US2149388A - Controllable pitch propeller - Google Patents

Description

March 7, 1939. F. wv CALDWELL I 2,149,388

CONTROLLABLE P I TCH PROPELLER Filed Oct. 1, 1935 Patented Mar. 7,- 1939 UNITED STATES PATENT OFFICE Frank W. Caldwell, Hartford, Conn., assignor to United Aircraft Corporation, East Hartford, Com, a corporation of Delaware Application October 1, 1935, Serial No. 43,006 3 Claims. (Cl. 170-163) This invention relates to improvements in controllable pitch propellers and has particular reference to improvements in means for temporarily restraining the controlling mechanism of a controllable pitch aeronautical propeller against changing the pitch angle of the propeller.

An object of the invention lies in the provision of a light, simple and,efiective means for positively restraining the pitch controlling .mecham nism from changing the pitch angle of the propeller during the time the restraining mechanism is operative. l I

A further object resides in the provision of an electrically operated valve for restraining the 15 pitch controlling mechanism of a controllable pitch propeller from changing the pitch angle of the propeller during the time the electric valve actuating mechanism is operative.

, Other objects and advantages will be apparent m as the description proceeds.

In the accompanying drawing in which like reference numerals refer to similar parts I throughout there is illustrated, a suitable mechanical embodiment of what is now considered ,5 to be the preferred form of the invention. The

drawing, however, is for the purpose of illustration only and is not to be taken as limiting the invention, the scope of which isto be measured entirely by the scope of the appended claims.

a In the drawing,. the single figure is a vertical elevational view of a controllable pitch propeller showing the application thereto of the device of the invention, certain portions of the propeller mechanism being broken away to better illustrate as the construction thereof, and the device of the invention being illustrated in section.

For a" more complete disclosure of a suitable propeller mechanism with which the device of the invention may be associated, reference may 40 be had to my co-pending application Serial No. 656,533, filed February 13, 1933, for Propellers.

Referring tothe drawing in detail the numeral Ill generally indicates the front or nose plate of a suitable power plant such as a radial air cooled 6 internal combustion engine. This front plate is provided with a bearing receiving aperture I! through which projects a power shaft l4 upon the projecting end of which is mounted the controllable pitch propeller generally indicated at l l3. This propeller has a plurality of hollow blades as indicated at It and 20, each blade being provided in the hollow base or root end thereof with a cylindrical flanged sleeve as indicated at 32. These sleeves are rotatably mounted upon I radially projecting arms 24 and 23 formed upon a spider having a central cylindrical portion 23 non-rotatably fixed upon the projecting end of the shaft l4. The blades are retained upon the, spider arms 24 and 26 against the action .of centrifugal force by means of thrust bearings as indicated at 30 which bear against the inturned ends 32 of a split barrel member 34. Arms, as indicated at 36 and 38, are non-rotatably secured to the flanged base portions of the sleeves 22'of the propeller blades l8 and 20 respectively and 10 project forwardly from the propeller blades substantially parallel to the axis of the shaft l4. Each ofthe' arms 36 and 38 is provided with a cam slot 40 extending therethrough for a purpose to be presently described, and each arm carries upon the outer or free end thereof, a counterweight 42. These counterweights are so disposed with relation to the axes of the blades l8 and and .the axis of the shaft l4 about which the propeller rotates that, upon rotation of the pro- 20 peller, the counterweights under the influence of centrifugal force tend to rotate the blades l8 and 20 in a direction to increase the pitch angle of the propeller blades.

A hollow piston 44 is secured upon the forward end of the cylindrical spider portion 28 so that its center line is coextensive with the projection of the axis of the shaft l4 and a cylinder 46 is mounted for reciprocation upon the piston 44' and is provided upon diametrically opposite sides 30 thereof with radially extending arms 48 which carry pins 50 which extend into the cam slots provided in the counterweight arms 36 and 38 to operatively connect the reciprocable cylinder 46 with the counterweight arms so that an out-' 5 ward movement of the cylinder 46 with respect to the piston 44 will exert a force upon the counterweight. arms opposing the centifugal force of the counterweights 42 to rotate 'the propeller blades l8 and 20 toward a low pitch position. Hydraulic 40 fluid from a suitable source such as the lubricating pump of the engine, or-an'auxiliary pressure pump, is supplied to the space between the for-' ward end of the piston 44 and the end wall 50 of the cylinder 46, through an axial bore in the 45 shaft l4 and through the interior of the hollow piston 44. The engine is provided with a carburetor not illustrated, which carburetor is adjustable in the usual manner to regulating the relative propor- ,sure corresponding to the various altitudes at which the engine is operated. The mixture controlling mechanism of the carburetor is adjusted by a hand lever 64 mounted in some location convenient to the operator of the vehicle upon which the engine and propeller are mounted and connected with the carburetor by a suitable link mechanism.

The customary method of adjusting the mixture control of an internal combustion engine such as is ordinarily used for the propulsion of aircraft consists in general of maintaining the engine throttle in a fixed position and then adjustlng the mixture control lever until the revolutions per minute of the engine reach a maximum as indicated on a tachometer visible to the operator. In some instances after the best mixture ratio has been obtained, the mixture control lever may be moved slightly toward the lean or rich positions to either provide a lean mixture to give maximum fuel economy or a slightly rich mixture to prevent overheating of the engine cylinders. It is obvious that this mixture regulating operation must be carried out with a constant pitch angle setting'of the propeller blades as any change in the blade angle will affect the revolutions per minute of the engine so that the operator would be unable to tell at what mixture ratio the engine revolutions were at the maximum rate per. minute. As the controllable pitch propeller automatically adapts its blade angle to the power output of the engine to maintain constant the number of engine revohead of the valve member generally indicated.

lutions per minute, in order to permit accurate mixture ratio adjustment some means must be provided to maintain the propeller blade angle constant during the mixture adjusting operation. In the present invention this means takes the form of a suitable solenoid actuated valve generally indicated at 58, disposed within the hole .low piston 44 in a position to control the flow of hydraulic fluid Ito and from the space between the piston and the end wall.52 of the cylinder 46. When the cylinder 46 is thus retained in fixed position relative to the piston 44, the arms 36 and 38 are restrained against movement and the propeller blades I8 and 28 are held at a fixed blade angle.

The valve 58 comprises a hollow cup shaped member 68 open at its forward end and provided at its closed rearward end with a cylindrical reduced portion 62 which forms a casing for the at 64. 'The casing member 68 is provided with an out-turned flange 66 which overlies a portion of the forward end of the piston 44 to provide a bearing surface for securing the casing to the piston. Within the casing 68 there is a hollow cylindrical solenoid casing 68 enclosing a solenoid I8; The solenoid'casing 68 has an outer diameter less than the inner diameter of the casing 68 and is disposedwithin the casing 68 so that its exterior surface is annularly spaced from the interior surface of the casing 68 as indicated at 12 to provide a passage for hydraulic fluid between the solenoid casing and the cup shaped casing 68. The solenoid casing 68 is provided at its rearward end with :an annular extension within which is formed a beveled valve seat 14 which cooperates with a similar valve seat 16 formed on the enlarged head portion of the valve 64. A plurality of ports 18 extend through the reduced portion 62 of the casing 68 and the extension on the solenoid casing to the space between the valve seats I4 and I6, and a plurality of ports 88 lead from this space into the space between the solenoid casing and the cup shaped casing 68 to provide a passage through the valve mechanism for bydraulic fluid when the valve is open. A coiled compression spring 82 is disposed between-an annular extension 84 upon the rear end of the valve head and the rear end of the annular extension formed on the solenoid casing 68 to resiliently urge the valve toward the open position illustrated in the drawing. The valve is provided with an integral cylindrical armature 86 which projects into a cylindrical bore provided in the solenoid casing 68 so that when the solenoid I8 is energized the armature will be moved to the left as viewed in the figure to bring the valve seats 14 and I6 into contact with each other and thus close the valve. A plate member 88 overlies the forward end of the solenoid casing 68 and the flange 66 on the casing 68, and is provided at its center with a plug 98 extending into the armature bore in the solenoid casing to increase the magnetic flux within the bore. The flange 68 and the plate are apertured as indicated at 89 to provide a passage for hydraulic fluid from thespace 12 to the space between the piston and the cylinder. The plug 98 is provided with an axial bore or aperture 82 leading into the space between the inner end of the plug and the adjacent end of the armature 86 to relieve -any pressure that might build up in this space and tend to retard movements of the armature. A plurality of pressure release bores 94 are also provided in the valve head to relieve any pressure that might accumulate between the valve head and the end wall 96 of the valve casing 62.

- The valve is maintained in fixed relation to the piston 44 by means of a plurality of insulated screws as indicated at 88, and the solenoid leads I88 are connected to the ends of one pair of these screws at the ends thereof which project into the space between the piston 44 and the cylinder 46. Electrical leads I82 are connected to the ends of these screws lying within the piston 44 and are led to respective contact rings I84 and I86 mounted in a ring 188 of insulating material secured upon the rear end of the cylindrical portion 28 of the propeller spider. The rings I86 and I88 are enclosed by an annular casing II8 rigidly secured to the front plate I8 of the engine surrounding the aperture through which the shaft I4 projects. A pair of contact brushes H2 and H4 are mounted in a block II6 of insulating material carried by the casing H8 and are spring pressed into contact with the'rings I84 and I86 respectively in the usual manner. A pair of electrical conductors H8 and I28 extend from the brushes H2 and H4 respectively to the opposite sides of a switch mounted upon the mixture control handle 54-, one of the conduits leading through a suitable source of electrical energy such asthe battery I21. This switch comprises a contact button I22 secured to the knob of the mixture control handle and a leaf spring I24 provided with a contact point I26 secured to the stem portion of the handle and so positioned that the contact point I26 is in alignment with the contact button I22 but is normally spaced therefrom. The switch is ordinarily open, the solenoid I8 is deenergized and the valve 64 is urged to its open position by the spring 82, thus permitting automatic regulation of the blade angle by the ifsual speed responsive device through which the hydraulic fluid is fed to the propeller controlling mechanism. When the operator grasps the mixture control lever 54 he incidentally bends the leaf spring I24 so that the switch contacts I22 and ii. are closed. Thus, during the time that the mixture control is being adjusted the switcli is maintained closed, the solenoid 10 is energized and the valve 64 is closed so that the propeller controlling mechanism is rendered inoperative to change the blade angle of the propeller during the mixture regulating operation. When the operator releases the lever 54 the resiliency of I the leaf spring I24 automatically opens the switch and restores the. propeller controlling mechanism to the'regulation oi the speed responsive mechscribed but that such changes in the size, shape and arrangement of parts may be resorted to as come within the scope of the subjoined claims.

Having now described the invention so that others skilled in the. art may clearly understand the same, what it is desired to secure by Letters Patent is as follows:

What it is claimed is:

1. In a controllable pitch propeller, a rotatable hub, a plurality of propeller blades mounted on said hub for rotational adjustment about their respective axes, centrifugal means. for adjusting the pitch angle of said blades in one direction, hydraulic means carried by said hub for adjusting the pitch angle of said blades in the opposite direction, means for supplying fluid under pressure to said hydraulic means irom a fluid pressure source remote from said propeller, a solenoid actuated valve carried by said hub operative to interrupt the flow 0t fluid to and from said hydraulic said hub to slide on said rings, a source oi electrical energy, a manually operable switch, and

1 electrical connections between said solenoid and said rings and betweensaid brushes said source 01' electrical energy and said switch.

2. In a controllable pitch propeller, a rotatable 'hub, a plurality of propeller blades mounted on said hub for rotational adjustment about their respective axes, centrifugal means for adjusting the pitch angle oi! said propeller blades in one direction, hydraulic means comprising a piston fixed on said hub and a cylinder slidable on said piston operatively connected with said blades for adjusting the pitch angle of said blades in the opposite direction, a passage for fluid through said piston, a valve ands solenoid for actuating the same located in said piston to interrupt the flow of fluid through said passage, and remote control means for energizing said solenoid.

3. In a controllable pitch propeller, a rotatable hub, a plurality of propeller blades mounted on said hub for rotational adjustment about their respective axes, centrifugal means for increasing the pitch angle of said blades, hydraulic means for decreasing the pitch angle of said blades said hydraulic means comprising a piston fixed on said hub and a cylinder slidable on said piston and operatively connected with said means, a solenoid actuated valve in said piston for controlling the movement 01' said cylinder by interrupting the flow oi fluid to and from the space between said cylinder and said piston, and remote control means for energizing said solenoid.

centrifugal mam: w. CALDWELL.

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