1934. J..D. PEACE, JR 1,971,534

PITOT STATIC TUBE Filed Aug. 11, 1932 IN V EN TOR. JO/l/V D. PEACE, Jr.

ymwma A TTORNEX Patented Aug. 28, 1934 Bendix Aviation Corporation, South Bend, 1nd,, a poration of Delaware 1 Application August '11, 1932, Serial No. 628,429

I teams. (01. is ie'nf The present invention -relates-toPitot-static tubes of the type adapted for use on aircraft to determine the air speed of the latter and more particularly to means for heating said tubes.

One of the objects of the invention is to provide a novel Pitot-static tube embodying avconstruction of simple design which is easy to assemble and disassemble, thereby facilitating rem placement-of parts, and a. construction which renders the tube particularly suitable and efficient for use in obtaining the air speed of anair-- craft. v

Another object is to provide a Pitot-static tube embodying novel means for heating the same whereby the forming of ice or the packing of snow at ,the entrance of the tube or within the chamber which communicates with the moving air may be obviated so that proper function- 2 ing of the tube may be assured when fiying'during cold, weather or in inclement weather.

Another-object is to provide in a Pitot static tube having two chambers, one of which is adapted to receive the impact of an air stream for transmitting the velocity pressure and. the

other of which is open to the surrounding at-- mospherebut unaffected by the air stream for transmitting the static pressures, a heating coil for one of said chambers, and novel means whereby said coil may be automatically connected in an electric circuit upon the placing and securing of said coil in said chamber, therebyeliminating the necessity of making manual connections of wires to terminals or binding posts. v e

A further object of the invention is to provide a novel heating coil for-Pitot-static tubes whereby said coil may be readily removed from the tube and replaced by another without re-' quiring disconnecting and connecting of wires, and which is automatically placed in an electric circuit by merely positioning the'coil within the chamber of the tube with which it is associated. The above and otherobjects and'advantages and novel features of the construction and combination of .parts of thedevice embodying the present invention will appear more fully hereinafter from a consideration of ithe detailed description which follows, when taken in conone embodiment of the invention is illustrated. It is to beexpressly understoodhowever, that the drawing is for the purpose of illustration and description only and is not designed as a definition of the limits of the invention. reference fner of supporting the same for operation;

nection with the accompanying drawing whereinbeing had for this purpose to the appended claims. 1

In the drawing wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a longitudinal section of one form of novel Pitot-static tube embodying the present invention; I

Fig. 2 is a side'view thereof showing the'man- Fig. 3 is an end view as viewed from the left of Fig. 2; and

Fig. 4 is a detail view showing the manner in which the novel heating coil of the tube is constructed and assembled.

The Pitot-static tube embodying the present invention is of the type disclosed in a copending application of Charles H. Colvin, Serial No. 261,466 filed March 14, 1928, and comprises, in the form shown herein, three sections 5, 6 and 7. The section'5 is in the form of a metal tube or casing having one end thereof curved inwardly as indicated at 8 and the other end threaded internally as indicated'at 9' for securing the tube to the middle section 6. The other outer sec- 0 tion 7 has one end thereof closed in any suitable manner as, for example, by means ofa streamlined cap 10 and is also secured to the middle section 6, as by means of a pressed fit. The section 5 is provided with an opening 11 and constitutes the velocity pressure end of the Pitotstatic tube for transmitting pressures due to velocity head, and the other section 7 is provided with a plurality of apertures 12 in the walls thereof and is utilized for transmitting pressures due to static or pressure head. coinciding with the opening 11 at the end of the tube 5 and extending within thelatter is a tube 13 having its inner end closedby a plug 14 in which are provided openings 15 and 16 and to which is secured or formed integral therewith a bafiie plate 17, the latter serving to prevent foreign materials from entering the tube and being passed to the air-speed indicators.

Supporting member 6 is provided with a pair of passages 18 and 19 which connectwith the sections 5 and 7 respectively. A'pair of tubes 20 and 21 extend transversely of and into the supporting member 6 and connect with the passages 18 and 19, respectively, by means of cut away portions 22 and 23 provided at their ends for transmitting the pressures produced within the tubes 5 and '7 to a remote point, as for example to an instrument panel on an aircraft Where they may be connected to an air speed is mounted is flying at high altitudes where very low temperatures are prevalent, or when flying in inclement weather, ice tends to form or snow tends to pack at the opening 11 of the tube, thereby clogging said opening or completely closing it andrendering the tube inoperative. It is, therefore, desirable to prevent such ice formations, and for this purpose means are provided whereby the velocity tube 5 may be heated, thus preventing ice and snow from adhering to the tube. In the form shown, such means comprise a heating coil 24 which may be connected in an electrical circuit by means of a singlewire-ground-return system including a sourceof electric current (not shown) for heating said coil. I

It is also desirable that the coil 24 be readily and easily inserted into and/or removed from the tube 5, thereby facilitating the replacement thereof. To this end a novel construction is employed embodying novel means whereby the coil is automatically interposed into the electrical circuit upon the placing thereof within the tube 5 and upon securing of the latter to the supportingmember 6. This may be accomplished as shown in the detailed view in Fig. 4. In order to effect the automatic interposition of the coil into the circuit, said coil is provided at either end thereof with flanged collars 25 and 26, respectively, to which are adapted to be soldered ends 2'7 and 28 of the heating coil 24. and the collars are then placed over the ends of the coil to provide contact surfaces, one of which (collar 25) contacts with the interior surface of the tube 5, as shown in Fig. 1, and the other of which is adapted to contact with a resilient conducting ring 29 imbedded in an insulating ring 30, said ring 29 having soldered thereto end 31 of a suitable insulated cable 32. The-cable may be connected to a source of current (not shown) such as a battery, for example, having one terminal thereof grounded. The return circuit of the coil is then provided through the ground formed by any suitable metal structure with which the tube is associated so that the collar 25, by virtue of its contact with the metal tube 5, constitutes the grounded side of the coil 24.. The conductor 32 is led out of the tube through a recess 33 provided in the upper portion of the supporting section 6 and through a tube 34 similar to the tubes 20 and 21, extending transversely of. and partly into said member 6.

The three tubes 20,21 and 34 are held together by means of suitable clamps 35 and 36 and are bent in such a manner that the Pitot-static tube projects from its support (not shown) to which the'three tubes may be clamped, as by means of brackets 3'7 and 38.

It will be apparent from the foregoing that when it is desired toremove the heating coil 24 for inspection or replacement thereof in case of its being burned out, all that is necessary to do is to unscrew the tube 5 from the supporting memberjfi' and remove the coil from said tube. As" soon as the tube 5 is unscrewed from the section ',6,the heating coil, by virtue of the disengagement of the collar 26 from the ring 29, is immediately disconnected from its electrical circuit without necessitating the disconnection of any wires. .A new coil may then be placed within the tube 5 so that the collar 25 at one thereof contacts with the inner wall of said tube and the latter may then be secured to the supporting member 6 by means of the threads 9, whereupon the collar 26 at the other end of the coil presses firmly against the resilient ring 29 which is permanently connected to the insulated conductor 32.

There is thus provided a Pitot-static tube embodying a novel structure of a heating unit whereby the latter may be easily and quickly assembled and/or replaced without requiring connecting and disconnecting of wires from terminals and whereby the coil is automatically interposed in the electrical circuit which is adapted to energize it, by simply placing the coil within the nosepiece of the tube and securing said nosepiece to the tube.

- Although only one embodiment of the invention has been illustrated and described, various changes and modifications in the form and relative arrangement of parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a Pitot-static tube unit having a metal tube section, one end of which is open to receive the impact of an air stream, a second tube section, the sides of which have apertures connecting it to the surrounding atmosphere, a member interposed between said tube sections for supporting the same, said member having two passages, one of which connects to the first tube section and the other of which connects to the second tube section, the combination of an electrical heating coil in said first tube section and having metal collars at its ends to which the opposite ends of the winding of the coil are electrically connected. thereby providing contact surfaces for said coil, one of said surfaces being in contact with the inner surface of said first tube section, and means including a lead wire adapted to contact with the other surface of the coil when said tube section is secured to the supporting member, said lastmentioned means being insulated from said tube section. I

2. In a Pitot-static tube unit comprising a removable metal tube section having one end open to receive the impact of an air stream, a

second tube section which is closed but which is provided with one or more apertures for establishing communication with the surrounding atmosphere, and means for connecting said tube sections to a difierential pressure-responsive de= vice, the combination of an electrical heating coil in said first tube section and having metal collars at its ends to which the opposite ends of the coil are electrically connected, thereby providing electrical contact surfaces for said coil, one of said surfaces being in contact with the inner surface of said first tube section when the latter is placed in position, and means including a lead wire adapted to contact with the other surface of the coil when the latter is held in the unit by the first tube section, said last-mentioned means be-= ing insulated from said tube section.

3. In a Pitot-static tube comprising a removable metal tube section having one end open to receive the impact of an air stream, a second tube section which is closed but which is provided with one or more apertures for establishing communication with the surrounding atmosphere, an annular member interposed between said tube sections and to which the latter are secured, and

means for connecting said tube sections to a differential pressure-responsive device, the combination of an electrical heating coil in said first tube section and having metal collars at its ends to which the opposite ends of the coil are electrically connected, thereby providing electrical contact surfaces for said coil, one of said surfaces being in contact with the inner surface of said first tube section when the latter is secured to the intermediate member, and means including a lead wire adapted to contact with the other surface of the coil, said last-mentioned means being insulated from said tube section.

4. In a Pitot-static tube having a removable metallic tubular portion constituting an electrical ground return, the combination of an electrical heating coil within said metallic tubular portion, and means for automatically connecting said coil in an electrical circuit upon securing of the coil within said metallic tubular portion and to said tube, said means comprising an insulated ring concentrically positioned within the metallic portion of said tube, a resilient conducting ring within said insulated ring, a lead wire secured to said conducting ring and providing an external connection from one end of said coil, and a pair of conducting collars carried by the ends of the coil and electrically connected to the respective ends of the winding thereof, one of said collars being adapted to bear against the resilient conducting ring upon securing of the coil within said metallic tubular portion and to said tube, and the other collar being adapted to bear against the inner surface'of the metallic portion of the tube for grounding the other end of the coil.

JOHN D. PEACE, JR.