 4 is an enlarged section of one of the subsidiary supply passages, the well-like cavity and the normally-closed fine slit connecting the passage to the outer surface of the strip and may be considered as being taken substantially along the line 4-4 of Figure 2 looking in the direction of the arrows;

Figures 15 to 17 are face views showing various types of liquid exuding aperture members; and

Figure 18 is a fragmentary sectional view showing a modified form of recess and aperture member.

Referring first to Figures 1 to 4:

In this constructional form of the invention, the de-icing strip comprises a substantially fiat plate or wing part I and an integral tubular part 2 which extends longitudinally along one edge of the wing part and projects rearwards from the rear face of the strip.

The strip is moulded from any of the materials referred to above, the mainsupply channel 3 in the tubular part 2 being formed by arranging a corelongitudinally in the mould. The inner ends of a large number of fine wires or pins 4, each having a large head 5 of bead form at its outer end, are inserted into the cor and project traversely therefrom toward the edge of the de-icing strip. The wires or pins 4 are so disposed that their heads 5 are close to, but do not contact, the top of the mould corresponding to the outer or de-icing face 6 of the strip. The plastic material is now poured into the mould and after it has been cured to ;the correct consistency it is removed therefrom and a fine slit I is cut in the outer face 6 of the strip opposite and down to the head 5 of each of the pins or wires 4. The slit is cut in a direction transverse to the main supply channels and the operation is performed by means of a fine knife so that no material is removed. Thus, as shown in Figure 3, the two valve forming lips la and lb formed on either side of the slit are normally closed leaving no aperture but they can, owing to'the resiliency of the material, as explained hereinafter, be pressed apart sufficiently to enable the head 5 of the wire or pin 4 to be gripped and the wire or pin withdrawn. As shown in Figure 4, the withdrawal of each wire or pin thus leaves a fine capillary-like passage 8 connecting the main supply channel 3 (formed by the subsequent withdrawal of the mould core) to a space or well-like cavity 8 for containing liquid and corresponding to the head 5 of the wire or pin 4 and a' normally closed liquidexuding duct formed by the slit 1 connecting the cavity to the outer face 6 of the strip.

.The wires or pins 4. may be so disposed that their heads 5 lie in one or more longitudinal rows or they may be arranged in any other relationship.

Further, the section of the wing part i of the de-icing strip may, as shown in dotted lines in Figure 1, be tapered, decreasing from a maximum at the tubular part 2, where it may, if desired, be thick enough to contain the whole of the tubular part, to a minimum at its opposite edge.

As explained above, owing to theresiliency of the material, the lips 1a and lb of each of the slits I normally close so as to leave no measurable aperture between them. De-ioing liquid is pumped under pressure into the main liquid supply channel 3 and thence through the subsidiary passages 8 to the well-like cavities or liquid containing spaces 9, whose lips la and (b on opposite sides of each slit 1 will be forcedopen by the liquid pressure, thus permitting the exudation of the liquid but they will be automatically closed if and when the internal pressure ceases, or becomes less than the external pressure. Thus, any tendency is counteracted for air to enter the cavities 9 and the passages supplying them, thus displacing the liquid.

, In a modified construction shown in Figures 5 and 6, the ole-icing strip is formed with its longitudinal tubular part ID placed centrally of the stri and with two flat or tapered wing parts I I and i2 extending laterally on opposite sides of the tubular part. The latter is again formed with a main liquid supply channel [3,.and the capillary-lilze subsidiary supply passages l4 extend laterally in both directions from the main supply channel. Each subsidiary supply passage supplies de-icing liquid to a well-like cavity [5 from which liquid. exudes on to the outer face of the strip between the lips of slits l6 formed inthe outer face of the strip as previously described.

In the modified construction shown in Figure 7, the main supply channel is not formed wholly in the material of the de-icing strip but is made up of a part l7 formed in the latter and a part 18 formed in the structure (for example an aircraft wing is) to which the strip is fitted.

In the construction shown in Figure 8 the main supply channel 2i! is formed Wholly in the "structure H to which the strip is fitted and is connected to the bottom of an arcuate recess 22 formed in the structure, and in which the deicing strip is accommodated, by a number of longitudinally spaced ducts 23. Inthis construceach duct 24 leading to'a we'll-like'cavity 25 connected to the outer face of the strip by afine slit 26 cut in that face.

5 terial has been poured into the mould. andcured For manufacturing reasons itmay usually be desirable to make the outer or de-icing surface of the strip flat. It will be understood, however, that the wing parts or other aerofoil surfaces to which the de-icing strips may be attached are usually curved and to suit the profiles of u structures to which the strips are fitted-the latter, owing to their resiliency, may be ben't. On the other hand it may be desirable to mould the strip into a pre-curved section such that it can be applied without distortion. v Examples of curved de-icing-s'trips are shown in Figures 8 and 9, while Figure 7 shows a strip with a curved outer surface and a flat inner surface. In any case, as shown in Figures 7 to 9, it may be convenient to provide a longitudinal recess orhousing in the front surface of the structure to serve as a seat for the de-icing strip.

Instead of using separate headed wires or pins as described above to form the said capillarylike supply passages, each terminating in a separate well-like cavity in thernaterial of the deicing strip, the outer ends of a number of longitudinally-spaced wires or pins 28 may be attached to rods 29 as shown in Figure 10. In this way, when the strip is mouldedit will be formed with a number of sets of capillary supply passages each set providing communication between the main supply channel to and one or more longitudinal auxiliary channels 3i of smaller size. A number of longitudinally-spaced transverse slits 2-32, as described'above, would then be cut from the outer surface of the strip down to the auxiliary longitudinal channel or cliannels 3i.

Since in this construction the wires forming the capillary supply passages are not fitted with heads which have to be withdrawn through the slits 32, the latter may be replaced by fine holes. These holes are pierced, not drilled or moulded, so that no material is removed and hence normally they have no measurable diameter. Therefore, as in the case of the previouslydescribed slits, the holes normally are closed and are only forced open by the pressure of the de-icing liquid pumped through them.

Furti in this construction, since it is practically impossible to remove the wires or pins forming the capillary passages by. mechanical means as described in connection with the constructions shown in Figures 1 to 9, they may be made of soluble ligaments which subsequently would be dissolved out by means of a solvent.

It will also be appreciated that this method of construction could equally be applied to the larger passages such as 3! (Figures, 10 and 11) and 3 (Figure l) and to the well-like cavities shown in Figures 1 to 9, the cores forming these passages and cavities also being made of soluble material.

Further, it will be appreciated that, if this method of removing the ligaments or cores were adopted in the constructions shown in. Figures 1 to 9 then the liquid-exuding slits usedtherein could be replaced by pierced holes.

The de-icing strips as described herein, may be attached to the members to be de-iced by adhesion or by mechanical means. They may be fitted in recesses as shown at 33 in Figure 7, at 22 in Figure 8 and at 39 in Figure 9, so that their outer surfaces will be flush with the outer surfaces of the said members.

The cutting of the liquid-exuding slits may conveniently be performed in a machine as indicated in Figure 1 After. the mouldable mait is placed in the machine where the fine slits 33 are cut by means of a razor blade-like tool 34a which has a reciprocating vertical movement. After the slits have been out the pins 35 will be removed by bending the strip backwards as shown at 36, enabling the heads 37 to be gripped by'means of a pair of forceps inserted into the slits and withdrawn as shown in dotted lines. It will be appreciated that by substituting a needle for the blade 34, holes of the type described above may also be pierced in the strips.

It will be clear from the above that a de-icing strip having main and subsidiary passages made in accordance with this invention has a controllable porosity or resistance to flow and does not owe its porosity to fortuitous interstices as referred to above.

It will also be obvious that the said passages can be formed by means other than by using cores, pins or wires inserted in the mould and mechanically removed, or by the use of some form of ligament or soluble core which is subsequently dissolved by means of a solvent.

Other means could be used for producing the passages and/or slits or holes. For example, in a further construction the de-icing strip is made in a split mould having a base 40 and a cover 4|, as shown in Figure 13. In the cover part M which forms the face of the strip are formed a number of holes in which are mounted a number of studs each having a parallel slidable shank 42, a shoulder 43 and a short head 44. A fine lateral hole 45 into which a wire 455, adapted to form a capillary passage in the de-icing strip, can be inserted is formed in the head 45.

After the plastic material has been poured into the mould and cured to the right consistency the cover 4| is lifted, leaving the studs 42 with their shoulders 43 and heads lid embedded in the strip, which with the studs is then removed from the mould base 40.

The strip is now stretched sideways sufficiently to disengage the end of the wire 46 from the hole 45 in the head part so that the studs can be removed leaving recesses Ill as shown in Figure 14. After all the studs have been removed the strip is permitted to return to its original form in which the wires 46 again protrude into the recesses left by the head parts 44. The wires can then be gripped by forceps and withdrawn.

A disc of one of the forms shown in Figures 15 to 17 is placed in each of the recesses 41 formed by the shoulders 43. Disc 50 may be formed as shown with a single slit while disc 52 has a star-shaped slit 53 having three or more arms and disc 54 has one or more pierced holes 55.

In a modified form the shoulder 43 may be made tapered so as to produce an undercut-type of recess as shown at 56 in Figure 18, the material being sufliciently resilient to permit of the extraction of the tapered shoulder and the entry of the disc which is similarly formed.

In any construction the disc can be secured in position either by means of an adhesive or by welding i. e., by raising the local temperature sufficiently high to soften the mating surfaces and secure adhesion.

It will also be appreciated that in this construction the discs may be made of a different grade of plastic from that of the strip so that in this way a grade more suitable for slitting or piercing may be chosen.

I claim:

' 1. A de-icing strip comprising a fiexi'ble, resilient, liquid impervious member having an outer surface adapted to form part of a surface to be kept free of ice, a plurality of liquid flow control passages of predetermined size extending wholly within said member and having inner and outer ends, the inner ends of said passages being adapted to be connected to a main liquid supply channel supplied with liquid under pressure, a small well-like cavity formed within said member at the outer end of each of said liquid iiow control passages, and valve means comprising a pluralityof normally closed passageways formed by slits extending between the outer surface of said member and said cavities and which are adapted to be forced open only by the pressure of the de-icing liquid.

2. A de-icing strip comprising a flexible, resilient, liquid impervious member secured to a structure having an outer surface, saidstrip having an outer surface continuous with said surface of said structure and said surfaces to be kept free of ice, a plurality of liquid flow control passages of predetermined size extending wholly within said member, said member and said structure having mating parts shaped to form at least one main liquid supply channel spaced from said outer surface and communicating with said liquid flow control passages, said liquid supply channel being adapted to be supplied with liquid under pressure, a small well-like cavity formed at the outer end of each of said liquid flow control passages, and valve means comprising aplurality of normally closed passageways formed by slits extending between the outer surface of said member and said cavities and which are adapted to be forced open only by the pressure of the deicing liquid.

3. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface forming part of a surface to be kept free of ice, a plurality of liquid flow control passages of predetermined size extending wholly within said member and having inner and outer ends and adapted to be supplied with de-icing liquid under pressure, a small well-like cavity formed within said member at the outer end of each of said liquid flow control passages, and valve means comprising a plurality of normally closed passageways formed by slits extending between the outer surface of said member and said cavities and adapted to be forced open only by the pressure of the de-icing liquid.

4. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface forming part of a surface to be kept free of ice, a plurality of liquid fiow control passages of predetermined size extending wholly within said member and having inner and outer ends, at least one main liquid supply channel formed in said strip and spaced from said outer surface and communicating with the inner ends of said liquid flow control passages, said liquid supply channel being adapted to be supplied with liquid under pressure, a small well-like cavity formed within said member at the outer end of each of said liquid flow control passages, and valve means comprising a plurality of normally closed 'passageways formed by slits extending between the outer surface of said member and said cavities and adapted to be forced open only by the pressure of the de-icing liquid.

5. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface forming part of a surface to be kept free of ice, said member including a tubular part, a main liquid supply channel formed in said tubular. part and adapted towbe supplied with.

a plurality of liquid vflowucontrolpassages of prea determined size extending withinsaid wing part I and having innerand outer ends. and having theirinner ends connected -to saidwmain i liquid.

supply channel, a plurality .of liquid. containing. spacesformed within saidmember, each of said...

spaces communicating wwithuthe outer end of at least one of said liquid flow control passages, and valve means comprising a plurality of normal ly closed passageways formed by slits extending between said outer surface of said member and said spaces and which are adapted to be forced open only by the pressure of the de-icing liquid.

6. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface forming part of a surface to be kept free of ice, said member including a tubular part, a main liquid supply channel formed in said tubular part and adapted to be supplied with de-icing fluid under pressure, two wing parts extending laterally from and on opposite sides of said tu bular part, a plurality of liquid flow passages of predetermined size extending within said wing parts and having inner and outer ends and having their inner ends connected to said main liquid supply channel, a small well-like cavity formed within said member at the outer end of each of said liquid flow control passages, and valve means comprising a plurality of normally closed passageways formed by pierced slits extending between said outer surface of said member and said cavities and adapted to be forced open only by the pressure of the de-icing liquid.

7. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface forming part of a surface to be kept free of ice, said member including a tubular part, a main liquid supply channel formed in said tubular part and adapted to be supplied with deicing liquid under pressure, two Wing parts extending laterally from and on opposite sides of said tubular part, a plurality of liquid flow control passages of predetermined size extending within said wing parts and having inner and outer ends and having their inner ends connected to said main liquid supply channel, a plurality of auxiliary channels formed in said Wing parts, each of said auxiliary channels being connected to the outer end of at least one of said liquid flow control passages, and valve means comprising a plurality of normally closed passageways formed by pierced slits extending between said outer surface of said member and said auxiliary channels and adapted to be forced open only by the pressure of the de-icing liquid.

8. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface forming part of a surface to be kept free of ice, a plurality of liquid flow control passages of predetermined size extending wholly within said member and having inner and outer ends, at least one main liquid supply channel formed in said strip and connected to the inner ends of said liquid flow control passages, said liquid supply channel being adapted to be supplied with de-icing liquid under pressure, a plurality of auxiliary channels formed in said member, each of said auxiliary channels being connected to the outer end of at least one of said liquid flow control passages, and valve means comprising a plurality of normally closed passageways formed by pierced slits extending be- 10., I, tweensaid outer surface of said memberrandsaid auxiliary channels and adaptedto be forced open only by the pressure of the de-icing liquid.

9. A de-icing strip comprising a flexible, resilient, liquid impervious memberhaving a tubular part forming a main liquid: supply channel adapted to be supplied with de-icing liquid under pressure, at least one wing part extending laterally from said 'tubular part, a plurality of liquid flow control passages extending wholly within said Wing partand having'inner and outer ends and having their inner ends connected to said main liquid supply channel, a small welllike cavity formed within said wing part at the outer end of each of said liquid flow control passages, and valve means comprisin a plurality of normally closed passageways formed by slits extending between the outer surface of said member and said cavities and which are adapted to be forced open only by the pressure of the deicing liquid.

10. A de-icing strip comprising a flexible, resilient, liquid impervious member secured to a structure having an outer surface to be kept free of ice, said member and said structure having mating faces shaped to form a main liquid supply channel adapted to be supplied with de-icing liquid under pressure, said member having two wing parts extending laterally from and on op posite sides of said supply channel, a plurality of liquid flow control passages extending wtihin said wing parts and having inner and outer ends and having their inner ends connected to said main liquid supply channel, a plurality of liquid containin spaces formed within said wing parts, each of said spaces communicating with the outer end of at least one of said liquid flow controlling passages, and valve means comprising a plurality of normally closed passageways formed by slits extending between the outer surface of said memher and said spaces and which are adapted to be forced open only by the pressure of the de-icing liquid.

11. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface adapted to form part of a surface to be kept free of ice, a plurality of liquid flow control passages of predetermined size extending Wholly within said member and having inner and outer ends, the inner ends of said passages be ing adapted to be connected to a main liquid supply channel supplied with liquid under pressure, at least one liquid containing space formed within said member and in communication with the outer end of at least one of said liquid flow control passages, and valve means comprising at least one normally closed passageway formed by a slit extending between the outer surface of said member and said liquid containing space and adapted to be forced open only by the pressure of the liquid.

12. A de-icing strip comprising a flexible, resilient, liquid impervious member having an outer surface adapted to form part of a surface to be kept free of ice, a plurality of liquid flow control passages of predetermined size extending wholly within said member and having inner and outer ends, the inner ends of said passages being adapted to be connected to a main liquid supply channel supplied with liquid under pressure, an opening formed in said member at the outer end of each of said liquid flow control passages, and a valve disc closing said opening and defining therewith a small liquid containing space at the outer end of each of said liquid 11 flow control passages, said valve disc providing a normally closed passageway formed by a pierced opening in said disc extending between the outer surface of said member and said liquid containing space and adapted to be forced open only by the pressure of the liquid.

References Cited in the file of this patent UNITED STATES PATENTS Number Number Name Date Duden Feb. 27, 1940 Booharin Oct. 15, 1940 Bulloch July 22, 1941 Robinson Oct. 7, 1941 Sidne11 June 9, 1942 Morse et a1 Nov. 9, 1943 Milano Oct. 16, 1945 Campbell Apr. 6, 1948 Gregg Jan. 30, 1951

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