US2411290A

US2411290A - Machine gun synchronizer

Info

Publication number: US2411290A
Application number: US316999A
Authority: US
Inventors: George W Pontius
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1940-02-02
Filing date: 1940-02-02
Publication date: 1946-11-19
Anticipated expiration: 1963-11-19

Description

Nov. 19, 194e w, pbNTlus, D 2,411,290

MACHINE GUN SYNCHRONIZER Filed Feb. 2, 1940 5 Sheets-Sheet l INVENTOR- G% OQ.GE \zJ- owrws 1H3 AT RNEY.

5 Sheets-Sheet 2 INVENTOR. GEIOQGE Ml. WONT 05 G. W. PONTIUS, 3D

MACHINE GUN SYNCHRONIZER Filed Feb.' 2, 1940 Nov. 19, 1946.

NOV. 19, 1946. 3 w -nus, 313 2,411,290

MACHINE GUN SYNCHRONI ZER Filed Feb. 2, 1940 5 Sheets-Sheet 3 NOV. 19, 1946- G. w -PONT|Us 35 .2,411,290

MACHINE 'GUN SYNCHRONIZER Filed Feb. 2, 1940 5 Sheets-Sheet 4 W25 ms:

INVENTOR H 05 1111 GeoQeE- J. 'PON NOV. 19, 1946. 3 w, po U 3 2,411,290

MACHINE GUN SYNCHRONIZER Filed Feb. 2, 1940 5 Sheets-Sheet 5 INVENTOR. GEQQQEN; 'DOMfluS BY I k u Patented Nov. 19,1946

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MACmE GUN SYNCHRONIZER Application February 2, 1940, Serial No. 316,999

18 Claims.

This invention relates to a synchronizer for firing a machine gun through the propeller of an airplane and to actuating mechanisms for firing a gun.

In military aircraft, although guns may be mounted in the wings, it is also desirable to mount guns on the fuselage to fire forward in the direction of flight of the aircraft. This means in the case of a single motored airplane that the guns must be fired through the arc of the propeller of the airplane, necessitating synchronization of fire with the propeller to prevent the propeller from being hit. In firing a gun through a propeller, account must be taken of the time required for a bullet to reach the propeller zone from the instant of firing pin actuation. The adjustment of firing to engine rotation which is proper for low speeds of propeller rotation may be entirely wrong at advanced speeds of rotation when the propeller blade may possibly be in the path of the bullet before the bullet reaches the propeller zone. This defect of adjustment is especially true when three and four bladed propellers are used.

This condition is not so much of a problem when a two bladed propeller is used, because the speed of emergence of a bullet is such in relation to propeller rotation that a fixed firing point on the propeller arc will in most cases give ample clearance at all propeller speeds. However, the use of three and four bladed propellers makes the available firing arc so small with relation to the speed of emergence of a bullet that a fixed firing instant cannot be used, and a variable firing instant must be employed for varying propeller speeds.

Centrifugal adjusters have been used to advance the impulse generator shaft over the driving shaft. However, these centrifugal adjusters are affected not only by the speed of propeller rotation but by the load which the adjustment must transmit. Thus where the propeller is operating at a high speed, the centrifugal adjusters will assume a corresponding position. But when the machine guns are fired, the work of trigger actuation must pass through the centrifugal adjuster, which then assumes a position dependent upon the load transmitted and the propeller speed. This condition is accentuated by the large numbers of machine guns now used at times on a single airplane, which may be four or more.

It is therefore an object of this invention to provide a synchronizer which advances firing impulse generators in proportion to the engine speed alone, and which is independent of the load transmitted. Another object is to provide a synchronizer employing a controlled power unit to advance the impulse generator.

It is an object of this invention to provide a centrifugal control for such a power unit, and

' further, to provide a centrifugal control free from the influences of acceleration or deceleration of the aircraft in which the synchronizer is mounted.

A further object is to provide a new type of trigger motor for machine gun actuation. Also it is an object to provide flexible drive means for said trigger motor. Still another object is to provide a novel lockout and engagement device for machine gun trigger motors.

It is a feature of the invention that the trigger motors may be mounted on the gun at any angle thereto according to the most beneficial method of leading the impulse transmitting mechanism to the trigger motors.

Other objects and features of the invention will be apparent in the following description and claims, best understood when taken in conjunction with the accompanying drawings, in which:

Figure 1 is a view in elevation of an airplane with a part broken away to show machine guns actuated by apparatus constructed according to the invention;

Figure 2 is an enlarged sectional view of the automatic timing and advance mechanism shown at 24 in Figure 1;

Figure 3 is a detail view of the rocker arm 38 of Figure 2;

Figure 4 is a view of an alternative cam means for valve actuation; I

Figure 5 is a sectional View in elevation of a modified form of synchronizer; I

Figure 6 is a view in vertical section of a modified form of compensated governor control;

Figure 7 is a detail sectional view of a modi- I fied form of trigger motor employing a wedge lockout mechanism;

Figure 8 is a detail sectional view of a modified form of trigger motor with a slidable cam actuated by a hydraulic motor Figure 9 is a detail sectional view of a modified form of trigger motor with a movable tappet for a lookout; and

Figure 10 is a detail View in elevation of another form of compensated governor control. p

The invention is shown in Figure 1 as applied to an airplane IE1. A radial motor [2 covered by cowling l4, drives a propeller I6. At the rear of the engine, a power take-01f shaft acts through matching bevel gears to drive a shaft 22 which actuates the automatic timer mechanism enclosed in a housing 24. The power take-oil" shaft is geared to the crankshaft of the engine, which drives the propeller.

The airplane is equipped with a plurality of machine guns 26, arranged symmetrically on either side of the engine. Mounted on the sides of the guns are trigger motor units 28 driven by rotary flexible shafts 3B which are driven from the synchronizer unit 24. Since the fuselage of the airplane is smaller than the arc of the propeller, the guns must fire through the arc of the propeller, being mounted to shoot on a longitudinal line through the airplane fuselage, which is the direction of straight line flight.

The means which I provide to advance the. ar in instant in accordance with th speed of the propeller is the automatic timing and advance unit shown at 24 in Figure 1. This synch-ronizcr unit is shown in detail in Figure 2. A bevel gear [8 on a power take-off shaft driven by the engine [2 meshes with a bevel gear secured to a drive shaft 22, which in turn operates the synchronizer unit. The drive shaft 22' is mounted in bearings 32 secured to the housing 24. Near the forward bearing 32 a gear 34 is secured to a drive shaft 22 and drives gears 38 which rotate two parallel governor shafts 36.- The governor shafts 36 are mounted in suitable bearings attached to the housing 24. Mounted on the governor shafts are flyball governor units lil, stretched by springs t2. Each shaft has a rotatable collar ie which rides the free end of each of the flyball governors, and is held axially by ball bearings 45,

A rocker arm 48, shown in detail in Figure 3, contacts collars at through yokes on either end. The rocker arm 48 is pivoted on bolt lta at its mid section, secured to casing 24. Fingers E5 on the yokes of rocker arm 63 contact collar A l of the flyball governors 68, and cause rocker arm it to pivot on its bolt as the fiyball governors 39 assume different positions. A connecting rod 52 is pin jointed to the rocker arm 48 and to a hydraulic valve 54. The movement of the rocker arm 48 responsive to the governors t!) causes connecting rod 52 to actuate hydraulic valve 56. which controls and operates the power unit for the system, which unit will be later described.

I provide means to advance an impulse generator for firing the guns, to secure an advanced firing instant as the propeller speeds increase. This advancing means is in the form of an adjustable cam connection between a drivin shaft and a driven shaft. The inward end of the drive shaft 22 is enlarged and cut to form a helical gear 68. Coaxially, and a short distance therefrom is a helical gear l0 with a reverse helix. Gear 1! is attached to a shaft 12 to which is secured a generator gear '14. A sleeve 76, cut internally with helices to fit the helical gears 53 and i2, is fitted over the gears 68 and it. As'this sleeve it is moved axially in either direction along the drive shaft, the gear 'Hl will change its relative rotary position with respect to gear 68. The sleeve 75 is moved axially in either direction by a yoke member 18, pivoted to the housing 24 at 89. The yoke fits a groove on a collar ll rotatably mounted on sleeve 16, and thereby moves the sleeve along the drive shaft axis. The yoke member 78 is moved about its axis by a power unit which will next be described.

The power unit is a piston-cylinder lmit operated by hydraulic fluid under pressure. A piston rod 64 is securely fastened to the casing 2 3, and retains a piston 62 on the other end. A floating cylinder 56 is mounted on the piston rod 64 and casing moves also.

slides thereon. An integrally formed valve 5 controls the flow of fluid to the cylinder 55 and is connected to the cylinder through passages 55 and 58 at either end. Hydraulic fluid at times enters the valved i through three flexible conduits 8f, the two outside ones being pressure lines and the middle one being an exhaust line. The valve 54 is connected to speed responsive rocker arm as. The power cylinder 56 is pin jointed at 82 to the pivot arm 73 by a link 86. As the power cylinder 55 moves back and forth on its piston rod 84, it causes the yoke member 58 to move about its pivot Bil andthereby causes the sleeve "it to move axially.

I also provide means for converting the rotary motion of driven shaft E2 into firing impulses to fire the guns 2+3. Spaced about the generator gear 14 are motor gears M which drive axially flexible shafts 39 in a l-l ratio. These shafts pass through the housing 24 to their respective guns to actuate the trigger motors 28. If there were only one gun, its flexible shaft could be directly connected to shaft 12. One of the trigger motors is shown in detail in Figure 7. Each trigger motor 28 comprises a base lfil rigidly secured to its gun 26 opposite the position of a sear pin 95 of the gun 2G. The base [Ell retains a solenoid 96 for control of a lockout mechanism and is adapted to retain a turret top 9! which retains a cam 9G. The turret top 9! may be turned in any direction which is most suitable for placement of the rotary shafts 30. The'cams 536 are driven by the flexible shafts 3i] and are retained in bearings of any suitable kind in the turret top 9 I. The number of lob-eson the cam should correspond to the number of blades on the airplane propeller. The cam 9%: acts through a wedge 92 to actuate tappet 96 which actuates the sear pin 95 of the gun trigger mechanism. The tappet 9A is urged outward by spring 93 to return it to a perpendicular position if it should be encountered in a firing position by sear pin 95 upon counter recoil.

I provide means associated with the trigger motor for stopping the fire of the gun, which means I refer to as a lookout mechanism. The lockout mechanism comprises means for moving the wedge 92 forward and backward or right and left respectively with reference to Figure 7. When the wedge is pulled forward, the cam acts through the wedge 92 to fire the gun. But when the cam is in its rearward position the cam cannot actuate the tappet 94, and the gun does not fire. The wedge may be moved by a solenoid, or a hydraulic piston, but is illustrated as moved by a solenoid unit 86 acting through rod 98 to move the wedge. A spring we returns the wedge to the no-firing position when the actuation is released. The controls for the unit 33 are in the pilots cockpit.

In operation, the airplane engine if? turns shaft 22 through gears 18' and 26', and through the gears 34 spins the fiyball governor units ii), which assume definite positions for a given engine speed. The rocker arm 48 follows the movement of the governors and pulls on red 52 causing. the valve member to pull out, and valve 54 then passes high pressure liquid to the forward, or right hand, part of cylinder 5%. Piston rod 6d being fixed. the cylinder moves to the front (or right) and since the valve 54 is integral with it, the valve This movement will finally close the valve and bring the cylinder to a stop by cutting off the source of fluid. By using a liquid under pressure as the power fluid, there is no tendency to continue movement fluid is out 01f.

Meantime the cylinder has acted through rod 56 to move the yoke arm I8 and cause sleeve 16 to move axially to the front. This movement acts through the driving gear 68 to shift the driven gear 16 relative thereto and advance the generator gear Hi with relation to the drive shaft 22. The motor gears will now cause the trigger motors 28 to fire at an advanced point and thus prevent the bullets hitting the propeller as the speed of the propeller increases.

If the airplane motor should now slow down, the springs 42 move the collars 45, causing rocker arm 48 to reverse its direction of angular motion. Connecting rod 52 then pushes the valve member inward. This causes valve 54 to pass fluid to the left or rear part of the cylinder 56, causing it to move rearward. In doing so, the valve casing 54 moves with it until the valve is closed. Meantime the rod 6:; acts on lever T8 to shift sleeve 16 to change the relative positions of gears 63 to ill, according to the engine speed and retard the generator gear l4 and flexible shafts 36 relative to shaft 22. The trigger motors now fire at a more retarded point on the arc of the propellers and thereby effectively relate the firing to propeller speed.

The operation of the trigger motor described in connection with the synchronizer unit and shown in Figure 7 is as follows: The generator gear 14 of the synchronizer unit (Figure 2) drives gears 84 which are fastened to flexible rotary shafts 38, which lead to trigger motors 28. The relation of these parts is shown in Figure 1, wherein the synchronizer unit is represented by 2 At the trigger motor, the triangular cam 98 is fastened to the end of the flexible shaft after the and is rotated by it. The cam acts through the wedge 92 to reciprocate tappet 96 against the compression of spring 93. The tappet 94 strikes sear pin 95 and fires the gun in synchronism with the propeller, the lobes of the cam 98 corresponding in number and arrangement to the blades of the propeller it of the airship. To stop fire, the pilot of the airship opens the switch to solenoid 8 6, and spring I06 pushes the wedge 92 to the left, reducing the stroke of the tappet 94 so that it cannot fire the gun 2E.

The dual system of flyball governors is used to eliminate the effects of acceleration and deceleration of the aircraft, especially important in maneuvering. As the craft decelerates, the forward flyball governor will tend to pull the rocker arm toward it. At the same time the rearward flyball'governor will tend to push the rocker arm away from it, setting up equal and opposite forces in the rocker arm and neutralizing the effect of the deceleration. The forces in acceleration act in the same manner to neutralize the adjustment at the position for the respective rotativespeeds. In this manner the effects of acceleration and deceleration, such as would affect a single flyball governor, are eliminated. Acceleration and deceleration in planes transverse to the fuselage will have no effect on the governors since the fiyballs are revolving in those planes. 7

By using a power medium to advance the gen erator shaft, the centrifugal governor will reflect only the rotative speeds of the aircraftengine and will not be influenced by load factors. Thus the synchronizer can be made to operate very accurately and give definite assurance of faithful service.

The use of rotary flexible shafts to drive trigger motors results in freedom of placement of the guns and simplicity of installation of the firing mechanism. The rotary cam of thetrigger motor may have more or fewer lobes or multiples thereof, depending upon the number of blades in the propeller. This type of trigger motor is simple and reliable as well as being light in weight, all prime factors in aircraft.

An alternative means of actuating the valve 53 is shown in Figure 4. The rocker arm s3 is mounted on a rotatable cam shaft 50 secured to the synchronizer casing 2 3 by bolt 45. The drive shaft 22 passes through the centerline of rocker arm 48. A cam 53 is integrally formed on the camshaft 5i) and is adapted to contact the valve 54 (shown by a dotted line in Figure 4). As the rocker arm is rotated by the governors, the shaft 50 causes cam 53 to actuate the valve 55. A spring mounted in the valve may be used to keep the valve member in contact with the cam 53.

The operation of the modification shown in Figure 4 is as follows. Varying positions of rocker arm t8 according to engine speeds, turn shaft 58 and cause cam 53 to actuate the valve. The spring urged valve member may be used to keep contact with cam 53. The follow-up motion of the valve and the synchronizer actuation are the same as in the other embodiments of the system. I

A variation of centrifugal governors compensated for bodily acceleration and deceleration of the system is shown in Figure 6. Mounted on a shaft 522, driven by the engine, are centrifugal governors 540 driven through collars 542 attached to the shaft. The free ends of the governors terminate in members 544 having reversed helices and which are driven by the governors. The members 5 54 are connected by a unitary member 546 which mates the helices of each member 564. The connecting member is free to rotate but not move axially, being held by guide 548 acting in a groove on connection 545. A yoke member 558, riding groove in one of the members 564 actuates a proper power unit such as valve 5 5 and cylinder 56, and is movable according to ro-tative speed.

In operation, variation of speed causes the governors 540 to fly outward or contract, which pulls and pushes helices 544 in and out of connection 546, spinning connection 545 or deceleratin it, according to the axial direction of movement. When the system is bodily decelerated or accelerated, one helix will try to pull out of the connection 546 and the other will try to push in. The movement of each Will tend to twist the connection 546 to resist movement of the other, keeping the governors in their rotation responsive position, the axial inertia force of the system being taken through support 548. It will be appreciated that the governors need not rotate coaxially; all that is required are substantially parallel axes with the governors connected by an idler gear of proper matching shape for the helices.

Another embodiment of centrifugal governor controls is shown in Figure 10. A drive shaft 922 is connected to the engine drive of the aircraft.

Pinned to this shaft 922 is a governor bracket 924,

which retains two spaced, single arm flyball members 92B, pivoted at 928. Arms 930, depending from flyball members 926, contact a circumferential groove 932 in an axially movable sleeve 934. At the other end of the sleeve 934 is another governor bracket 936, splined to shaft 922 by splines 938 and free to move axially. Two flyball units 926 are mounted in a similar manner as those at-- 7 tached to bracket 924 and contact rear or left groove 932 of sleeve 934. The pairs of fiyball governors are preferably mounted so that the fiyball units are interfitting to shorten the axial length of the unit. A collar 9 5i holds a spring 942 against bracket 936, forcing it toward bracket 924. A groove 944 in bracket 935 moves lever 925, which controls a suitable power unit 948, which is used to advance and retard the driven shaft in relation to the driving shaft of the synchronizer unit.

In operation, the aircraft engine rotates shaft 922, rotating fiyballs 925. The forward ilyballs 926 fiy outward and force sleeve 934 to the left. Meantime the rear or left flyball 92B fly outward and press against sleeve 934, but being axially movable they move bracket 936 toward the rear against spring 942. In this manner, bracket 935 moves axially twice as far as would be the case with one fiyball group, represented by the axial movement of sleeve 934. bracket 934 actuates lever 94% and this in turn operates power unit 948. The effect of deceleration or acceleration of the aircraft on the synchronizer system is neutralized by cooperation of the pairs of flyballs.

Many modifications of power units can be used in the system. One modification is shown in Figure 5, wherein a centrifugal governor controls a valve coaxial with the drive shaft. A governor 24b is mounted coaxially on the drive shaft 222. This governor unit could be compensated for bodily acceleration and deceleration of the system as in Figure 2, by a connection to a non-axial governor unit, but is shown as an uncompensated governor unit. The movable end of the governor is attached to a coaxial valve member 254 adjusting it according to the rotative speed. An actuator member 246 contains internal helical grooves which fit the helical grooves on a coaxial stationary member 248 attached to casing 24 by support 258.

The actuator member 246 has an arm 252 extending from it. Between the casing 24 and the arm 252 is a power cylinder 256 having its piston rod attached to arm 252. he cylinder is attached to casing 24 at its other end.

Flexible conduits

250 and 258 connect the power cylinder with the valve passages. As the power cylinder acts on arm .252, actuator member 256 is rotated on helically rooved member 248 to advance the actuator member axially. Through an extension 262, a collar 216 is moved relative to the helical gears 268 and 2'78, advancin gear 218 relative to gear 268 thus advancing gear 2Hl. This advances the instant of firing through a firing motor mechanism not shown.

In operation, the governor 24G pulls valve member 254 outwardly, causing fluid to flow to the power cylinder drawing arm 252 toward the ca"- ing 24. This-advances member 246 on the shaft, eventually cutting off the fiuid supply. As the member 246 advances, collar 255 is drawn with it, advancing the generator shaft over the drive shaft 222.

Many modifications of trigger motors can be used in the system. One modification of the trigger motor is shown in Figure 8. A base I I9 is mounted on the gun 25. The base H0 retains a tappet IE2 urged outwardly by a spring H4. The tappet is adapted to actuate the sear H6 of the trigger mechanism of the gun. The base I H) is round toward the outer side, so that the actuating mechanism may be mounted at any angle to the gun.

The actuating mechanism is enclosed in a housing I I 8, having a removable cover I I 9, fastened to base I I 0 by a split collar I tightened by bolt I22.

The movement of IA rotary shaft I28, having a splined end 729, is protected by a casing I39, which is fastened to housing H8 by a nut I32. Fastening casing I30 to housing TIB retains shaft I28 in th housing I I 8. A shaft I26 is recessed and internally splined at one end and reduced at the other. This shaft fits over the splined member I29, compressin a spring I34 between them and rotates in housing MB. A cam I24, mounted on an offset sleeve I25, fits over shaft I255. The sleeve I25 is radially and regularly notched at the end of small internal diameter, and mates a similarly notched sleeve 12! having different numbers of regular, radial notches on the other face. Another notched sleeve I39 is splined or keyed to shaft I25 and has notches matching this other face of sleeve I21. A bolt I3I screws into shaft 726 and tightens the sleeves I39 and 121 against the offset of sleeve I25, the cam being driven through the key of sleeve I39. A piston packing I33 is attached to the outer end of sleeve I39. A hydraulic tube I36 is held in housing H8 by a tube nut 73?.

In operation, in a non-firing position, the spring I34 urges the cam I24 to the left, where it rotates without striking tappet H2. The gun at this time is not firing because the trigger mechanism is not actuated. When the pilot of the aircraft desires to fire the gun, he opens a hydraulic valve electrically or manually, allowing fluid to flow through conduit I38 and into housing I I8. This fluid then acts against packing I33 to compress spring I34, and force the cam I24 into operating position. Release of the fiuid pressure causes the cam I24 to return to a nonoperating position. This cam engaging mechanism could be a solenoid.

If, during operation, the tappet H2 should be depressed in the firing position, and the breech bolt should be in counter recoil, the sear H6.

would contact the tappet H2. If the tappet did not yield, the sear H6, being resisted, would fire the gun, thus giving an unsynchronized shot. To avoid this, the base H0 is recessed as at H5 so that sear H6 will force tappet II2 forward. When cam I24 turns past the firing position, the spring H4 will return the tappet II2 to a firing position opposite sear H6. Then the next impulse from cam I24 will fire the gun.

The sleeves I39 and I21 with their differently numbered notches are provided in order to get a very close and accurate adjustment of the cam I24 on the driving shaft I28. By removing tube screw 731, a screw driver may be inserted into casing H8, and screw I3I can be unscrewed, allowing sleeves I21 and I25 to be turned relative to sleeve I39. This is done by removing cover plate H9 and setting the airplane propeller at the proper position with relation to the gun to be fired, and then lacing cam I24 so that the tap-pet H2 is depressed or about to be depressed. I-laving secured this desired position, screw I3I is now tightened and the three sleeves locked in place with relation to shaft I26. The different numbers of notches on the sleeves allows a micrometer or vernier adjustment of the cam which is very sensitive. parts, this adjustment may be made very simply and readily.

Another embodiment of a trigger motor is shown in Figure 9. A base plate Bib retains a tappet block 8I2 containing a tappet M4 and a spring SIS. A spring biased solenoid 8H3 moves block 8I2 backward against spring 820 and spring 82!] moves it to a non-firing position upon release of the solenoid. The cam actuation is enclosed Because of the accessibility of the.

ma turret housing 822. en it is desired to fire the gun, the solenoid M8 is energized'pushing block 8l2 into position and the cam motor fires the gun through tappet 8M. Deenergizing solenoid 818 allows spring 820 to return block 8!! to the non-firing position.

Although the invention has been described with reference to particular embodiments of the invention, it is not limited to such embodiments, nor limited in any other manner, except by the terms of the following claims.

I claim:

1. In a device of the class described, a driving member, a driven member, a longitudinally movable spiral cam connection for connecting the driving member to the driven member for rotative movement and for advancing or retarding the driven member with respect to the driving member, fluid power means for moving spiral cam connection, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of flyball mechanisms responsive to the angular velocity of the driving member and non-responsive to the longitudinal acceleration of the driving member, and including a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

2. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving shaft to the driven shaft for rotative movement and movable to advance or retard the driven shaft with respect to the driving shaft,

fluid power means for moving the connecting means axially for retarding or advancing the driven shaft, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of opposed flyball mechanisms, and including a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

3. In an aircraft gun synchronizer, a driving shaft, a driven shaft, a longitudinally movable spiral cam connection for connecting the driving shaft to the driven shaft for rotative movement and for advancing or retarding the driven shaft with respect to the driving shaft, fluid power means for moving the connection axially for retarding or advancing the driven shaft, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of opposed flyball mechanisms, and including a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

4. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving shaft to the driven shaft for rotative movement and movable to advance or retard the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, said power means including a stationary piston and a cylinder movable in follow-up in accordance with the position of said valve, a control for said valve and power means including a pair of opposed flyball mechanisms, and including a member movable in response to the movement 'of the flyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

. 5. vIn a device of the class described,'ia driving ill member, a driven member, means for connecting the driving member to the driven member for rotative movement and movable to advance or retard the driven member with respect to the driving member, fluid power means for moving said means, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of parallel' shafts drivably connected to the driving member, a flyball mechanism mounted on each shaft in opposed relation and responsive to the angular velocity of the driving member and nonresponsiveto the longitudinal acceleration of the driving member, and a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid to the "fluid power means,

6. In an aircraft gun synchronizer, a driving shaft, a driven shaft, a longitudinally movable spiral cam connection for connecting the driving shaft to the driven shaft for rotative movement and for advancing or retarding the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of parallel shafts drivably connected to the driving shaft, a flyball mechanism mounted on each shaft in opposed relation, and a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means,

7. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving. shaft to the driven shaft for rotative movement and movable to advance or retard the driven shaft with respect to the driving shaft, fluid power means for moving the connecting means axially for retarding or advancing the driven shaft, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of parallel shafts drivably connected to the driving shaft, a flyball mechanism mounted on each shaft in opposed relation, and a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

8. In an aircraft gun synchronizer, a driving shaft, a driven shaft, a longitudinally movable spiral cam connection for connecting the driving shaft to the driven shaft for rotative movement and for advancing or retarding the driven shaft with respect to the driving shaft, fluid power means for moving the spiral cam connection for retarding or advancing the driven shaft, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of parallel shafts drivably connected to the driving shaft, a flyball mechanism mounted on each shaft in opposed relation, and a member movable in response to the movement of the flyball mechanisms for opening the valve to admit fluid to the fluid power means.

9. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving shaft to the driven shaft for rotative movement and movable to advance or retard the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, said power means including a stationary piston and a cylinder movable in follow-up in accordance with the position of said valve, a control for said valve and power means including a pair of parallel shafts drivably connected to the driving shaft, a fiyball mechanism mounted on each shaft in opposed relation, and a member movable in response to the movement of the fiyball mechanisms for opening the valve to admit fluid to the fluid power means.

10. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving shaft to the driven shaft for rotative movement and movable to advance or retard the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, a control for said valve and power means including a pair of opposed centrifugal mechanisms secured to the driving shaft and each having an axially movable part terminating in a'helix of opposite hand from that of the other, a rotatable but longitudinally stationary coupling matching and connecting said helixes, and a member movable in response to the axial movement of one of the centrifugal mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

11. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving shaft to the driven shaft for rotative moves ent and movable to advance or retard the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, said power means including a stationary piston and a cylinder movable in follow-up in accordance with the position of said valve, a control for said valve and power means including a pair of opposed centrifugal mechanisms secured to the driving shaft and each having an axially movable part terminating in a helix of opposite hand from that of the other, a rotatable but'longitudinally stationary coupling matching and connecting said helixes, and a member movable in response to the movement of the fiyball mechanisms for opening the valve to admit fluid under pressure to the fluid power means.

12. In a device of the class described, a driving member, a driven member, means for connecting the driving member to the driven member for rotative movement and movable to advance or retard the driven member with respect to the driving member, a servo motor for moving said means, a valve for controlling said servo motor, a centrifugal control for said valve and servo motor, said control comprising a governor shaft driven by said driving member, an axially movable sleeve mounted on the governor shaft, a first flyball mechanism secured to the governor shaft and operative to move the sleeve axially, an axially movable second fiyball mechanism rotatably connected to said governor shaft operative to tend to move said sleeve in the opposite direction, biasing means for urging the second fiyball mechanism toward the first fiyball mechanism, and a member movable in response to the movement of the second fiyball mechanism for opening the valve to admit fluid to the servo motor.

13. In an aircraft gun synchronizer, a driving shaft, a driven shaft, means for connecting the driving shaft to the driven shaft for rotative movement and movable to advance or retard the driven shaft with respect to the driving shaft, fluid'power means for moving the first said means, a valve for admitting fluid under pressure to the power means, a centrifugal control for said valve and power means, said control comprising a driving shaft, an axially movable sleeve mounted on said driving shaft, a first fiyball mechanism secured to the driving shaft and operative to move the sleeve axially, an axially movable second flyball mechanism rotatably connected to said driving shaft operative to tend to move said sleeve in the opposite direction, biasing means for urging the second fiyball mechanism toward the first fiyball mechanism, and a member movable in response to the movement of the second fiyball mechanism for opening the valve to admit fluid under pressure to the fluid power means.

14. In an aircraft gun synchronizer, a driving shaft, a driven shaft, axially movable means for connecting the driving shaft to the driven shaft for rotative movement and for advancing or retarding the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, a centrifugal control for said valve and power means, said control comprising a governor shaft driven by said driving shaft, an axially movable sleeve mounted thereon, a first fiyball mechanism secured to the governor shaft and operative to move the sleeve axially, an axially movable second fiyball mechanism rotatably connected to said governor shaft operative to tend to move said sleeve in the opposite direction, biasing means for urging the second fiyball mechanism toward the first fiyball mechanism, and a member movable in response to the movement of the second fiyball mechanism for opening the valve to admit fluid under pressureto the fluid power means.

15. In an aircraftgun synchronizer, a driving shaft, a driven shaft, axially movable means for connecting the driving shaft to the driven shaft for rotative movement and for advancing or retarding the driven shaft with respect to the driving shaft, fluid power means for moving the first said means, a valve for admitting fluid under pressure to the power means, said power means including a stationary piston and a cylinder movable in follow-up in accordance with the position of said valve, a centrifugal control for said valve and power means, said control comprising a driving shaft, an axially movable sleeve mounted on said driving shaft, a first fiyball mechanism secured to the driving shaft and operative to move the sleeve axially, an axially movable second flyball mechanism rotatably connected to said driving shaft operative to tend to move said sleeve in the opposite direction, biasing means for urging the second fiyball mechanism toward the first fiyball mechanism, and a member movable in response to the movement of the second flyball mechanism for opening the valve to admit fluid under pressure to the fluid power means.

16. A speed responsive device comprising a rotatable shaft, a centrifugal governor driven by the shaft and having a member axially movable upon variations in the speed of said shaft, a second centrifugal governor driven by the shaft and having a member axially movable upon variations in the speed of said shaft, a control element, and means operatively connecting said members to the element to move it in response to a given change in speed of said shaft but ineffective to move the element in response to change in acceleration of the speed device.

1?. A speed responsive device for use on a vehicle comprising a rotatable shaft, a pair of centrifugal governors driven by the shaft, and a trifugal governors driven by the shaft, a control element, and means connecting the governors to the element to operate said element, said governors and means being so arranged that inertia effects of one governor resulting from change in velocity of the vehicle tend to move the element in one direction and the inertia effects of the other governor tends to move the element in the opposite direction.

GEORGE W. PONTIUS, III.