US1958261A - Indicator - Google Patents

Description

May 8, 1934.

w. J. BLANCHARD INDICATOR Filed Sept. 2. 1932 4 Sheets-Sheet l W0? 1 5L A/VCHA/PD HIS ATTORNEY ajy 1%, W34,

w. J. BLANCH-HARD 3 958261 INDICATOR Filed Sept. 2. 1932 4 Sheets-Sheet 3 IIIIIIIIH 7/ IZQ INVENTOR BY HIS ATTORNEY W 1934 W. .J. BLANCHARD INDICATOR Filed Sept. 2, 1952 4 Sheets-Sheet 4 INVENTOR WERNER flzA/va /A/P Patented May 8, 1934 mmcs'ron Werner J. Blanchard, Kenmore, N. Y., assignor to Curtiss Aeroplane & Motor Company, Inc., a

corporation of New York "Application September 2, 1932, Serial No. 631,437

' 12 Claims. (01. 170-163) This invention relates to aircraft propellers, and more particularly to improvements in control and indicating devices for propellers with controllable pitch blades.

The invention herein described is particularly useful in conjunction with a controllable pitch propeller such as that described in my copending application Serial No. 482,249, but it may likewise be used in conjunction with other controllable pitch propellers.

A controllable pitch propeller is generally considered as one in which the propeller blades may be rotated about their own axes forchanging pitch while the-propeller is in operation. Mechanism is provided within the propeller hub for efiecting the gradual rotation of the blades about their axes, this mechanism taking the form of .an electric motor or other source of motive power.

My invention consists generally of an indi- 2o, eating and control device remote from the propellerand conveniently available to the pilot or crew of an. aircraft. The indicating portion of the device serves to continuously register for the pilots information the precise pitch position of the blade. The control element of the device serves to govern changes in the pitch of the propeler blades according to the will of the pilot or crew. A particular feature of the control element of my device is its semi-automatic action, wherein the control element may be moved over the dial to pre-select a desired pitch angle for the blades. The associated mechanism thereupon automatically starts, moves the blade to the pre-selected position and stops its action upon arrival of the blades at such pre-selected position. Concurrently with the moving of the blades to a new position, the above mentioned pitch indicator continuously indicates the exact pitch at which the blades may be at any instant of their travel.

In other types of controllable pitch propellers, means have been provided for actuating the motive power for changing the propeller pitch. Likewise indicating devices have been provided for the visual representation of the blade pitch at any time. Applicant, however, is not aware of any control and indicating devices, which are semi-automatic in action, or which allow the pilot or crew of an aircraft to pre-select a desired pitch setting, after which no further attention is required on the part of the pilot-or crew; the mechanism being responsive in its action to the semi-automatic control member to effect the pitch change which may have been selected.

An object of the invention is to provide means for pro-selecting a new blade angle for a controllable pitch propeller, with associated mechanism for automatically effecting the pitch change which may have been pro-selected.

A further object of the invention is to provide means as above described, which is operable to either increase or decrease the pitch of the propeller blades. A A further object is to provide a pitch indicating device in conjunction with the above mentioned devices, which operates cooperatively with the pitch changing mechanism.

A further object is to provide such pitch changing and indicating ineans that will be compact, light in weight and simple in operation.

A further object is to provide a' pitch changing and indicating mechanism which is operative in conjunction withthat type of controllable pitch propeller which is operated electrically.

A further object of the invention is to provide a novel form of electro-mechanical indicating and control means.

Further objects will be apparent from a reading of the subjoined specification and claims and from a consideration of the accompanying draw ings.

My invention consists of a substantially cylindrical casing having on one end thereof a dial, and having therewithin operating mechanism. The dial is calibrated in any suitable manner,

- either in degrees of propeller pitch, in R. P. M.

of motor, or in some other manner. An indicating pointer is adapted to register against this dial and in conjunction with the propeller and the mechanism within the device is adapted to indicate the pitch of the propeller. A control handle is likewise adapted to move over the dial and may be operated manually to overlie anyone of the various indices on the dial, thus serving to pre-select a pitch setting to which it is desired to change the pitch of the propeller; Mechanism within the device, operating in conjunction with the control handle serves to close an electrio circuit, start an electric motor within the hub of the propeller, and cause a change in pitch of the propeller blades. Mechanism is likewise provided within the device so that when the propeller blades have changed pitch to the point preselected by the control member, the current of the electric motor is automatically turned ofi and the propeller pitch is established at the angle previously selected by the control member. During the change in pitch of the propeller blades, the indicating pointer moves across the ,dial

showing at all times the then current propeller pitch angle.

In order to explain the invention more clearly, an embodiment thereof is shown in the accompanying drawings, in which-similar numbers indicate similar parts, and in which:

Fig. 1 is a side elevation of the invention partly in section;

Fig. 2 is a front elevation of the invention;

Fig. 3 is a plan of the invention partly in section;

Fig. 4 is a section on the line 44 of Fig. 1;

Fig. 5 is a section on the line 55 of Fig. 1; 6 is a section on the line 66 of Fig. 1; 7 is a section on the line 7-7 of Fig. 2; 8 is a section on the line 88 of Fig. 1; 9 is a section on the line 9-9 of Fig. 1; 10 is a section on the line 1010 of Fig.

Fig. 11 is an enlarged portion of Fig. 8;

Fig. 12 is similar to Fig. 11, showing certain portions of the device in different positions of adjustment;

Fig. 13 is similar to Fig. 11, showing certain portions of the device in different positions of adjustment;

Fig. 14 is a section on the line 1414 of Fig. 11;

Fig. 15 is a section on the line 15l5 of Fig. 13;

Fig. 16 is a wiring diagram showing the electrical relation of the invention to the electrical motor forming part of the mechanism of a controllable pitch propeller; and

Fig. 1'7 is an elevation of a portion of a controllable pitch aeronautical propeller showing, diagrammatically, electric motor and gear reduction means for causing variations in the pitch of the propeller blades; electrical connections with which the device is adapted to be connected are also shown.

Referring to Figs. 1, 2, 3 and 7, the device comprises an outer cylindrical casing 20 having a mounting flange 21 at one end thereof, and a closure 22 at the other end thereof. In a recess 23 isfltted a dial 24 upon which indices 25 and corresponding index numbers are inscribed. A pointer 26 mounted on a hollow shaft '27 is adapted to register with the indices 25 on the dial 24 for indicating propeller pitch, by means of mechanism to be later described. A control handle 28 is mounted on a shaft 29 concentric with and bearing within the hollow of the shaft 27.

A pointer 30 is fixed rigidly to the shaft 29 to likewise register against the. indices 25 on the dial 24. Operation of the control handle 28 serves to pre-select propeller pitch, indicate the setting through the pointer 30, and cause operation of the mechanism to effect a change in pitch in a manner to be hereinafter described. A cover glass 31 is inserted in the casing 20 over the pointers 26 and 30 and under the control handle 28 to form a dust proof closure for the dial 24.

Referring more particularly to Fig. '7, the shaft 29, to which is attached the control handle 28, extends rearwardly through the rear closure 22 and is borne therein by a bearing 32. Fixed to the rearward end of the shaft 29, and pinned thereto by a pin 33, is a ratchet wheel 34 having around its circumference a series of teeth 35. The teeth 35 are so spaced circumferentially that the distance from the apex of one tooth to the apex of the next adjacent tooth,

corresponds to the distance between adjacent index marks 25 on the dial 24.

Referring more particularly to Figs. 1, 3 and 8, a spring-pressed pawl 36, pivoted as at 37 to the rear closure 22 is adapted to bear against.

the teeth 35 of the ratchet wheel 34. The engaging pcrtion 38 of the pawl 36 is formed with a rounded end so that, by overcoming the action of the spring 39 which presses the pawl 36 against the teeth 35, the ratchet wheel 34 may be rotated in either direction by turning the handle 28.

The ratchet wheel 34 carries on either side thereof perforated discs of insulating material as 40 and 41, these discs being fixed to the ratchet wheel '34 as by rivets 42. The inner disc 40 carries a pair of switch contact points 43 and 44, which contact points extend rearwardly through the insulating disc .41 in insulated relation to the ratchet wheel 34, and have attached at their rearward ends a pair of contact pieces 45 and 46 as shown in Figs. '7 and 9. The rear closure 22 carries on its inner surface a pair of concentric collector rings 47 and 48. These collector rings are attached to the rear closure 22 by rivets 49. ring 4''! has a screw passing rearwardly through the closure 22 to form an electrical terminal therefor. The inner collector ring 48 has a screw 51 passing through the rear closure 22 to form an electrical terminal therefor. The collector rings 47 and 48, and the screws 49 and 50 are in insulated relation to the rear closure 22, or the rear closure 22 itself may be fabricated from insulating material such as hard rubber or bakelite.

Referring to Figs. 7, 9 and 10, it will be seen that the contact piece 45 carried by the ratchet wheel 34 is adapted to continuously contact with theccllector ring 47 and that a continuous electrical path is provided from the screw 50 to the switch contact point 43. Likewise, it will be seen that a continuous electrical path is provided from the screw 51 through the collector ring 48, through the contact piece 46 and to the switch contact point 44.

Referring now to Figs. 11, 12, 13, 14 and 15, which are enlarged views of a portion of Fig. 8, a switch arm 52 is pivoted to the ratchet wheel 34 in such relation that the contact piece 53 at the inner end of the switch arm 52 may overlie and contact with one or the other of the switch contact points 43 and 44, or may lie therebetween in a neutral disconnected position. The switch arm 52 is provided with a pivot pin 53' and a compression spring 54, bearing at one end against a boss 55 mounted rigidly within the ratchet wheel 34., The other end of the spring 54 bears against a washer 56 retained in *fixed relation to the pin 53' by a key 5'7. Thus, the switch arm 52 is constantly drawn against the boss 55 by the action of the spring 54.

The boss 55 is provided with a pair of radial grooves 58 and 59. These grooves are arranged so that their axes are respectively in line with the switch points 43 and 44. The switch arm 52 is provided along its axis with a pair of round head rivets 60 and 61 which are adapted to seat in one or the other of the grooves 58 or 59. The pressure of the spring 54 thus tends to draw the switch arm 52 against the boss 55 and the round heads of the rivets 60 and 61 will tend to seat in either the groove 58 or 59, upon which, the contact end 53 of the switch arm 52 will engage either the switch point 43 or the switch point 44 for electrical contact.

The switch mechanism above described in conjunction with the control handle 28, serves The larger collector as the electrical switching meansfor turning the electric current on and oif for actuating the motor in the propeller hub.

Referring again to Fig. 7, an operating arm 62 is shown attached, as by rivets 63, to a flange on the rearward end of the hollow shaft 27. This arm extends radially outward to the point 64 and then extends rearwardly parallel to the shaft 29, andat its rearward end has a dog 65 engaging in a, notch 66 at the outer end ofthe switch arm 52. The rearward end of the operating arm 62 with its dog 65, and the method of engagement of the dog with the switch arm notch 66, is also shown in Figs. 11, 12, 13, 14 and 15. The operating arm' 62, with its associated hollow shaft 27 and indicating pointer 26, is adapted to be resiliently urged toward one or the other direction of rotation by a spring mechanism now to be described.

A spring drum 67 (see Figs. 5, 6 and 7) is fixed to turn with the shaft 29 by apin 68. The spring drum 67, as shown in section in Fig. 7, has a central web portion and outstanding circumferential flanges extending forwardly and rearwardly therefrom. Through the web portion of the drum 67, toward the outer edge of the web thereof are inserted a pair of spring anchors 69 and 70. Surrounding ihe shaft 29 and directly adjacent each side of the web portion of the drum 6'7 are located two ball bearings 71 and 72. On the outer face of the bearing 71 is mounted a disc 73 whose radius is such that the disc will lie within the boundary established bythe path of the spring anchors 69 and 70 as they rotate. A single dog 74 extends outwardly from the edge of the disc 73 so that, in a certain position of adjustment, to be later described, it may abutthe spring anchor 69 and the operating arm 62. A spiral spring 75 is adapted to be anchored at its inner end to the disc 73, said spring 75 being anchored at its outer end to the spring anchor 69 attached to the spring drum 67. A second disc 76 is mounted on the ball bearing 72 on the opposite side of the spring drum 67 from the previously mentioned disc 73, and carries the inner end of an opposilely wound spiral spring 75', the outer end of which is fixed to the spring anchor 70. This disc, like the disc 73, is of such radius that the disc may rotate withinthe path described by the spring anchors 69 and 70. The disc 76 has formed thereon a dog 77 which is engageable, in certain positions of adjustment, with the spring anchor 70 and with the operating arm 62.

The spring motor, the parts of which are above described, serves under certain conditions, to cause a resilient force to be impressed upon the operating arm 62, this force being sufficient; so that, when the opera ing arm 62 engages the notch 66 of the switch 'arm 52, there will be suificient tension to'cause operation of the switch, resulting in a making or breaking of electrical contact of the contact point 53 with one or the other of the switch points 43 or 44.

Before describing the functioning of the previously described elements in their relation one to the other, the parts and de' ail functioning of the escapement mechanism immediately behind the and likewise has a bearing point 83 in a bulk-' head 84 mounted within the casing and intermediate its ends. 'A toothed escapement wheel 85 is also mounted on the shaft adjacent the shaft 87 for oscillating motion. Said yoke 86 has a pair of upstanding arms 88 and 89, which, at their upper ends, are provided with escapement points 90 and 91, respectively, said points being engageable with the teeth of the escapement wheel 85. It (the escapement yoke 86) is resiliently urged toward one extreme position by means of a spring 92 attached at one end at a point close to the escapement point 90, and at the other end to a bar 93 rigid with the case20 of the device. Said yoke .is also provided with an armature member 94 attached to the upstanding arm 88, and which said armature member 94 is fabricated from a magnetic material such as soft iron. Attached to the bulkhead 84 is a pair of electromagnets 95, so located that when they are energized by an electric current, they magnetically draw-the armature member 94 toward their pole pieces. i

' Upon observing the funclioning of this escapement mechanism, it will be noted that a torsional force is transmitted to the gear 78 through the shaft 27 and the operating arm 62 from the spring motor previously menlioned. This torsional force tends to turn the escapement wheel 85, for example, in a counter-clockwise direction, resulting in the contact of a tooth 96 of the escapement wheel with the escapement. point of the escapement yoke 86. Such condition would exist when the electro-magnet is energized, resulting in the movement of the armature 94 and the escapement yoke 86 towhich it is attached in a direction to overcome the tension of the spring 92.

Upon cessation of the passage of an electric current through the electro-magnet 95, the spring 92 is allowed to draw the escapement point 90 away from the escapement wheel tooth 96, thus allowing the escapement wheel to turn slightly under the previously mentioned torsional force, until another tooth of the escapement wheel 85 comes in contact with the escapement point 91 of the escapement yoke. Upon re-energizing the eleetro-magnet 95, the escapement wheel 85 is allowed to turn an additional small amount to thu's permit rotation of the gear 78 by its engagement with the pinion 79. Hence, upon repetitious energizing of the electro-magnet 95, so. long as a torsional force is applied to the shaft'27 and the gear 78, the indicating hand 26 is allowed to travel over the dial 24.

Next, reverting to the functioning "of the device as a whole, it will be-seen that if the control handle 28 is turned, the ratchet wheel 34 will be turned a like amount and wil be retained in its new position by the action of the pawl 36. Concurrently with the turning of the ratchet wheel, the switch arm 52 will be twisted to disengage from the operating arm.62 and to cause contact of the contact ponts 53 with one or the other of the switch points. 43 or 44, according to the direction of rotation of the ratchet wheel 34. When such turning of the ratchet wheel 34.

is effected, the spring drum 67 is likewise turned.

Assuming that the control handle 28 has been turned in a counter-clockwise direction when viewing the devce from the dial end, tension will be caused in the spring 75 by the rotation arm 62. The tension in the spring '75 will, however, be transmitted through the disc 73 and the dog 74 to cause pressure in a counter-clockwise direction against the operating arm 62. Movement of the operating arm 62 is prevented by the restraining effect of the escapement m'echanism cooperating with the other end of the hollow shaft 29 upon which the operating arm 62 is mounted.

Under the conditions assumed, contact of the switch arm 52 with the contact point 44 will have been established, completing an electrical circuit through the collector ring 48' and the screw 51, completion of this electrical circuit a1- lowing for the starting of the motor within the propeller hub to cause rotation of the propeller blades about their respective axes.

Referring to Figs. 16 and-17, A represents a propeller hub having blades B and C projecting therefrom, the blades being adapted to rotate with respect to the hub about their longitudinal axes. The blades B and C are provided with bevel gears D and E, respectively; within the hub, sa-d gears engaging with a bevel gear F; the latter is adapted to be revolved by means of an electric motor G and a series of gear reduction units H, the motor and gear reduction units being contained in a housing I projecting forwardly from the propeller hub. The motor includes an armature 9'7. One brush, 98, of the motor is connected through a lead 99 to ground. The other brush 101 is connected by a lead 102 to one end of each of the field coils 103 and 104 of the motor. -The opposite ends of the field coils 103 and 104 are connected through a collector ring mechanism J of a conventional construction located between the propeller and the aircraft, by leads extending through the airplane to the indicating device. One end of the field coil 103 is connected by a wire 105 to the screw 51 of the device, whereas the corresponding end of the field coil 104 is connected by a wire 106 to the screw 50. v

The electrical connections within the device comprise wires 107 and 108 which lead from the electro-magnet 95 to the terminals 109 and 110 on the rear closure 22 of the device, Within the device, the uninsulated metallic parts, particularly the switch arm 52 are connected-to the terminal 110. Externally of the device, the terminal 110 is connected to a storage battery 111 carned within the aircraft, the other terminal of the storage battery 111 being grounded to the framework of the aircraft.

Within the propeller hub, and coacting with the armature 97 is a simple switch 112 having a rotary portion 113 electrically connected to ground and so organized that the rotary portion 113 rotates once for every one-half degree pitch change of the propeller blades. The ratio of the several reduction gear units H may be readily organized so that-a connecting shaft between two adjacent units is arranged to rotate once for each half degree of rotation of the propeller blades B and C about their longitudinal axes.

' To such a shaft, the rotary portion 113 is at- Q tached. Once during every revolution of the rotary portion 113, contact is made with a portion' 114 of the switch, which portion is connected by a, wire 115 to the terminal 109 on the device, whitfli said portion 114 is attached to and electrically insulated from the interior of the housing! by conventional means.

of the electrical connections, the control handle had been moved in a counter-clockwise direction and had established through the device, an electrical circuit for energizing the motor G in the propeller hub and housing I through the terminal 51 and hence through the field coil 103 of the motor. This energization causes rotation of the blades about their own axes by the action of said motor. Upon the gradual twisting of the blades, the switch 112 within the housing I is caused to contact at each one-half degree change of pitch. Such contact allows energization of the electromagnet 95, thus operating the escapement mechanism to allow rotation of the gear '78 and hence of the pitch indicating pointer 26. As the pitch changing action continues, the operating arm 62 moves with the indicating pointer 26 and gradually approaches the position at which the ratchet wheel 34 has previously been set. The operating arm 62 gradually comes into engagement with the notch 66 on the switch arm 52, and by the previously described torsional force provided by the spring provides the efiort necessary to move the contact point 53 from its engagement with the switch point 44. This immediately breaks the circuit which energizes the electric motor, upon which action the electric motor ceases to operate. Cessation of the operation of the motor likewise causes cessation of the action of the switch 112 within the housing I and causes cessation of the functioning of the escapement mechanism, bringing the whole mechanism to a point of rest.

Operation of the mechanism for reverse pitch changing of the propeller blades is entirely similar in principle to that outlined above, the only difference being that, when the operating handle 28 is moved in a clockwise direction, the switch arm 52 would be moved for contact with the switch point 43, energizing the field coil 104 of the motor for reverse rotation of the armature 97. The escapement mechanism and indicating pointer 26 would likewise be operated in a reverse direction by the tension imposed by the other spiral spring 75' held within the confines of the spring drum 6'7, and as the reverse pitch changing progresses, the operating arm 62 engages the notch 66 on the switch arm 52, the tension of the spring 75' disengaging the switch arm 52 from the contact point 43, resulting in the whole mechanism coming to rest at the pitch originally pre-selected by the operating handle 28.

It will be seen from the above description that the control elements of the device co-act with the indicating elements of the device to produce the results and objects previously set forth.

In operation of the device, in conjunction with an aircraft, the following will indicate how the device would be used in practice. When the aircraft is on the ground ready to take off, the engine is started and the pilot observes the revolutions per minute'of engine and propeller on his tachometer with the engine running at full power. The pilot knows from the performance data of the engine that maximum power is developed, for instance, at 2000 R. P. M. If the propeller on the ground rotates at 1600 R. P. M. with full throttle, he knows that full power is not being developed by the engine. He therefore moves the operating handle 28 on the device to reduce the blade pitch angle from 16, for instance, to 14?. This will result in an increase in R. P. M. of the motor on the ground. He may change the pitch of the propeller blades until the R. P. M. of the motor reaches a value of approximately 2000 a. P. M., at which speed he will know that he is obtaining full power for take-off. He then starts the airplane moving and takes off. As the airplane takes the air and gathers speed, the R. P. M. of the engine and propeller will tend to increase, since the movement of the craft through the air requires less pull by the propeller than in the original take-off condition. Realizing that such increased R. P..M. may be harmful to the engine and may result in excess fuel consumption, he then increases the pitch of the propeller blades by moving the operating handle 28 on the device to an index indicating a higher pitch angle. By the mechanism described, the pitch angle is automatically increased, whereupon the increased power required to turn the blades at their higher pitch angle setting will reduce the R. P. M. of the engine and propeller to a desirable value. Pitch changes may likewise be made in flight to obtain optimum conditions of air speed of the aircraft with relation to engine speed.

-The invention may be easily adapted to reversal of a controllable pitch propeller as applied to any aircraft, such'an application allowing for reversal'of the direction of travel of the craft without the necessity of incorporating reverse gears or a reversible engine in the propulsion system. Such use would be particularly advantageous in maneuvering dirigible balloons in the air, or in maneuvering seaplanes' on the water.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without de-- parting from;the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes. a

What is claimed is: 1. In pitch indicating and control means for a controllable pitch propeller, a unit device remote from and connected to said propeller for indicating the pitch of said propeller, said device having associated therewith a member for pre-selecting a new pitch setting, and mechanism responsive in its operation to movements of said member for automatically causing said change of pitch upon pre-selection thereof by said member.

2. In a pitch indicating and controlling device indices marked thereon, a pointer adapted to move across said dial for indicating the pitch of said propeller, a control member also adapted to move across said dial, and mechanism. associated with said device and connected to said propeller, said mechanism cooperatingwith said member for changing the pitch setting of said propeller upon any change in the position of said member, and said pointer being adapted to move to and register on the same index as'the one on which said member registers as said propeller reaches the pitch corresponding to the index on which said member is set.

4. In pitch indicating and control means for a controllable pitch propeller having associated therewith an electric motorfor v changing the pitch thereof while said propeller is in operation, an electrical device connected with said propeller, said device including a dial and indicator, and mechanism associated with said device for moving said indicator'with respect to said dial as a change in pitch setting of said propeller is eiTected by saidelectric motor.

5. In pitch indicating and control means for a controllable pitch propeller having associated therewith an electric motor for changing the pitch of said propeller while'in operation, an electrical device connected with said motor, said device including a dial, a control member movable across said dial, mechanism associated with'said member for causing an electric current to pass through said motor as said ;member' is moved across said dial, said mechanism being adapted to automatically turn off said current when said propeller pitch has been changed by said motor to a pitch corresponding to the position to which electric motor within said propeller responsive in operation to said electric circuit, a switch responsive in its operation to the motion of said electric motor, a second circuit controlled by said switch, and electro-mechanical escapement means responsive in its operation to said second circuit,

said escapement means beingorganized to break said first mentioned electric circuit in certain positions of adjustment of said switching mechanism. 1

'7. In a pitch indicating and controlling device for aeronautical propellers;-a pre-settable conblades for moving said actuating means, and;

mechanism responsive to said follow-up means for causing the cessation of movement of said actuating means upon attainment by the propeller blades of the desiredpitch preset by said control member. v

8. In a-pitch indicating and controlling device for an aeronautical propeller having motive means for changing the blade pitch thereof, a

pre-settable control member, mechanism actuated by said control member for actuating said motive means, followup means responsive in its operation to movements of the propeller blades after the indicated movement may have been started, said follow-up means being associated with said actuating means and adapted to act.

to de-energize said motor when the pitch preset a pre-settable control member, a switch actuated thereby for energizing said motor to initiate and accomplish a change in pitch of the blades, a second switch associated with the propeller blades and organized to' energize an electrical circuit intermittently as the blades are changing in pitch,

an electro magnetic escapement device responsive to said circuit, and means connecting said escapement device with said first mentioned switch for opening said switch and de-energizing said motor upon attainment by the propeller blades of the pitch preset by said control member.

12. In a pitch indicating and controlling device for controllable pitch propellers, a unitary instrument comprising a dial, a member adapted to be moved over said dial, mechanism within said instrument responsive to actuation of said member for acting on said propeller to effect pltch' changes, and a hand also movable over said dial and connected in part with said mechanism, organized to at all times indicate the true pitch setting of the propeller blades.

WERNER J. BLANCHARD.

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