US2302042A

US2302042A - Propeller control mechanism

Info

Publication number: US2302042A
Application number: US180592A
Authority: US
Inventors: Martin Erle
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1937-12-18
Filing date: 1937-12-18
Publication date: 1942-11-17
Anticipated expiration: 1959-11-17

Description

NOV. 17, 1942. -rm 2,302,042

PROPELLER CONTROL MECHANISM Filed Dec. 18, 1937 2 Sheets-Sheet 1 INVENTOR. E119 Marlin A TTORNEY Nov. 17, 1942. I E, MAR' N I 2,302,042

PROPELLER CONTROL MECHANISM Filed Dec; 18, 1937' 1 2 Sheets-Sheet 2 My a INVENTOR. Erl Marlin A TTORNE Y Patented Nov. 1 7, 1942 PROPELLER CONTROL IMECHANISM Eric Martin, West Hartford, Conn, assignor to United Aircraft Corporation, East Hartford, Conn.,' a corporation of Delaware Application December 18,1937, Serial No. 180,592 7 Claims. (01. I'm-135.6)

This invention relates to improvements in control means for controllable pitch propellers and has for an object the provision of an improved control means for regulating the propeller speed and for maintaining two or more pfopellers in synchronism with each other automatically while making provision for a manual control whenever desired.

Other objects and advantages will be more particularly pointed out hereinafter or will become apparent as the description proceeds.

In the accompanying drawings in which like reference numerals are used to designate similar parts throughout, there is schematically illustrated a combination of elements arranged according to what is now considered'to be the preferred form 01' the invention, and a somewhat modified arrangement of similar elements. The

drawings. however, are for the purpose of illustration only and are not to be taken as in any way limiting the scope of the invention.

In the drawings,

Fig. 1. is a schematic illustration showing two engines and controllable pitch propellers driven thereby, and electrically actuated devices for regulating the speed of the propellers and maintaining the propellers in synchronization with each other and,

Fig. 2 is a schematic illustration of an arrangement wherein two or more propellers are driven by the same engine and the thrust of the two propellers is equalized by suitable electrically actuated devices.

Referring to the drawings in detail and particularly to Fig. l, the two engines, schematically illustrated, are indicated by the reference numera-ls Ill and I2 and the controllable pitch propellers driven by the engines are generally indicated by the numerals l4 and I6 respectively. While only two engines and two engine-driven propellers have been illustrated,iit is to be understood that the application of the invention is not limited to any particular number of engines or propellers.

The controllable pitch propellers l4 and I8 may be of the feathering type, having rotatably mounted blades l8 provided with beveled gear sectors which mesh. with a pitch changing gear 20 rotated by power actuated means under suitable manual or automatic control. This invention contemplates changing the pitch oi the propeller blades by actuating the pitch changing mechanism by an electro-magnetic motor device comprising a wound field and a wound armature separately excited, which device will be herein- 5 after referred to as a "Selsyn" unit. Each Selsyn. unit has a relatively rotatable part or rotor 22 and a relatively stationary part or stator 24. For convenience in the explanation the Selsyn unit connected with the propeller I4 is generally designated by the numeral 28 and the Selsyn unit connected with the propeller I6 is generally designated by the numeral 28. I

Between the rotor 22 of each Selsyn and the pitch'changing gear 20 there is provided a suitable'reduction gear unit 30 having a reduction factor of the order of several thousand to one. The Selsyn ispreferably mounted on or in the forward portion of the propeller hub and is directly connected to the propeller blades through the reduction gear 30 and the pitch changing gear 20 and the blade carried gear sectors.

The propeller speed is regulated by some suit able form of constant speed device which may be a governor controlled engine but which, for the sake of convenience, has been shown as a constant speed electric motor connected with some suitable source of energy such as the battery 34 and provided with a manually actuatable speed controlling device such as the rheostat 36. This motor drives a three-phase alternating current v generator, generally indicated by the numeral 38, which includes a rotor portion 40 and a stator or field portion 42. The stator portion 42 of the alternator 38 is connected in parallel by means of suitable electrical conduits and three of thesix collector rings, generally indicated at 44, with the stator 24 of the Selsyn 2B and is similarly connected by means or three of thesix collector rings, generally indicated at 46, with the stator portion of the Selsyn unit generally indicated at 28.

Each of the engines drives a three-phase alternator, the one driven by the engine It being generally indicated at 48, and comprising a rotor portion and a field or stator portion 52-, while the alternator driven by the engine i2 is generally indicated at 54 and comprises a rotor portion 56 and a field or stator portion 58. The

stator of the generator or alternator 48 is connected to the rotor 22 of the Selsyn unit, generally indicated at 26. by means of suitable electrical conduits, and the three of the six collector rings 44 not used to connect the stator 42 with the stator 24. The stator 58 of the alternator 54 is similarly connected to the rotor of the Selsyn unit 28 by means of suitable electrical conduits and the corresponding three of the six collector rings generally indicated at 46. The

collector rings

44 and 44 are preferably mounted upon the propellor drive shaft between the propeller and the adjacent portion of the engine and are contacted by fixed brushes carried by the adjacent portion of the engine. They are preferably concentric and arranged in side by side relation with respect to each other and separated by suitable insulating materials. The rings and brushes and brush holders may be encased in an engine carried cover member in a manner well-known to the art.

With the above described arrangement the stators or field portions of the two Selsyn units 28 and 28 will be energized by the three-phase electrical impulses from the alternating current generator 38 driven by the controllable constant speed motor 32. The rotor portion of the Selsyn unit 28 will be energized by the three-phase alternating current impulses from the alternating current generator 48 driven by the engine l8 and the rotor portion of the Selsyn unit 28 will be energized by the three-phase alternating current impulses delivered by the alternating current generator 54 driven by the engine I2. If either one of the engines I8 or I2 tends to get out of synchronism with the constant speed motor 82, there will be a difference in the frequency and a change in the phase relation of the alternating current impulses energizing the stator and rotor portions of the Selsyn unit carried by the propeller driven by that engine, which frequency difference and consequent phase relation change will cause the rotor portion of the Selsyn unit to rotate relative to the stator portion of the unit thereby operating the propeller pitch adjusting mechanism to change the pitch of the blades of the respective propeller. This change in propeller pitch will alter the load on the engine and cause it to return to a condition of synchronism with the constant speed motor.

The speed of the constant speed motor 82 may be controlled by manipulation of the variable resistant rheostat 38 so that the two engines may be regulated to operate in synchronism with each other at any desired speed within the range of the apparatus.

In case a governed engine is used as the master speed control instead of the constant speed electric motor 32, the speed may be manually controlled by changing the setting of the governor on the governed engine.

At various times it may be desirable to place the propellers individually under manual control to change the pitch setting thereof or to bring the propeller blades into or out of a feathered condition. In the arrangement illustrated this may be accomplished by means of suitable manually operable switches located in convenient reach of the operator of the vehicle upon which the engines and propellers are mounted. The manually operable switches generally indicated at 88 and 82, are provided for the control of the propeller I4 while the similar switches, generally indicated at 84 and 88, are provided for the control of the propeller IS.

The switch ,88 is a double throw switch disposed in the circuit leading from the stator 52 to t1 e rotor 22 of the Selsyn unit 28 and has two opera tive positions in the first of which, as illustrated, it directly connects the individual windings of the stator 52 with the corresponding individual windings of the rotor 22, and in the other of which it disconnects the stator 52 from the rotor 22 and short-circuits some of the windings of the rotor 22 to convert the Selsyn unit 26 into an induction motor in a manner well-known to the art.

The manually operable switch 62 is a double throw switch disposed in the three electrical conduits connecting the individual windings of the stator 42 with the corresponding windings of the stator 24 and is operative to reverse the connection between the individual windings of the stator 42 and the individual windings of the stator 24 so that the induction motor, provided by shortcircuiting some of the windings of the rotor 22, may be caused to rotate in either direction to move the blades of the corresponding propeller I4 toward either a high-pitch or a low-pitch position. In this manually controlled pitch changing operation the generator 38 furnishes the power for operating the induction motor provided by short-circuiting some of the windings of the rotor of the Selsyn unit 28 and this power is transmitted through the reduction gear 38 to the pitch changing mechanism of the propeller.

The switches 64 and 66 operate in the same manner with relation to the Selsyn unit 28 and propeller I6 as the

corresponding switches

88 and 82 operate in connection with the Selsyn unit 28 and propeller I4 as explained above, and the generator 38 also furnishes the power for operating the unit 28 as a motor.

In the modified form of the invention illus trated in Fig. 2, the engine 88 drives a plurality of propellers, as generally indicated at I8 and I2, through suitable gearings generally indicated at I4.

In this case it will be obvious that the two propellers I8 and I2 will always rotate in synchronism with each other by reason of the interconnection between them through the gearing I4, and the condition to be maintained is an equalization of the thrusts developed by the two propellers. Each of the propellers I8 and I2 is a controllable pitch propeller incorporating pitch adjusting mechanism of a suitable form such as the intermeshing gear elements, generally indicated at I8 and 18, respectively, driven through

respective reduction gears

88 and 82 by respective propeller carried Selsyn units, generally indicated at 84 and 88. The Selsyn unit 84 comprises a rotor portion 88 and a stator portion 88 and the unit 88 comprises a similar rotor portion 82 and stator portion 84. The two

rotor portions

88 and 82 are connected, preferably through suitable slip rings, such as are indicated in Fig. 1, with the three phase wound stator 88 of an alternating current generator, generally indicated at 88, having a rotor portion I88, driven by the engine 88. The

stator portions

88 and 84 of the Selsyn

units

84 and 88, are connected, also preferably through suitable slip ring and brush connections, with the three phase wound stator I82 of an alternating current generator, generally indicated at I84, hav-' ing a rotor portion I88 driven by a constant speed motor I88 energized from a suitable source of energy such as the battery I I8 and manually controlled as to speed range by an adjustable rheostat H2.

With this arrangement, if the motor 88 gets out of synchronism with the master control I88 2. frequency difference will be created between the alternating current of generator I84 driven by the master control and the alternating current of generator 88 driven by the engine. Since the generators I84 and 88 are connected respectively to the

stators

98 and 84 and the

rotors

88 and 82 of the Selsyn

units

84 and 86, this difference in frequency between the alternating currents of simultaneously adjust the pitch of the two pro-' pellers to maintain th speed of the engine in synchronism with the speed of the master control while at the same time maintaining the pitch of the propellers the same so that the thrust developed by the two propellers will be equalized. It is to be understood, of course, that the same condition would apply regardless of the number of propellers driven by the engine. Provisions for manually controlling th propellers, similar to those described in connection with Fig. 1 may be made if desired.

While there has been schematically illustrated and briefly described two possible combinations of elements arranged according to the invention, it is to be understood that the invention is in no way limited to the arrangement so illustrated and described but that such changes therein may be resorted to as come within the scope of the sub- Joined claims.

Havingnow 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:

1. Speed control and. synchronizing means for h a plurality of controllable pitch propellers comprising respective electric units, each unit comprising an alternating current motor device hav- "ing separate relatively rotatable field and rotor portions, said rotor portion having a direct mechanical connection to the blades of the respective propeller for directly changing the pitch thereof, respectivealternating current generating devices each driven at a speed proportional to the speed of its respective propeller and electrically connected to one relatively rotatable portion of the corresponding electrical unit, and alternating current generating means driven at a controlled speed electrically connected in parallel to the alternativ relatively rotatable portions of all of said units.

2. In a control means for controllable pitchv propellers, an electrical unit comprising relatively gear carried by said propeller, said unit constituting the sole source of power for moving the blades in at least one direction to change their pitch, a master speed control, an alternating current generator driven by said master control and electrically connected with corresponding portions of all of said units, and individual alternating current generators driven respectively by the several propeller driving means and electrically connected to the other portion of each respective unit to render said units operative to change the pitch of the respective propellers whenever there is a frequency difference in the outputs of the generators connected respectively thereto, the output of each of said individual generators being at the same frequency as the output of said master control driven generator as long as the speed of the respective propeller is in synchronism with the speed of said master control.

4. In a thrust equalizing control for a plurality of coacting controllable pitch propellers having a common driving means, an electric motor unit comprising relatively rotatable separately excited portions carried by each of said propellers and having the rotor portion thereof mechanically connected with the pitch changing mechanism of the respective propeller a master speed control, analternating current generator driven 1 en by said common propeller drive and electrically connected in parallel to the rotor portions of all of said units.

5. Speed control and synchronizing means for a group of controllabl pitch propellers each having a hub and a plurality of blades rotatably mounted in said hub comprising, an electric motor device for each hub, each motor device having a wound stator element carried by the respective hub and a wound rotor element operatively connected with the respective hub supported blades, an alternating current generator for each rotatable portions carried by a propeller and connected with the propeller pitch changing mechanism solely by reduction gearing carried by said propeller, said portions being relatively moved by the eiIects of alternating current applied thereto,

and'constituting the sole source of power for moving the blades in at least one direction to change their pitch, a master speed control, means driven by said master speed control for applying a multi-phase alternating current to one relatively rotatable part of said unit, and means driven by the propeller driving means for applying a multi-phase alternating current to the ther relatively rotatable part of said unit, said two means being timed with respect to each other so that the two currents have the same frequency as long as said propeller is driven at a speed in synchronism with the speed of said master control.

3. In a speed and synchronizing control for a plurality of coacting controllable pitch propellers, an -electric motor speed comparing and pitch changing unit carried by each propeller and operatively connected with the respective propeller propeller driven at a speed having a fixed relation to the speed oi. the respective propeller and connected to one element of the respective motor device, and an alternating current generator driven at a reference speed and electricallyconnected in parallel to the other elements of all of said motor devices and respective manually operable switch means electrically'connected with its respective electric motor device and one of its energizing generators operative to convert said electric motor device between a condition in which it operates in response to a frequency difference in the two alternating currents supplied thereto and a condition in which it operates as a motor energized by a single supply of alternating current by varying the internal circuit of said unit and the, connection between said unit and the generator connected with said switch, and electric control means for controlling the operation of said unit when acting as a motor energized by a single supply of alternating current.

6. In combination, an engine driven controllable pitch propeller, an alternating current electric generator and means for driving the same for establishing a reference speed, an alternating current electric generator driven at a speed bearing a fixed relation to the speed of said propeller, and electrically operated means mounted to rotate with and operatively associated with said propeller and having a portion thereof directly mechanically connected with the blades of said propeller, and means electrically connecting said electrically operated means with both of said generators to supply the energy for changing the pitch of said propellers and to convert a frequency difference in the electrical output of said generators into a pitch change of said propeller to maintain said propeller speed in synchronism with said reference speed.

7. In combination with a controllable pitch propeller, an electrically actuated speed comparing unit carried by said propeller and mechanically connected with the propeller blades, for changing the pitch thereof, said unit supplying all the energy for changing the blade pitch in at least one direction, said unit having separately energized field and rotor portions relatively rotatable in response to a frequency difference in the alternating current supplied respectively thereto, a generator driven at a reference speed electrically connected with one part of said speed comparing unit, an alternating current generator driven at a speed proportional to the speed of said propeller electrically connected to the other portion of said speed comparing unit, and manually operable switch means electrically connected with said speed comparing unit and one of said generators operative to convert said speed comparing unit, between a condition in which it operates in response to a frequency difl'erence in the two alternating currents supplied thereto and a condition in which it operates as a motor energized by a single supply of alternatin current, by varying the internal circuits of said unit and the connections between said unit and said generators, and a switch for controlling the operation of said unit when acting as a motor energized by one of said generators.

ERLE MARTIN.